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<h1 class="settitle">avconv Documentation</h1>
<a name="SEC_Contents"></a>
<h1>Table of Contents</h1>
<div class="contents">
<ul class="toc">
<li><a name="toc-Synopsis" href="#Synopsis">1. Synopsis</a></li>
<li><a name="toc-Description" href="#Description">2. Description</a></li>
<li><a name="toc-Detailed-description" href="#Detailed-description">3. Detailed description</a>
<ul class="toc">
<li><a name="toc-Filtering" href="#Filtering">3.1 Filtering</a>
<ul class="toc">
<li><a name="toc-Simple-filtergraphs" href="#Simple-filtergraphs">3.1.1 Simple filtergraphs</a></li>
<li><a name="toc-Complex-filtergraphs" href="#Complex-filtergraphs">3.1.2 Complex filtergraphs</a></li>
</ul></li>
<li><a name="toc-Stream-copy" href="#Stream-copy">3.2 Stream copy</a></li>
</ul></li>
<li><a name="toc-Stream-selection" href="#Stream-selection">4. Stream selection</a></li>
<li><a name="toc-Options-1" href="#Options-1">5. Options</a>
<ul class="toc">
<li><a name="toc-Stream-specifiers-1" href="#Stream-specifiers-1">5.1 Stream specifiers</a></li>
<li><a name="toc-Generic-options" href="#Generic-options">5.2 Generic options</a></li>
<li><a name="toc-AVOptions" href="#AVOptions">5.3 AVOptions</a></li>
<li><a name="toc-Codec-AVOptions" href="#Codec-AVOptions">5.4 Codec AVOptions</a></li>
<li><a name="toc-Format-AVOptions" href="#Format-AVOptions">5.5 Format AVOptions</a></li>
<li><a name="toc-Main-options" href="#Main-options">5.6 Main options</a></li>
<li><a name="toc-Video-Options" href="#Video-Options">5.7 Video Options</a></li>
<li><a name="toc-Advanced-Video-Options" href="#Advanced-Video-Options">5.8 Advanced Video Options</a></li>
<li><a name="toc-Audio-Options" href="#Audio-Options">5.9 Audio Options</a></li>
<li><a name="toc-Advanced-Audio-options_003a" href="#Advanced-Audio-options_003a">5.10 Advanced Audio options:</a></li>
<li><a name="toc-Subtitle-options_003a" href="#Subtitle-options_003a">5.11 Subtitle options:</a></li>
<li><a name="toc-Advanced-options" href="#Advanced-options">5.12 Advanced options</a></li>
</ul></li>
<li><a name="toc-Tips" href="#Tips">6. Tips</a></li>
<li><a name="toc-Examples-1" href="#Examples-1">7. Examples</a>
<ul class="toc">
<li><a name="toc-Preset-files" href="#Preset-files">7.1 Preset files</a></li>
<li><a name="toc-Video-and-Audio-grabbing" href="#Video-and-Audio-grabbing">7.2 Video and Audio grabbing</a></li>
<li><a name="toc-X11-grabbing" href="#X11-grabbing">7.3 X11 grabbing</a></li>
<li><a name="toc-Video-and-Audio-file-format-conversion" href="#Video-and-Audio-file-format-conversion">7.4 Video and Audio file format conversion</a></li>
</ul></li>
<li><a name="toc-Expression-Evaluation" href="#Expression-Evaluation">8. Expression Evaluation</a></li>
<li><a name="toc-Decoders" href="#Decoders">9. Decoders</a></li>
<li><a name="toc-Audio-Decoders" href="#Audio-Decoders">10. Audio Decoders</a>
<ul class="toc">
<li><a name="toc-ac3" href="#ac3">10.1 ac3</a>
<ul class="toc">
<ul class="toc">
<li><a name="toc-AC_002d3-Decoder-Options" href="#AC_002d3-Decoder-Options">10.1.0.1 AC-3 Decoder Options</a></li>
</ul>
</li>
</ul>
</li>
</ul></li>
<li><a name="toc-Encoders" href="#Encoders">11. Encoders</a></li>
<li><a name="toc-Audio-Encoders" href="#Audio-Encoders">12. Audio Encoders</a>
<ul class="toc">
<li><a name="toc-ac3-and-ac3_005ffixed" href="#ac3-and-ac3_005ffixed">12.1 ac3 and ac3_fixed</a>
<ul class="toc">
<li><a name="toc-AC_002d3-Metadata" href="#AC_002d3-Metadata">12.1.1 AC-3 Metadata</a>
<ul class="toc">
<li><a name="toc-Metadata-Control-Options" href="#Metadata-Control-Options">12.1.1.1 Metadata Control Options</a></li>
<li><a name="toc-Downmix-Levels" href="#Downmix-Levels">12.1.1.2 Downmix Levels</a></li>
<li><a name="toc-Audio-Production-Information" href="#Audio-Production-Information">12.1.1.3 Audio Production Information</a></li>
<li><a name="toc-Other-Metadata-Options" href="#Other-Metadata-Options">12.1.1.4 Other Metadata Options</a></li>
</ul></li>
<li><a name="toc-Extended-Bitstream-Information" href="#Extended-Bitstream-Information">12.1.2 Extended Bitstream Information</a>
<ul class="toc">
<li><a name="toc-Extended-Bitstream-Information-_002d-Part-1" href="#Extended-Bitstream-Information-_002d-Part-1">12.1.2.1 Extended Bitstream Information - Part 1</a></li>
<li><a name="toc-Extended-Bitstream-Information-_002d-Part-2" href="#Extended-Bitstream-Information-_002d-Part-2">12.1.2.2 Extended Bitstream Information - Part 2</a></li>
</ul></li>
<li><a name="toc-Other-AC_002d3-Encoding-Options" href="#Other-AC_002d3-Encoding-Options">12.1.3 Other AC-3 Encoding Options</a></li>
</ul></li>
<li><a name="toc-libwavpack" href="#libwavpack">12.2 libwavpack</a></li>
</ul></li>
<li><a name="toc-Video-Encoders" href="#Video-Encoders">13. Video Encoders</a>
<ul class="toc">
<li><a name="toc-libwebp" href="#libwebp">13.1 libwebp</a>
<ul class="toc">
<li><a name="toc-Pixel-Format" href="#Pixel-Format">13.1.1 Pixel Format</a></li>
<li><a name="toc-Options" href="#Options">13.1.2 Options</a></li>
</ul></li>
<li><a name="toc-libx264" href="#libx264">13.2 libx264</a>
<ul class="toc">
<li><a name="toc-Option-Mapping" href="#Option-Mapping">13.2.1 Option Mapping</a></li>
<li><a name="toc-Private-Options-1" href="#Private-Options-1">13.2.2 Private Options</a></li>
</ul></li>
<li><a name="toc-ProRes" href="#ProRes">13.3 ProRes</a>
<ul class="toc">
<li><a name="toc-Private-Options" href="#Private-Options">13.3.1 Private Options</a></li>
<li><a name="toc-Speed-considerations" href="#Speed-considerations">13.3.2 Speed considerations</a></li>
</ul>
</li>
</ul></li>
<li><a name="toc-Demuxers" href="#Demuxers">14. Demuxers</a>
<ul class="toc">
<li><a name="toc-image2-1" href="#image2-1">14.1 image2</a></li>
<li><a name="toc-applehttp" href="#applehttp">14.2 applehttp</a></li>
<li><a name="toc-flv" href="#flv">14.3 flv</a></li>
<li><a name="toc-asf" href="#asf">14.4 asf</a></li>
</ul></li>
<li><a name="toc-Muxers" href="#Muxers">15. Muxers</a>
<ul class="toc">
<li><a name="toc-crc-1" href="#crc-1">15.1 crc</a></li>
<li><a name="toc-framecrc-1" href="#framecrc-1">15.2 framecrc</a></li>
<li><a name="toc-hls-1" href="#hls-1">15.3 hls</a></li>
<li><a name="toc-image2-2" href="#image2-2">15.4 image2</a></li>
<li><a name="toc-matroska" href="#matroska">15.5 matroska</a></li>
<li><a name="toc-mov_002c-mp4_002c-ismv" href="#mov_002c-mp4_002c-ismv">15.6 mov, mp4, ismv</a></li>
<li><a name="toc-mp3" href="#mp3">15.7 mp3</a></li>
<li><a name="toc-mpegts" href="#mpegts">15.8 mpegts</a></li>
<li><a name="toc-null" href="#null">15.9 null</a></li>
<li><a name="toc-nut" href="#nut">15.10 nut</a></li>
<li><a name="toc-ogg" href="#ogg">15.11 ogg</a></li>
<li><a name="toc-segment" href="#segment">15.12 segment</a></li>
</ul></li>
<li><a name="toc-Input-Devices" href="#Input-Devices">16. Input Devices</a>
<ul class="toc">
<li><a name="toc-alsa-1" href="#alsa-1">16.1 alsa</a></li>
<li><a name="toc-bktr" href="#bktr">16.2 bktr</a></li>
<li><a name="toc-dv1394" href="#dv1394">16.3 dv1394</a></li>
<li><a name="toc-fbdev" href="#fbdev">16.4 fbdev</a></li>
<li><a name="toc-jack" href="#jack">16.5 jack</a></li>
<li><a name="toc-libdc1394" href="#libdc1394">16.6 libdc1394</a></li>
<li><a name="toc-oss-1" href="#oss-1">16.7 oss</a></li>
<li><a name="toc-pulse" href="#pulse">16.8 pulse</a>
<ul class="toc">
<li><a name="toc-server-AVOption" href="#server-AVOption">16.8.1 <var>server</var> AVOption</a></li>
<li><a name="toc-name-AVOption" href="#name-AVOption">16.8.2 <var>name</var> AVOption</a></li>
<li><a name="toc-stream_005fname-AVOption" href="#stream_005fname-AVOption">16.8.3 <var>stream_name</var> AVOption</a></li>
<li><a name="toc-sample_005frate-AVOption" href="#sample_005frate-AVOption">16.8.4 <var>sample_rate</var> AVOption</a></li>
<li><a name="toc-channels-AVOption" href="#channels-AVOption">16.8.5 <var>channels</var> AVOption</a></li>
<li><a name="toc-frame_005fsize-AVOption" href="#frame_005fsize-AVOption">16.8.6 <var>frame_size</var> AVOption</a></li>
<li><a name="toc-fragment_005fsize-AVOption" href="#fragment_005fsize-AVOption">16.8.7 <var>fragment_size</var> AVOption</a></li>
</ul></li>
<li><a name="toc-sndio-1" href="#sndio-1">16.9 sndio</a></li>
<li><a name="toc-video4linux2" href="#video4linux2">16.10 video4linux2</a></li>
<li><a name="toc-vfwcap" href="#vfwcap">16.11 vfwcap</a></li>
<li><a name="toc-x11grab" href="#x11grab">16.12 x11grab</a>
<ul class="toc">
<li><a name="toc-follow_005fmouse-AVOption" href="#follow_005fmouse-AVOption">16.12.1 <var>follow_mouse</var> AVOption</a></li>
<li><a name="toc-show_005fregion-AVOption" href="#show_005fregion-AVOption">16.12.2 <var>show_region</var> AVOption</a></li>
</ul>
</li>
</ul></li>
<li><a name="toc-Output-Devices" href="#Output-Devices">17. Output Devices</a>
<ul class="toc">
<li><a name="toc-alsa" href="#alsa">17.1 alsa</a></li>
<li><a name="toc-oss" href="#oss">17.2 oss</a></li>
<li><a name="toc-sndio" href="#sndio">17.3 sndio</a></li>
</ul></li>
<li><a name="toc-Protocols" href="#Protocols">18. Protocols</a>
<ul class="toc">
<li><a name="toc-concat" href="#concat">18.1 concat</a></li>
<li><a name="toc-file" href="#file">18.2 file</a></li>
<li><a name="toc-gopher" href="#gopher">18.3 gopher</a></li>
<li><a name="toc-hls-2" href="#hls-2">18.4 hls</a></li>
<li><a name="toc-http" href="#http">18.5 http</a></li>
<li><a name="toc-Icecast" href="#Icecast">18.6 Icecast</a></li>
<li><a name="toc-mmst" href="#mmst">18.7 mmst</a></li>
<li><a name="toc-mmsh" href="#mmsh">18.8 mmsh</a></li>
<li><a name="toc-md5" href="#md5">18.9 md5</a></li>
<li><a name="toc-pipe" href="#pipe">18.10 pipe</a></li>
<li><a name="toc-rtmp" href="#rtmp">18.11 rtmp</a></li>
<li><a name="toc-rtmpe" href="#rtmpe">18.12 rtmpe</a></li>
<li><a name="toc-rtmps" href="#rtmps">18.13 rtmps</a></li>
<li><a name="toc-rtmpt" href="#rtmpt">18.14 rtmpt</a></li>
<li><a name="toc-rtmpte" href="#rtmpte">18.15 rtmpte</a></li>
<li><a name="toc-rtmpts" href="#rtmpts">18.16 rtmpts</a></li>
<li><a name="toc-librtmp-rtmp_002c-rtmpe_002c-rtmps_002c-rtmpt_002c-rtmpte" href="#librtmp-rtmp_002c-rtmpe_002c-rtmps_002c-rtmpt_002c-rtmpte">18.17 librtmp rtmp, rtmpe, rtmps, rtmpt, rtmpte</a></li>
<li><a name="toc-rtp" href="#rtp">18.18 rtp</a></li>
<li><a name="toc-rtsp" href="#rtsp">18.19 rtsp</a></li>
<li><a name="toc-sap" href="#sap">18.20 sap</a>
<ul class="toc">
<li><a name="toc-Muxer" href="#Muxer">18.20.1 Muxer</a></li>
<li><a name="toc-Demuxer" href="#Demuxer">18.20.2 Demuxer</a></li>
</ul></li>
<li><a name="toc-tcp" href="#tcp">18.21 tcp</a></li>
<li><a name="toc-tls" href="#tls">18.22 tls</a></li>
<li><a name="toc-udp" href="#udp">18.23 udp</a></li>
<li><a name="toc-unix" href="#unix">18.24 unix</a></li>
</ul></li>
<li><a name="toc-Bitstream-Filters" href="#Bitstream-Filters">19. Bitstream Filters</a>
<ul class="toc">
<li><a name="toc-aac_005fadtstoasc" href="#aac_005fadtstoasc">19.1 aac_adtstoasc</a></li>
<li><a name="toc-chomp" href="#chomp">19.2 chomp</a></li>
<li><a name="toc-dump_005fextradata" href="#dump_005fextradata">19.3 dump_extradata</a></li>
<li><a name="toc-h264_005fmp4toannexb" href="#h264_005fmp4toannexb">19.4 h264_mp4toannexb</a></li>
<li><a name="toc-imx_005fdump_005fheader" href="#imx_005fdump_005fheader">19.5 imx_dump_header</a></li>
<li><a name="toc-mjpeg2jpeg" href="#mjpeg2jpeg">19.6 mjpeg2jpeg</a></li>
<li><a name="toc-mjpega_005fdump_005fheader" href="#mjpega_005fdump_005fheader">19.7 mjpega_dump_header</a></li>
<li><a name="toc-movsub" href="#movsub">19.8 movsub</a></li>
<li><a name="toc-mp3_005fheader_005fcompress" href="#mp3_005fheader_005fcompress">19.9 mp3_header_compress</a></li>
<li><a name="toc-mp3_005fheader_005fdecompress" href="#mp3_005fheader_005fdecompress">19.10 mp3_header_decompress</a></li>
<li><a name="toc-noise" href="#noise">19.11 noise</a></li>
<li><a name="toc-remove_005fextradata" href="#remove_005fextradata">19.12 remove_extradata</a></li>
</ul></li>
<li><a name="toc-Filtergraph-description" href="#Filtergraph-description">20. Filtergraph description</a>
<ul class="toc">
<li><a name="toc-Filtergraph-syntax-1" href="#Filtergraph-syntax-1">20.1 Filtergraph syntax</a></li>
</ul></li>
<li><a name="toc-Audio-Filters" href="#Audio-Filters">21. Audio Filters</a>
<ul class="toc">
<li><a name="toc-aformat" href="#aformat">21.1 aformat</a></li>
<li><a name="toc-amix" href="#amix">21.2 amix</a></li>
<li><a name="toc-anull" href="#anull">21.3 anull</a></li>
<li><a name="toc-asetpts" href="#asetpts">21.4 asetpts</a></li>
<li><a name="toc-asettb" href="#asettb">21.5 asettb</a></li>
<li><a name="toc-ashowinfo" href="#ashowinfo">21.6 ashowinfo</a></li>
<li><a name="toc-asplit" href="#asplit">21.7 asplit</a></li>
<li><a name="toc-asyncts" href="#asyncts">21.8 asyncts</a></li>
<li><a name="toc-atrim" href="#atrim">21.9 atrim</a></li>
<li><a name="toc-bs2b" href="#bs2b">21.10 bs2b</a></li>
<li><a name="toc-channelsplit" href="#channelsplit">21.11 channelsplit</a></li>
<li><a name="toc-channelmap" href="#channelmap">21.12 channelmap</a></li>
<li><a name="toc-compand" href="#compand">21.13 compand</a>
<ul class="toc">
<li><a name="toc-Examples" href="#Examples">21.13.1 Examples</a></li>
</ul></li>
<li><a name="toc-join" href="#join">21.14 join</a></li>
<li><a name="toc-resample" href="#resample">21.15 resample</a></li>
<li><a name="toc-volume" href="#volume">21.16 volume</a>
<ul class="toc">
<li><a name="toc-Examples-2" href="#Examples-2">21.16.1 Examples</a></li>
</ul>
</li>
</ul></li>
<li><a name="toc-Audio-Sources" href="#Audio-Sources">22. Audio Sources</a>
<ul class="toc">
<li><a name="toc-anullsrc" href="#anullsrc">22.1 anullsrc</a></li>
<li><a name="toc-abuffer" href="#abuffer">22.2 abuffer</a></li>
</ul></li>
<li><a name="toc-Audio-Sinks" href="#Audio-Sinks">23. Audio Sinks</a>
<ul class="toc">
<li><a name="toc-anullsink" href="#anullsink">23.1 anullsink</a></li>
<li><a name="toc-abuffersink" href="#abuffersink">23.2 abuffersink</a></li>
</ul></li>
<li><a name="toc-Video-Filters" href="#Video-Filters">24. Video Filters</a>
<ul class="toc">
<li><a name="toc-blackframe" href="#blackframe">24.1 blackframe</a></li>
<li><a name="toc-boxblur" href="#boxblur">24.2 boxblur</a></li>
<li><a name="toc-copy" href="#copy">24.3 copy</a></li>
<li><a name="toc-crop" href="#crop">24.4 crop</a></li>
<li><a name="toc-cropdetect" href="#cropdetect">24.5 cropdetect</a></li>
<li><a name="toc-delogo" href="#delogo">24.6 delogo</a></li>
<li><a name="toc-drawbox" href="#drawbox">24.7 drawbox</a></li>
<li><a name="toc-drawtext" href="#drawtext">24.8 drawtext</a></li>
<li><a name="toc-fade" href="#fade">24.9 fade</a></li>
<li><a name="toc-fieldorder" href="#fieldorder">24.10 fieldorder</a></li>
<li><a name="toc-fifo" href="#fifo">24.11 fifo</a></li>
<li><a name="toc-format" href="#format">24.12 format</a></li>
<li><a name="toc-fps-1" href="#fps-1">24.13 fps</a></li>
<li><a name="toc-framepack" href="#framepack">24.14 framepack</a></li>
<li><a name="toc-frei0r-1" href="#frei0r-1">24.15 frei0r</a></li>
<li><a name="toc-gradfun" href="#gradfun">24.16 gradfun</a></li>
<li><a name="toc-hflip" href="#hflip">24.17 hflip</a></li>
<li><a name="toc-hqdn3d" href="#hqdn3d">24.18 hqdn3d</a></li>
<li><a name="toc-interlace" href="#interlace">24.19 interlace</a></li>
<li><a name="toc-lut_002c-lutrgb_002c-lutyuv" href="#lut_002c-lutrgb_002c-lutyuv">24.20 lut, lutrgb, lutyuv</a></li>
<li><a name="toc-negate" href="#negate">24.21 negate</a></li>
<li><a name="toc-noformat" href="#noformat">24.22 noformat</a></li>
<li><a name="toc-null-1" href="#null-1">24.23 null</a></li>
<li><a name="toc-ocv" href="#ocv">24.24 ocv</a>
<ul class="toc">
<li><a name="toc-dilate-1" href="#dilate-1">24.24.1 dilate</a></li>
<li><a name="toc-erode" href="#erode">24.24.2 erode</a></li>
<li><a name="toc-smooth" href="#smooth">24.24.3 smooth</a></li>
</ul></li>
<li><a name="toc-overlay-1" href="#overlay-1">24.25 overlay</a></li>
<li><a name="toc-pad" href="#pad">24.26 pad</a></li>
<li><a name="toc-pixdesctest" href="#pixdesctest">24.27 pixdesctest</a></li>
<li><a name="toc-scale-1" href="#scale-1">24.28 scale</a></li>
<li><a name="toc-select" href="#select">24.29 select</a></li>
<li><a name="toc-setdar-1" href="#setdar-1">24.30 setdar</a></li>
<li><a name="toc-setpts" href="#setpts">24.31 setpts</a></li>
<li><a name="toc-setsar-1" href="#setsar-1">24.32 setsar</a></li>
<li><a name="toc-settb" href="#settb">24.33 settb</a></li>
<li><a name="toc-showinfo" href="#showinfo">24.34 showinfo</a></li>
<li><a name="toc-shuffleplanes" href="#shuffleplanes">24.35 shuffleplanes</a></li>
<li><a name="toc-split" href="#split">24.36 split</a></li>
<li><a name="toc-transpose" href="#transpose">24.37 transpose</a></li>
<li><a name="toc-trim" href="#trim">24.38 trim</a></li>
<li><a name="toc-unsharp" href="#unsharp">24.39 unsharp</a></li>
<li><a name="toc-vflip" href="#vflip">24.40 vflip</a></li>
<li><a name="toc-yadif" href="#yadif">24.41 yadif</a></li>
</ul></li>
<li><a name="toc-Video-Sources" href="#Video-Sources">25. Video Sources</a>
<ul class="toc">
<li><a name="toc-buffer" href="#buffer">25.1 buffer</a></li>
<li><a name="toc-color" href="#color">25.2 color</a></li>
<li><a name="toc-movie" href="#movie">25.3 movie</a></li>
<li><a name="toc-nullsrc" href="#nullsrc">25.4 nullsrc</a></li>
<li><a name="toc-frei0r_005fsrc" href="#frei0r_005fsrc">25.5 frei0r_src</a></li>
<li><a name="toc-rgbtestsrc_002c-testsrc" href="#rgbtestsrc_002c-testsrc">25.6 rgbtestsrc, testsrc</a></li>
</ul></li>
<li><a name="toc-Video-Sinks" href="#Video-Sinks">26. Video Sinks</a>
<ul class="toc">
<li><a name="toc-buffersink" href="#buffersink">26.1 buffersink</a></li>
<li><a name="toc-nullsink" href="#nullsink">26.2 nullsink</a></li>
</ul></li>
<li><a name="toc-Metadata" href="#Metadata">27. Metadata</a></li>
</ul>
</div>
<a name="Synopsis"></a>
<h1 class="chapter"><a href="avconv.html#toc-Synopsis">1. Synopsis</a></h1>
<p>The generic syntax is:
</p>
<table><tr><td> </td><td><pre class="example">avconv [global options] [[infile options][‘<samp>-i</samp>’ <var>infile</var>]]... {[outfile options] <var>outfile</var>}...
</pre></td></tr></table>
<a name="Description"></a>
<h1 class="chapter"><a href="avconv.html#toc-Description">2. Description</a></h1>
<p>avconv is a very fast video and audio converter that can also grab from
a live audio/video source. It can also convert between arbitrary sample
rates and resize video on the fly with a high quality polyphase filter.
</p>
<p>avconv reads from an arbitrary number of input "files" (which can be regular
files, pipes, network streams, grabbing devices, etc.), specified by the
<code>-i</code> option, and writes to an arbitrary number of output "files", which are
specified by a plain output filename. Anything found on the command line which
cannot be interpreted as an option is considered to be an output filename.
</p>
<p>Each input or output file can in principle contain any number of streams of
different types (video/audio/subtitle/attachment/data). Allowed number and/or
types of streams can be limited by the container format. Selecting, which
streams from which inputs go into output, is done either automatically or with
the <code>-map</code> option (see the Stream selection chapter).
</p>
<p>To refer to input files in options, you must use their indices (0-based). E.g.
the first input file is <code>0</code>, the second is <code>1</code> etc. Similarly, streams
within a file are referred to by their indices. E.g. <code>2:3</code> refers to the
fourth stream in the third input file. See also the Stream specifiers chapter.
</p>
<p>As a general rule, options are applied to the next specified
file. Therefore, order is important, and you can have the same
option on the command line multiple times. Each occurrence is
then applied to the next input or output file.
Exceptions from this rule are the global options (e.g. verbosity level),
which should be specified first.
</p>
<p>Do not mix input and output files – first specify all input files, then all
output files. Also do not mix options which belong to different files. All
options apply ONLY to the next input or output file and are reset between files.
</p>
<ul>
<li>
To set the video bitrate of the output file to 64kbit/s:
<table><tr><td> </td><td><pre class="example">avconv -i input.avi -b 64k output.avi
</pre></td></tr></table>
</li><li>
To force the frame rate of the output file to 24 fps:
<table><tr><td> </td><td><pre class="example">avconv -i input.avi -r 24 output.avi
</pre></td></tr></table>
</li><li>
To force the frame rate of the input file (valid for raw formats only)
to 1 fps and the frame rate of the output file to 24 fps:
<table><tr><td> </td><td><pre class="example">avconv -r 1 -i input.m2v -r 24 output.avi
</pre></td></tr></table>
</li></ul>
<p>The format option may be needed for raw input files.
</p>
<a name="Detailed-description"></a>
<h1 class="chapter"><a href="avconv.html#toc-Detailed-description">3. Detailed description</a></h1>
<p>The transcoding process in <code>avconv</code> for each output can be described by
the following diagram:
</p>
<table><tr><td> </td><td><pre class="example"> _______ ______________
| | | |
| input | demuxer | encoded data | decoder
| file | ---------> | packets | -----+
|_______| |______________| |
v
_________
| |
| decoded |
| frames |
|_________|
________ ______________ |
| | | | |
| output | <-------- | encoded data | <----+
| file | muxer | packets | encoder
|________| |______________|
</pre></td></tr></table>
<p><code>avconv</code> calls the libavformat library (containing demuxers) to read
input files and get packets containing encoded data from them. When there are
multiple input files, <code>avconv</code> tries to keep them synchronized by
tracking lowest timestamp on any active input stream.
</p>
<p>Encoded packets are then passed to the decoder (unless streamcopy is selected
for the stream, see further for a description). The decoder produces
uncompressed frames (raw video/PCM audio/...) which can be processed further by
filtering (see next section). After filtering the frames are passed to the
encoder, which encodes them and outputs encoded packets again. Finally those are
passed to the muxer, which writes the encoded packets to the output file.
</p>
<a name="Filtering"></a>
<h2 class="section"><a href="avconv.html#toc-Filtering">3.1 Filtering</a></h2>
<p>Before encoding, <code>avconv</code> can process raw audio and video frames using
filters from the libavfilter library. Several chained filters form a filter
graph. <code>avconv</code> distinguishes between two types of filtergraphs -
simple and complex.
</p>
<a name="Simple-filtergraphs"></a>
<h3 class="subsection"><a href="avconv.html#toc-Simple-filtergraphs">3.1.1 Simple filtergraphs</a></h3>
<p>Simple filtergraphs are those that have exactly one input and output, both of
the same type. In the above diagram they can be represented by simply inserting
an additional step between decoding and encoding:
</p>
<table><tr><td> </td><td><pre class="example"> _________ ______________
| | | |
| decoded | | encoded data |
| frames |\ /| packets |
|_________| \ / |______________|
\ __________ /
simple \ | | / encoder
filtergraph \| filtered |/
| frames |
|__________|
</pre></td></tr></table>
<p>Simple filtergraphs are configured with the per-stream ‘<samp>-filter</samp>’ option
(with ‘<samp>-vf</samp>’ and ‘<samp>-af</samp>’ aliases for video and audio respectively).
A simple filtergraph for video can look for example like this:
</p>
<table><tr><td> </td><td><pre class="example"> _______ _____________ _______ ________
| | | | | | | |
| input | ---> | deinterlace | ---> | scale | ---> | output |
|_______| |_____________| |_______| |________|
</pre></td></tr></table>
<p>Note that some filters change frame properties but not frame contents. E.g. the
<code>fps</code> filter in the example above changes number of frames, but does not
touch the frame contents. Another example is the <code>setpts</code> filter, which
only sets timestamps and otherwise passes the frames unchanged.
</p>
<a name="Complex-filtergraphs"></a>
<h3 class="subsection"><a href="avconv.html#toc-Complex-filtergraphs">3.1.2 Complex filtergraphs</a></h3>
<p>Complex filtergraphs are those which cannot be described as simply a linear
processing chain applied to one stream. This is the case e.g. when the graph has
more than one input and/or output, or when output stream type is different from
input. They can be represented with the following diagram:
</p>
<table><tr><td> </td><td><pre class="example"> _________
| |
| input 0 |\ __________
|_________| \ | |
\ _________ /| output 0 |
\ | | / |__________|
_________ \| complex | /
| | | |/
| input 1 |---->| filter |\
|_________| | | \ __________
/| graph | \ | |
/ | | \| output 1 |
_________ / |_________| |__________|
| | /
| input 2 |/
|_________|
</pre></td></tr></table>
<p>Complex filtergraphs are configured with the ‘<samp>-filter_complex</samp>’ option.
Note that this option is global, since a complex filtergraph by its nature
cannot be unambiguously associated with a single stream or file.
</p>
<p>A trivial example of a complex filtergraph is the <code>overlay</code> filter, which
has two video inputs and one video output, containing one video overlaid on top
of the other. Its audio counterpart is the <code>amix</code> filter.
</p>
<a name="Stream-copy"></a>
<h2 class="section"><a href="avconv.html#toc-Stream-copy">3.2 Stream copy</a></h2>
<p>Stream copy is a mode selected by supplying the <code>copy</code> parameter to the
‘<samp>-codec</samp>’ option. It makes <code>avconv</code> omit the decoding and encoding
step for the specified stream, so it does only demuxing and muxing. It is useful
for changing the container format or modifying container-level metadata. The
diagram above will in this case simplify to this:
</p>
<table><tr><td> </td><td><pre class="example"> _______ ______________ ________
| | | | | |
| input | demuxer | encoded data | muxer | output |
| file | ---------> | packets | -------> | file |
|_______| |______________| |________|
</pre></td></tr></table>
<p>Since there is no decoding or encoding, it is very fast and there is no quality
loss. However it might not work in some cases because of many factors. Applying
filters is obviously also impossible, since filters work on uncompressed data.
</p>
<a name="Stream-selection"></a>
<h1 class="chapter"><a href="avconv.html#toc-Stream-selection">4. Stream selection</a></h1>
<p>By default avconv tries to pick the "best" stream of each type present in input
files and add them to each output file. For video, this means the highest
resolution, for audio the highest channel count. For subtitle it’s simply the
first subtitle stream.
</p>
<p>You can disable some of those defaults by using <code>-vn/-an/-sn</code> options. For
full manual control, use the <code>-map</code> option, which disables the defaults just
described.
</p>
<a name="Options-1"></a>
<h1 class="chapter"><a href="avconv.html#toc-Options-1">5. Options</a></h1>
<p>All the numerical options, if not specified otherwise, accept in input
a string representing a number, which may contain one of the
SI unit prefixes, for example ’K’, ’M’, ’G’.
If ’i’ is appended after the prefix, binary prefixes are used,
which are based on powers of 1024 instead of powers of 1000.
The ’B’ postfix multiplies the value by 8, and can be
appended after a unit prefix or used alone. This allows using for
example ’KB’, ’MiB’, ’G’ and ’B’ as number postfix.
</p>
<p>Options which do not take arguments are boolean options, and set the
corresponding value to true. They can be set to false by prefixing
with "no" the option name, for example using "-nofoo" in the
command line will set to false the boolean option with name "foo".
</p>
<p><a name="Stream-specifiers"></a>
</p><a name="Stream-specifiers-1"></a>
<h2 class="section"><a href="avconv.html#toc-Stream-specifiers-1">5.1 Stream specifiers</a></h2>
<p>Some options are applied per-stream, e.g. bitrate or codec. Stream specifiers
are used to precisely specify which stream(s) does a given option belong to.
</p>
<p>A stream specifier is a string generally appended to the option name and
separated from it by a colon. E.g. <code>-codec:a:1 ac3</code> option contains
<code>a:1</code> stream specifer, which matches the second audio stream. Therefore it
would select the ac3 codec for the second audio stream.
</p>
<p>A stream specifier can match several stream, the option is then applied to all
of them. E.g. the stream specifier in <code>-b:a 128k</code> matches all audio
streams.
</p>
<p>An empty stream specifier matches all streams, for example <code>-codec copy</code>
or <code>-codec: copy</code> would copy all the streams without reencoding.
</p>
<p>Possible forms of stream specifiers are:
</p><dl compact="compact">
<dt> ‘<samp><var>stream_index</var></samp>’</dt>
<dd><p>Matches the stream with this index. E.g. <code>-threads:1 4</code> would set the
thread count for the second stream to 4.
</p></dd>
<dt> ‘<samp><var>stream_type</var>[:<var>stream_index</var>]</samp>’</dt>
<dd><p><var>stream_type</var> is one of: ’v’ for video, ’a’ for audio, ’s’ for subtitle,
’d’ for data and ’t’ for attachments. If <var>stream_index</var> is given, then
matches stream number <var>stream_index</var> of this type. Otherwise matches all
streams of this type.
</p></dd>
<dt> ‘<samp>p:<var>program_id</var>[:<var>stream_index</var>]</samp>’</dt>
<dd><p>If <var>stream_index</var> is given, then matches stream number <var>stream_index</var> in
program with id <var>program_id</var>. Otherwise matches all streams in this program.
</p></dd>
<dt> ‘<samp>i:<var>stream_id</var></samp>’</dt>
<dd><p>Match the stream by stream id (e.g. PID in MPEG-TS container).
</p></dd>
<dt> ‘<samp>m:<var>key</var>[:<var>value</var>]</samp>’</dt>
<dd><p>Matches streams with the metadata tag <var>key</var> having the specified value. If
<var>value</var> is not given, matches streams that contain the given tag with any
value.
</p>
<p>Note that in <code>avconv</code>, matching by metadata will only work properly for
input files.
</p></dd>
</dl>
<a name="Generic-options"></a>
<h2 class="section"><a href="avconv.html#toc-Generic-options">5.2 Generic options</a></h2>
<p>These options are shared amongst the av* tools.
</p>
<dl compact="compact">
<dt> ‘<samp>-L</samp>’</dt>
<dd><p>Show license.
</p>
</dd>
<dt> ‘<samp>-h, -?, -help, --help [<var>arg</var>]</samp>’</dt>
<dd><p>Show help. An optional parameter may be specified to print help about a specific
item.
</p>
<p>Possible values of <var>arg</var> are:
</p><dl compact="compact">
<dt> ‘<samp>decoder=<var>decoder_name</var></samp>’</dt>
<dd><p>Print detailed information about the decoder named <var>decoder_name</var>. Use the
‘<samp>-decoders</samp>’ option to get a list of all decoders.
</p>
</dd>
<dt> ‘<samp>encoder=<var>encoder_name</var></samp>’</dt>
<dd><p>Print detailed information about the encoder named <var>encoder_name</var>. Use the
‘<samp>-encoders</samp>’ option to get a list of all encoders.
</p>
</dd>
<dt> ‘<samp>demuxer=<var>demuxer_name</var></samp>’</dt>
<dd><p>Print detailed information about the demuxer named <var>demuxer_name</var>. Use the
‘<samp>-formats</samp>’ option to get a list of all demuxers and muxers.
</p>
</dd>
<dt> ‘<samp>muxer=<var>muxer_name</var></samp>’</dt>
<dd><p>Print detailed information about the muxer named <var>muxer_name</var>. Use the
‘<samp>-formats</samp>’ option to get a list of all muxers and demuxers.
</p>
</dd>
<dt> ‘<samp>filter=<var>filter_name</var></samp>’</dt>
<dd><p>Print detailed information about the filter name <var>filter_name</var>. Use the
‘<samp>-filters</samp>’ option to get a list of all filters.
</p>
</dd>
</dl>
</dd>
<dt> ‘<samp>-version</samp>’</dt>
<dd><p>Show version.
</p>
</dd>
<dt> ‘<samp>-formats</samp>’</dt>
<dd><p>Show available formats.
</p>
<p>The fields preceding the format names have the following meanings:
</p><dl compact="compact">
<dt> ‘<samp>D</samp>’</dt>
<dd><p>Decoding available
</p></dd>
<dt> ‘<samp>E</samp>’</dt>
<dd><p>Encoding available
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-codecs</samp>’</dt>
<dd><p>Show all codecs known to libavcodec.
</p>
<p>Note that the term ’codec’ is used throughout this documentation as a shortcut
for what is more correctly called a media bitstream format.
</p>
</dd>
<dt> ‘<samp>-decoders</samp>’</dt>
<dd><p>Show available decoders.
</p>
</dd>
<dt> ‘<samp>-encoders</samp>’</dt>
<dd><p>Show all available encoders.
</p>
</dd>
<dt> ‘<samp>-bsfs</samp>’</dt>
<dd><p>Show available bitstream filters.
</p>
</dd>
<dt> ‘<samp>-protocols</samp>’</dt>
<dd><p>Show available protocols.
</p>
</dd>
<dt> ‘<samp>-filters</samp>’</dt>
<dd><p>Show available libavfilter filters.
</p>
</dd>
<dt> ‘<samp>-pix_fmts</samp>’</dt>
<dd><p>Show available pixel formats.
</p>
</dd>
<dt> ‘<samp>-sample_fmts</samp>’</dt>
<dd><p>Show available sample formats.
</p>
</dd>
<dt> ‘<samp>-loglevel <var>loglevel</var> | -v <var>loglevel</var></samp>’</dt>
<dd><p>Set the logging level used by the library.
<var>loglevel</var> is a number or a string containing one of the following values:
</p><dl compact="compact">
<dt> ‘<samp>quiet</samp>’</dt>
<dt> ‘<samp>panic</samp>’</dt>
<dt> ‘<samp>fatal</samp>’</dt>
<dt> ‘<samp>error</samp>’</dt>
<dt> ‘<samp>warning</samp>’</dt>
<dt> ‘<samp>info</samp>’</dt>
<dt> ‘<samp>verbose</samp>’</dt>
<dt> ‘<samp>debug</samp>’</dt>
</dl>
<p>By default the program logs to stderr, if coloring is supported by the
terminal, colors are used to mark errors and warnings. Log coloring
can be disabled setting the environment variable
<code>AV_LOG_FORCE_NOCOLOR</code> or <code>NO_COLOR</code>, or can be forced setting
the environment variable <code>AV_LOG_FORCE_COLOR</code>.
The use of the environment variable <code>NO_COLOR</code> is deprecated and
will be dropped in a following Libav version.
</p>
</dd>
<dt> ‘<samp>-cpuflags mask (<em>global</em>)</samp>’</dt>
<dd><p>Set a mask that’s applied to autodetected CPU flags. This option is intended
for testing. Do not use it unless you know what you’re doing.
</p>
</dd>
</dl>
<a name="AVOptions"></a>
<h2 class="section"><a href="avconv.html#toc-AVOptions">5.3 AVOptions</a></h2>
<p>These options are provided directly by the libavformat, libavdevice and
libavcodec libraries. To see the list of available AVOptions, use the
‘<samp>-help</samp>’ option. They are separated into two categories:
</p><dl compact="compact">
<dt> ‘<samp>generic</samp>’</dt>
<dd><p>These options can be set for any container, codec or device. Generic options
are listed under AVFormatContext options for containers/devices and under
AVCodecContext options for codecs.
</p></dd>
<dt> ‘<samp>private</samp>’</dt>
<dd><p>These options are specific to the given container, device or codec. Private
options are listed under their corresponding containers/devices/codecs.
</p></dd>
</dl>
<p>For example to write an ID3v2.3 header instead of a default ID3v2.4 to
an MP3 file, use the ‘<samp>id3v2_version</samp>’ private option of the MP3
muxer:
</p><table><tr><td> </td><td><pre class="example">avconv -i input.flac -id3v2_version 3 out.mp3
</pre></td></tr></table>
<p>All codec AVOptions are obviously per-stream, so the chapter on stream
specifiers applies to them
</p>
<p>Note ‘<samp>-nooption</samp>’ syntax cannot be used for boolean AVOptions,
use ‘<samp>-option 0</samp>’/‘<samp>-option 1</samp>’.
</p>
<p>Note2 old undocumented way of specifying per-stream AVOptions by prepending
v/a/s to the options name is now obsolete and will be removed soon.
</p>
<a name="Codec-AVOptions"></a>
<h2 class="section"><a href="avconv.html#toc-Codec-AVOptions">5.4 Codec AVOptions</a></h2>
<dl compact="compact">
<dt> ‘<samp>-b[:stream_specifier] <var>integer</var> (<em>output,audio,video</em>)</samp>’</dt>
<dd><p>set bitrate (in bits/s)
</p></dd>
<dt> ‘<samp>-bt[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>Set video bitrate tolerance (in bits/s). In 1-pass mode, bitrate tolerance specifies how far ratecontrol is willing to deviate from the target average bitrate value. This is not related to minimum/maximum bitrate. Lowering tolerance too much has an adverse effect on quality.
</p></dd>
<dt> ‘<samp>-flags[:stream_specifier] <var>flags</var> (<em>input/output,audio,video</em>)</samp>’</dt>
<dd>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>unaligned</samp>’</dt>
<dd><p>allow decoders to produce unaligned output
</p></dd>
<dt> ‘<samp>mv4</samp>’</dt>
<dd><p>use four motion vectors per macroblock (MPEG-4)
</p></dd>
<dt> ‘<samp>qpel</samp>’</dt>
<dd><p>use 1/4-pel motion compensation
</p></dd>
<dt> ‘<samp>loop</samp>’</dt>
<dd><p>use loop filter
</p></dd>
<dt> ‘<samp>qscale</samp>’</dt>
<dd><p>use fixed qscale
</p></dd>
<dt> ‘<samp>gmc</samp>’</dt>
<dd><p>use gmc
</p></dd>
<dt> ‘<samp>mv0</samp>’</dt>
<dd><p>always try a mb with mv=<0,0>
</p></dd>
<dt> ‘<samp>input_preserved</samp>’</dt>
<dt> ‘<samp>pass1</samp>’</dt>
<dd><p>use internal 2-pass ratecontrol in first pass mode
</p></dd>
<dt> ‘<samp>pass2</samp>’</dt>
<dd><p>use internal 2-pass ratecontrol in second pass mode
</p></dd>
<dt> ‘<samp>gray</samp>’</dt>
<dd><p>only decode/encode grayscale
</p></dd>
<dt> ‘<samp>emu_edge</samp>’</dt>
<dd><p>do not draw edges
</p></dd>
<dt> ‘<samp>psnr</samp>’</dt>
<dd><p>error[?] variables will be set during encoding
</p></dd>
<dt> ‘<samp>truncated</samp>’</dt>
<dt> ‘<samp>naq</samp>’</dt>
<dd><p>normalize adaptive quantization
</p></dd>
<dt> ‘<samp>ildct</samp>’</dt>
<dd><p>use interlaced DCT
</p></dd>
<dt> ‘<samp>low_delay</samp>’</dt>
<dd><p>force low delay
</p></dd>
<dt> ‘<samp>global_header</samp>’</dt>
<dd><p>place global headers in extradata instead of every keyframe
</p></dd>
<dt> ‘<samp>bitexact</samp>’</dt>
<dd><p>use only bitexact functions (except (I)DCT)
</p></dd>
<dt> ‘<samp>aic</samp>’</dt>
<dd><p>H.263 advanced intra coding / MPEG-4 AC prediction
</p></dd>
<dt> ‘<samp>ilme</samp>’</dt>
<dd><p>interlaced motion estimation
</p></dd>
<dt> ‘<samp>cgop</samp>’</dt>
<dd><p>closed GOP
</p></dd>
<dt> ‘<samp>output_corrupt</samp>’</dt>
<dd><p>Output even potentially corrupted frames
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-me_method[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>set motion estimation method
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>zero</samp>’</dt>
<dd><p>zero motion estimation (fastest)
</p></dd>
<dt> ‘<samp>full</samp>’</dt>
<dd><p>full motion estimation (slowest)
</p></dd>
<dt> ‘<samp>epzs</samp>’</dt>
<dd><p>EPZS motion estimation (default)
</p></dd>
<dt> ‘<samp>esa</samp>’</dt>
<dd><p>esa motion estimation (alias for full)
</p></dd>
<dt> ‘<samp>tesa</samp>’</dt>
<dd><p>tesa motion estimation
</p></dd>
<dt> ‘<samp>dia</samp>’</dt>
<dd><p>diamond motion estimation (alias for EPZS)
</p></dd>
<dt> ‘<samp>log</samp>’</dt>
<dd><p>log motion estimation
</p></dd>
<dt> ‘<samp>phods</samp>’</dt>
<dd><p>phods motion estimation
</p></dd>
<dt> ‘<samp>x1</samp>’</dt>
<dd><p>X1 motion estimation
</p></dd>
<dt> ‘<samp>hex</samp>’</dt>
<dd><p>hex motion estimation
</p></dd>
<dt> ‘<samp>umh</samp>’</dt>
<dd><p>umh motion estimation
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-g[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>set the group of picture (GOP) size
</p></dd>
<dt> ‘<samp>-ar[:stream_specifier] <var>integer</var> (<em>input/output,audio</em>)</samp>’</dt>
<dd><p>set audio sampling rate (in Hz)
</p></dd>
<dt> ‘<samp>-ac[:stream_specifier] <var>integer</var> (<em>input/output,audio</em>)</samp>’</dt>
<dd><p>set number of audio channels
</p></dd>
<dt> ‘<samp>-cutoff[:stream_specifier] <var>integer</var> (<em>output,audio</em>)</samp>’</dt>
<dd><p>set cutoff bandwidth
</p></dd>
<dt> ‘<samp>-frame_size[:stream_specifier] <var>integer</var> (<em>output,audio</em>)</samp>’</dt>
<dt> ‘<samp>-qcomp[:stream_specifier] <var>float</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>video quantizer scale compression (VBR). Constant of ratecontrol equation. Recommended range for default rc_eq: 0.0-1.0
</p></dd>
<dt> ‘<samp>-qblur[:stream_specifier] <var>float</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>video quantizer scale blur (VBR)
</p></dd>
<dt> ‘<samp>-qmin[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>minimum video quantizer scale (VBR)
</p></dd>
<dt> ‘<samp>-qmax[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>maximum video quantizer scale (VBR)
</p></dd>
<dt> ‘<samp>-qdiff[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>maximum difference between the quantizer scales (VBR)
</p></dd>
<dt> ‘<samp>-bf[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>use ’frames’ B frames
</p></dd>
<dt> ‘<samp>-b_qfactor[:stream_specifier] <var>float</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>QP factor between P- and B-frames
</p></dd>
<dt> ‘<samp>-rc_strategy[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>ratecontrol method
</p></dd>
<dt> ‘<samp>-b_strategy[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>strategy to choose between I/P/B-frames
</p></dd>
<dt> ‘<samp>-ps[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>RTP payload size in bytes
</p></dd>
<dt> ‘<samp>-bug[:stream_specifier] <var>flags</var> (<em>input,video</em>)</samp>’</dt>
<dd><p>work around not autodetected encoder bugs
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>autodetect</samp>’</dt>
<dt> ‘<samp>old_msmpeg4</samp>’</dt>
<dd><p>some old lavc-generated MSMPEG4v3 files (no autodetection)
</p></dd>
<dt> ‘<samp>xvid_ilace</samp>’</dt>
<dd><p>Xvid interlacing bug (autodetected if FOURCC == XVIX)
</p></dd>
<dt> ‘<samp>ump4</samp>’</dt>
<dd><p>(autodetected if FOURCC == UMP4)
</p></dd>
<dt> ‘<samp>no_padding</samp>’</dt>
<dd><p>padding bug (autodetected)
</p></dd>
<dt> ‘<samp>amv</samp>’</dt>
<dt> ‘<samp>ac_vlc</samp>’</dt>
<dd><p>illegal VLC bug (autodetected per FOURCC)
</p></dd>
<dt> ‘<samp>qpel_chroma</samp>’</dt>
<dt> ‘<samp>std_qpel</samp>’</dt>
<dd><p>old standard qpel (autodetected per FOURCC/version)
</p></dd>
<dt> ‘<samp>qpel_chroma2</samp>’</dt>
<dt> ‘<samp>direct_blocksize</samp>’</dt>
<dd><p>direct-qpel-blocksize bug (autodetected per FOURCC/version)
</p></dd>
<dt> ‘<samp>edge</samp>’</dt>
<dd><p>edge padding bug (autodetected per FOURCC/version)
</p></dd>
<dt> ‘<samp>hpel_chroma</samp>’</dt>
<dt> ‘<samp>dc_clip</samp>’</dt>
<dt> ‘<samp>ms</samp>’</dt>
<dd><p>work around various bugs in Microsoft’s broken decoders
</p></dd>
<dt> ‘<samp>trunc</samp>’</dt>
<dd><p>truncated frames
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-strict[:stream_specifier] <var>integer</var> (<em>input/output,audio,video</em>)</samp>’</dt>
<dd><p>how strictly to follow the standards
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>very</samp>’</dt>
<dd><p>strictly conform to a older more strict version of the spec or reference software
</p></dd>
<dt> ‘<samp>strict</samp>’</dt>
<dd><p>strictly conform to all the things in the spec no matter what the consequences
</p></dd>
<dt> ‘<samp>normal</samp>’</dt>
<dt> ‘<samp>unofficial</samp>’</dt>
<dd><p>allow unofficial extensions
</p></dd>
<dt> ‘<samp>experimental</samp>’</dt>
<dd><p>allow non-standardized experimental things
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-b_qoffset[:stream_specifier] <var>float</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>QP offset between P- and B-frames
</p></dd>
<dt> ‘<samp>-err_detect[:stream_specifier] <var>flags</var> (<em>input,audio,video</em>)</samp>’</dt>
<dd><p>set error detection flags
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>crccheck</samp>’</dt>
<dd><p>verify embedded CRCs
</p></dd>
<dt> ‘<samp>bitstream</samp>’</dt>
<dd><p>detect bitstream specification deviations
</p></dd>
<dt> ‘<samp>buffer</samp>’</dt>
<dd><p>detect improper bitstream length
</p></dd>
<dt> ‘<samp>explode</samp>’</dt>
<dd><p>abort decoding on minor error detection
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-mpeg_quant[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>use MPEG quantizers instead of H.263
</p></dd>
<dt> ‘<samp>-qsquish[:stream_specifier] <var>float</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>how to keep quantizer between qmin and qmax (0 = clip, 1 = use differentiable function)
</p></dd>
<dt> ‘<samp>-rc_qmod_amp[:stream_specifier] <var>float</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>experimental quantizer modulation
</p></dd>
<dt> ‘<samp>-rc_qmod_freq[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>experimental quantizer modulation
</p></dd>
<dt> ‘<samp>-rc_eq[:stream_specifier] <var>string</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>Set rate control equation. When computing the expression, besides the standard functions defined in the section ’Expression Evaluation’, the following functions are available: bits2qp(bits), qp2bits(qp). Also the following constants are available: iTex pTex tex mv fCode iCount mcVar var isI isP isB avgQP qComp avgIITex avgPITex avgPPTex avgBPTex avgTex.
</p></dd>
<dt> ‘<samp>-maxrate[:stream_specifier] <var>integer</var> (<em>output,audio,video</em>)</samp>’</dt>
<dd><p>Set maximum bitrate tolerance (in bits/s). Requires bufsize to be set.
</p></dd>
<dt> ‘<samp>-minrate[:stream_specifier] <var>integer</var> (<em>output,audio,video</em>)</samp>’</dt>
<dd><p>Set minimum bitrate tolerance (in bits/s). Most useful in setting up a CBR encode. It is of little use otherwise.
</p></dd>
<dt> ‘<samp>-bufsize[:stream_specifier] <var>integer</var> (<em>output,audio,video</em>)</samp>’</dt>
<dd><p>set ratecontrol buffer size (in bits)
</p></dd>
<dt> ‘<samp>-rc_buf_aggressivity[:stream_specifier] <var>float</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>currently useless
</p></dd>
<dt> ‘<samp>-i_qfactor[:stream_specifier] <var>float</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>QP factor between P- and I-frames
</p></dd>
<dt> ‘<samp>-i_qoffset[:stream_specifier] <var>float</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>QP offset between P- and I-frames
</p></dd>
<dt> ‘<samp>-rc_init_cplx[:stream_specifier] <var>float</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>initial complexity for 1-pass encoding
</p></dd>
<dt> ‘<samp>-dct[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>DCT algorithm
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>auto</samp>’</dt>
<dd><p>autoselect a good one (default)
</p></dd>
<dt> ‘<samp>fastint</samp>’</dt>
<dd><p>fast integer
</p></dd>
<dt> ‘<samp>int</samp>’</dt>
<dd><p>accurate integer
</p></dd>
<dt> ‘<samp>mmx</samp>’</dt>
<dt> ‘<samp>altivec</samp>’</dt>
<dt> ‘<samp>faan</samp>’</dt>
<dd><p>floating point AAN DCT
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-lumi_mask[:stream_specifier] <var>float</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>compresses bright areas stronger than medium ones
</p></dd>
<dt> ‘<samp>-tcplx_mask[:stream_specifier] <var>float</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>temporal complexity masking
</p></dd>
<dt> ‘<samp>-scplx_mask[:stream_specifier] <var>float</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>spatial complexity masking
</p></dd>
<dt> ‘<samp>-p_mask[:stream_specifier] <var>float</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>inter masking
</p></dd>
<dt> ‘<samp>-dark_mask[:stream_specifier] <var>float</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>compresses dark areas stronger than medium ones
</p></dd>
<dt> ‘<samp>-idct[:stream_specifier] <var>integer</var> (<em>input/output,video</em>)</samp>’</dt>
<dd><p>select IDCT implementation
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>auto</samp>’</dt>
<dt> ‘<samp>int</samp>’</dt>
<dt> ‘<samp>simple</samp>’</dt>
<dt> ‘<samp>simplemmx</samp>’</dt>
<dt> ‘<samp>arm</samp>’</dt>
<dt> ‘<samp>altivec</samp>’</dt>
<dt> ‘<samp>sh4</samp>’</dt>
<dt> ‘<samp>simplearm</samp>’</dt>
<dt> ‘<samp>simplearmv5te</samp>’</dt>
<dt> ‘<samp>simplearmv6</samp>’</dt>
<dt> ‘<samp>simpleneon</samp>’</dt>
<dt> ‘<samp>simplealpha</samp>’</dt>
<dt> ‘<samp>ipp</samp>’</dt>
<dt> ‘<samp>xvid</samp>’</dt>
<dt> ‘<samp>xvidmmx</samp>’</dt>
<dt> ‘<samp>faani</samp>’</dt>
<dd><p>floating point AAN IDCT
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-ec[:stream_specifier] <var>flags</var> (<em>input,video</em>)</samp>’</dt>
<dd><p>set error concealment strategy
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>guess_mvs</samp>’</dt>
<dd><p>iterative motion vector (MV) search (slow)
</p></dd>
<dt> ‘<samp>deblock</samp>’</dt>
<dd><p>use strong deblock filter for damaged MBs
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-pred[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>prediction method
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>left</samp>’</dt>
<dt> ‘<samp>plane</samp>’</dt>
<dt> ‘<samp>median</samp>’</dt>
</dl>
</dd>
<dt> ‘<samp>-aspect[:stream_specifier] <var>rational number</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>sample aspect ratio
</p></dd>
<dt> ‘<samp>-debug[:stream_specifier] <var>flags</var> (<em>input/output,audio,video,subtitles</em>)</samp>’</dt>
<dd><p>print specific debug info
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>pict</samp>’</dt>
<dd><p>picture info
</p></dd>
<dt> ‘<samp>rc</samp>’</dt>
<dd><p>rate control
</p></dd>
<dt> ‘<samp>bitstream</samp>’</dt>
<dt> ‘<samp>mb_type</samp>’</dt>
<dd><p>macroblock (MB) type
</p></dd>
<dt> ‘<samp>qp</samp>’</dt>
<dd><p>per-block quantization parameter (QP)
</p></dd>
<dt> ‘<samp>mv</samp>’</dt>
<dd><p>motion vector
</p></dd>
<dt> ‘<samp>dct_coeff</samp>’</dt>
<dt> ‘<samp>skip</samp>’</dt>
<dt> ‘<samp>startcode</samp>’</dt>
<dt> ‘<samp>pts</samp>’</dt>
<dt> ‘<samp>er</samp>’</dt>
<dd><p>error recognition
</p></dd>
<dt> ‘<samp>mmco</samp>’</dt>
<dd><p>memory management control operations (H.264)
</p></dd>
<dt> ‘<samp>bugs</samp>’</dt>
<dt> ‘<samp>vis_qp</samp>’</dt>
<dd><p>visualize quantization parameter (QP), lower QP are tinted greener
</p></dd>
<dt> ‘<samp>vis_mb_type</samp>’</dt>
<dd><p>visualize block types
</p></dd>
<dt> ‘<samp>buffers</samp>’</dt>
<dd><p>picture buffer allocations
</p></dd>
<dt> ‘<samp>thread_ops</samp>’</dt>
<dd><p>threading operations
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-vismv[:stream_specifier] <var>integer</var> (<em>input,video</em>)</samp>’</dt>
<dd><p>visualize motion vectors (MVs)
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>pf</samp>’</dt>
<dd><p>forward predicted MVs of P-frames
</p></dd>
<dt> ‘<samp>bf</samp>’</dt>
<dd><p>forward predicted MVs of B-frames
</p></dd>
<dt> ‘<samp>bb</samp>’</dt>
<dd><p>backward predicted MVs of B-frames
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-cmp[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>full-pel ME compare function
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>sad</samp>’</dt>
<dd><p>sum of absolute differences, fast (default)
</p></dd>
<dt> ‘<samp>sse</samp>’</dt>
<dd><p>sum of squared errors
</p></dd>
<dt> ‘<samp>satd</samp>’</dt>
<dd><p>sum of absolute Hadamard transformed differences
</p></dd>
<dt> ‘<samp>dct</samp>’</dt>
<dd><p>sum of absolute DCT transformed differences
</p></dd>
<dt> ‘<samp>psnr</samp>’</dt>
<dd><p>sum of squared quantization errors (avoid, low quality)
</p></dd>
<dt> ‘<samp>bit</samp>’</dt>
<dd><p>number of bits needed for the block
</p></dd>
<dt> ‘<samp>rd</samp>’</dt>
<dd><p>rate distortion optimal, slow
</p></dd>
<dt> ‘<samp>zero</samp>’</dt>
<dd><p>0
</p></dd>
<dt> ‘<samp>vsad</samp>’</dt>
<dd><p>sum of absolute vertical differences
</p></dd>
<dt> ‘<samp>vsse</samp>’</dt>
<dd><p>sum of squared vertical differences
</p></dd>
<dt> ‘<samp>nsse</samp>’</dt>
<dd><p>noise preserving sum of squared differences
</p></dd>
<dt> ‘<samp>dctmax</samp>’</dt>
<dt> ‘<samp>chroma</samp>’</dt>
</dl>
</dd>
<dt> ‘<samp>-subcmp[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>sub-pel ME compare function
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>sad</samp>’</dt>
<dd><p>sum of absolute differences, fast (default)
</p></dd>
<dt> ‘<samp>sse</samp>’</dt>
<dd><p>sum of squared errors
</p></dd>
<dt> ‘<samp>satd</samp>’</dt>
<dd><p>sum of absolute Hadamard transformed differences
</p></dd>
<dt> ‘<samp>dct</samp>’</dt>
<dd><p>sum of absolute DCT transformed differences
</p></dd>
<dt> ‘<samp>psnr</samp>’</dt>
<dd><p>sum of squared quantization errors (avoid, low quality)
</p></dd>
<dt> ‘<samp>bit</samp>’</dt>
<dd><p>number of bits needed for the block
</p></dd>
<dt> ‘<samp>rd</samp>’</dt>
<dd><p>rate distortion optimal, slow
</p></dd>
<dt> ‘<samp>zero</samp>’</dt>
<dd><p>0
</p></dd>
<dt> ‘<samp>vsad</samp>’</dt>
<dd><p>sum of absolute vertical differences
</p></dd>
<dt> ‘<samp>vsse</samp>’</dt>
<dd><p>sum of squared vertical differences
</p></dd>
<dt> ‘<samp>nsse</samp>’</dt>
<dd><p>noise preserving sum of squared differences
</p></dd>
<dt> ‘<samp>dctmax</samp>’</dt>
<dt> ‘<samp>chroma</samp>’</dt>
</dl>
</dd>
<dt> ‘<samp>-mbcmp[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>macroblock compare function
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>sad</samp>’</dt>
<dd><p>sum of absolute differences, fast (default)
</p></dd>
<dt> ‘<samp>sse</samp>’</dt>
<dd><p>sum of squared errors
</p></dd>
<dt> ‘<samp>satd</samp>’</dt>
<dd><p>sum of absolute Hadamard transformed differences
</p></dd>
<dt> ‘<samp>dct</samp>’</dt>
<dd><p>sum of absolute DCT transformed differences
</p></dd>
<dt> ‘<samp>psnr</samp>’</dt>
<dd><p>sum of squared quantization errors (avoid, low quality)
</p></dd>
<dt> ‘<samp>bit</samp>’</dt>
<dd><p>number of bits needed for the block
</p></dd>
<dt> ‘<samp>rd</samp>’</dt>
<dd><p>rate distortion optimal, slow
</p></dd>
<dt> ‘<samp>zero</samp>’</dt>
<dd><p>0
</p></dd>
<dt> ‘<samp>vsad</samp>’</dt>
<dd><p>sum of absolute vertical differences
</p></dd>
<dt> ‘<samp>vsse</samp>’</dt>
<dd><p>sum of squared vertical differences
</p></dd>
<dt> ‘<samp>nsse</samp>’</dt>
<dd><p>noise preserving sum of squared differences
</p></dd>
<dt> ‘<samp>dctmax</samp>’</dt>
<dt> ‘<samp>chroma</samp>’</dt>
</dl>
</dd>
<dt> ‘<samp>-ildctcmp[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>interlaced DCT compare function
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>sad</samp>’</dt>
<dd><p>sum of absolute differences, fast (default)
</p></dd>
<dt> ‘<samp>sse</samp>’</dt>
<dd><p>sum of squared errors
</p></dd>
<dt> ‘<samp>satd</samp>’</dt>
<dd><p>sum of absolute Hadamard transformed differences
</p></dd>
<dt> ‘<samp>dct</samp>’</dt>
<dd><p>sum of absolute DCT transformed differences
</p></dd>
<dt> ‘<samp>psnr</samp>’</dt>
<dd><p>sum of squared quantization errors (avoid, low quality)
</p></dd>
<dt> ‘<samp>bit</samp>’</dt>
<dd><p>number of bits needed for the block
</p></dd>
<dt> ‘<samp>rd</samp>’</dt>
<dd><p>rate distortion optimal, slow
</p></dd>
<dt> ‘<samp>zero</samp>’</dt>
<dd><p>0
</p></dd>
<dt> ‘<samp>vsad</samp>’</dt>
<dd><p>sum of absolute vertical differences
</p></dd>
<dt> ‘<samp>vsse</samp>’</dt>
<dd><p>sum of squared vertical differences
</p></dd>
<dt> ‘<samp>nsse</samp>’</dt>
<dd><p>noise preserving sum of squared differences
</p></dd>
<dt> ‘<samp>dctmax</samp>’</dt>
<dt> ‘<samp>chroma</samp>’</dt>
</dl>
</dd>
<dt> ‘<samp>-dia_size[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>diamond type & size for motion estimation
</p></dd>
<dt> ‘<samp>-last_pred[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>amount of motion predictors from the previous frame
</p></dd>
<dt> ‘<samp>-preme[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>pre motion estimation
</p></dd>
<dt> ‘<samp>-precmp[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>pre motion estimation compare function
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>sad</samp>’</dt>
<dd><p>sum of absolute differences, fast (default)
</p></dd>
<dt> ‘<samp>sse</samp>’</dt>
<dd><p>sum of squared errors
</p></dd>
<dt> ‘<samp>satd</samp>’</dt>
<dd><p>sum of absolute Hadamard transformed differences
</p></dd>
<dt> ‘<samp>dct</samp>’</dt>
<dd><p>sum of absolute DCT transformed differences
</p></dd>
<dt> ‘<samp>psnr</samp>’</dt>
<dd><p>sum of squared quantization errors (avoid, low quality)
</p></dd>
<dt> ‘<samp>bit</samp>’</dt>
<dd><p>number of bits needed for the block
</p></dd>
<dt> ‘<samp>rd</samp>’</dt>
<dd><p>rate distortion optimal, slow
</p></dd>
<dt> ‘<samp>zero</samp>’</dt>
<dd><p>0
</p></dd>
<dt> ‘<samp>vsad</samp>’</dt>
<dd><p>sum of absolute vertical differences
</p></dd>
<dt> ‘<samp>vsse</samp>’</dt>
<dd><p>sum of squared vertical differences
</p></dd>
<dt> ‘<samp>nsse</samp>’</dt>
<dd><p>noise preserving sum of squared differences
</p></dd>
<dt> ‘<samp>dctmax</samp>’</dt>
<dt> ‘<samp>chroma</samp>’</dt>
</dl>
</dd>
<dt> ‘<samp>-pre_dia_size[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>diamond type & size for motion estimation pre-pass
</p></dd>
<dt> ‘<samp>-subq[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>sub-pel motion estimation quality
</p></dd>
<dt> ‘<samp>-me_range[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>limit motion vectors range (1023 for DivX player)
</p></dd>
<dt> ‘<samp>-ibias[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>intra quant bias
</p></dd>
<dt> ‘<samp>-pbias[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>inter quant bias
</p></dd>
<dt> ‘<samp>-global_quality[:stream_specifier] <var>integer</var> (<em>output,audio,video</em>)</samp>’</dt>
<dt> ‘<samp>-coder[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>vlc</samp>’</dt>
<dd><p>variable length coder / Huffman coder
</p></dd>
<dt> ‘<samp>ac</samp>’</dt>
<dd><p>arithmetic coder
</p></dd>
<dt> ‘<samp>raw</samp>’</dt>
<dd><p>raw (no encoding)
</p></dd>
<dt> ‘<samp>rle</samp>’</dt>
<dd><p>run-length coder
</p></dd>
<dt> ‘<samp>deflate</samp>’</dt>
<dd><p>deflate-based coder
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-context[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>context model
</p></dd>
<dt> ‘<samp>-mbd[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>macroblock decision algorithm (high quality mode)
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>simple</samp>’</dt>
<dd><p>use mbcmp (default)
</p></dd>
<dt> ‘<samp>bits</samp>’</dt>
<dd><p>use fewest bits
</p></dd>
<dt> ‘<samp>rd</samp>’</dt>
<dd><p>use best rate distortion
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-sc_threshold[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>scene change threshold
</p></dd>
<dt> ‘<samp>-lmin[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>minimum Lagrange factor (VBR)
</p></dd>
<dt> ‘<samp>-lmax[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>maximum Lagrange factor (VBR)
</p></dd>
<dt> ‘<samp>-nr[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>noise reduction
</p></dd>
<dt> ‘<samp>-rc_init_occupancy[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>number of bits which should be loaded into the rc buffer before decoding starts
</p></dd>
<dt> ‘<samp>-flags2[:stream_specifier] <var>flags</var> (<em>input/output,audio,video</em>)</samp>’</dt>
<dd>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>fast</samp>’</dt>
<dd><p>allow non-spec-compliant speedup tricks
</p></dd>
<dt> ‘<samp>noout</samp>’</dt>
<dd><p>skip bitstream encoding
</p></dd>
<dt> ‘<samp>ignorecrop</samp>’</dt>
<dd><p>ignore cropping information from sps
</p></dd>
<dt> ‘<samp>local_header</samp>’</dt>
<dd><p>place global headers at every keyframe instead of in extradata
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-error[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dt> ‘<samp>-threads[:stream_specifier] <var>integer</var> (<em>input/output,video</em>)</samp>’</dt>
<dd>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>auto</samp>’</dt>
<dd><p>autodetect a suitable number of threads to use
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-me_threshold[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>motion estimation threshold
</p></dd>
<dt> ‘<samp>-mb_threshold[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>macroblock threshold
</p></dd>
<dt> ‘<samp>-dc[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>intra_dc_precision
</p></dd>
<dt> ‘<samp>-nssew[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>nsse weight
</p></dd>
<dt> ‘<samp>-skip_top[:stream_specifier] <var>integer</var> (<em>input,video</em>)</samp>’</dt>
<dd><p>number of macroblock rows at the top which are skipped
</p></dd>
<dt> ‘<samp>-skip_bottom[:stream_specifier] <var>integer</var> (<em>input,video</em>)</samp>’</dt>
<dd><p>number of macroblock rows at the bottom which are skipped
</p></dd>
<dt> ‘<samp>-profile[:stream_specifier] <var>integer</var> (<em>output,audio,video</em>)</samp>’</dt>
<dd>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>unknown</samp>’</dt>
<dt> ‘<samp>aac_main</samp>’</dt>
<dt> ‘<samp>aac_low</samp>’</dt>
<dt> ‘<samp>aac_ssr</samp>’</dt>
<dt> ‘<samp>aac_ltp</samp>’</dt>
<dt> ‘<samp>aac_he</samp>’</dt>
<dt> ‘<samp>aac_he_v2</samp>’</dt>
<dt> ‘<samp>aac_ld</samp>’</dt>
<dt> ‘<samp>aac_eld</samp>’</dt>
<dt> ‘<samp>mpeg2_aac_low</samp>’</dt>
<dt> ‘<samp>mpeg2_aac_he</samp>’</dt>
<dt> ‘<samp>dts</samp>’</dt>
<dt> ‘<samp>dts_es</samp>’</dt>
<dt> ‘<samp>dts_96_24</samp>’</dt>
<dt> ‘<samp>dts_hd_hra</samp>’</dt>
<dt> ‘<samp>dts_hd_ma</samp>’</dt>
</dl>
</dd>
<dt> ‘<samp>-level[:stream_specifier] <var>integer</var> (<em>output,audio,video</em>)</samp>’</dt>
<dd>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>unknown</samp>’</dt>
</dl>
</dd>
<dt> ‘<samp>-skip_threshold[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>frame skip threshold
</p></dd>
<dt> ‘<samp>-skip_factor[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>frame skip factor
</p></dd>
<dt> ‘<samp>-skip_exp[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>frame skip exponent
</p></dd>
<dt> ‘<samp>-skipcmp[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>frame skip compare function
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>sad</samp>’</dt>
<dd><p>sum of absolute differences, fast (default)
</p></dd>
<dt> ‘<samp>sse</samp>’</dt>
<dd><p>sum of squared errors
</p></dd>
<dt> ‘<samp>satd</samp>’</dt>
<dd><p>sum of absolute Hadamard transformed differences
</p></dd>
<dt> ‘<samp>dct</samp>’</dt>
<dd><p>sum of absolute DCT transformed differences
</p></dd>
<dt> ‘<samp>psnr</samp>’</dt>
<dd><p>sum of squared quantization errors (avoid, low quality)
</p></dd>
<dt> ‘<samp>bit</samp>’</dt>
<dd><p>number of bits needed for the block
</p></dd>
<dt> ‘<samp>rd</samp>’</dt>
<dd><p>rate distortion optimal, slow
</p></dd>
<dt> ‘<samp>zero</samp>’</dt>
<dd><p>0
</p></dd>
<dt> ‘<samp>vsad</samp>’</dt>
<dd><p>sum of absolute vertical differences
</p></dd>
<dt> ‘<samp>vsse</samp>’</dt>
<dd><p>sum of squared vertical differences
</p></dd>
<dt> ‘<samp>nsse</samp>’</dt>
<dd><p>noise preserving sum of squared differences
</p></dd>
<dt> ‘<samp>dctmax</samp>’</dt>
<dt> ‘<samp>chroma</samp>’</dt>
</dl>
</dd>
<dt> ‘<samp>-border_mask[:stream_specifier] <var>float</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>increase the quantizer for macroblocks close to borders
</p></dd>
<dt> ‘<samp>-mblmin[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>minimum macroblock Lagrange factor (VBR)
</p></dd>
<dt> ‘<samp>-mblmax[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>maximum macroblock Lagrange factor (VBR)
</p></dd>
<dt> ‘<samp>-mepc[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>motion estimation bitrate penalty compensation (1.0 = 256)
</p></dd>
<dt> ‘<samp>-skip_loop_filter[:stream_specifier] <var>integer</var> (<em>input,video</em>)</samp>’</dt>
<dd>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>none</samp>’</dt>
<dt> ‘<samp>default</samp>’</dt>
<dt> ‘<samp>noref</samp>’</dt>
<dt> ‘<samp>bidir</samp>’</dt>
<dt> ‘<samp>nokey</samp>’</dt>
<dt> ‘<samp>all</samp>’</dt>
</dl>
</dd>
<dt> ‘<samp>-skip_idct[:stream_specifier] <var>integer</var> (<em>input,video</em>)</samp>’</dt>
<dd>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>none</samp>’</dt>
<dt> ‘<samp>default</samp>’</dt>
<dt> ‘<samp>noref</samp>’</dt>
<dt> ‘<samp>bidir</samp>’</dt>
<dt> ‘<samp>nokey</samp>’</dt>
<dt> ‘<samp>all</samp>’</dt>
</dl>
</dd>
<dt> ‘<samp>-skip_frame[:stream_specifier] <var>integer</var> (<em>input,video</em>)</samp>’</dt>
<dd>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>none</samp>’</dt>
<dt> ‘<samp>default</samp>’</dt>
<dt> ‘<samp>noref</samp>’</dt>
<dt> ‘<samp>bidir</samp>’</dt>
<dt> ‘<samp>nokey</samp>’</dt>
<dt> ‘<samp>all</samp>’</dt>
</dl>
</dd>
<dt> ‘<samp>-bidir_refine[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>refine the two motion vectors used in bidirectional macroblocks
</p></dd>
<dt> ‘<samp>-brd_scale[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>downscale frames for dynamic B-frame decision
</p></dd>
<dt> ‘<samp>-keyint_min[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>minimum interval between IDR-frames (x264)
</p></dd>
<dt> ‘<samp>-refs[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>reference frames to consider for motion compensation
</p></dd>
<dt> ‘<samp>-chromaoffset[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>chroma QP offset from luma
</p></dd>
<dt> ‘<samp>-trellis[:stream_specifier] <var>integer</var> (<em>output,audio,video</em>)</samp>’</dt>
<dd><p>rate-distortion optimal quantization
</p></dd>
<dt> ‘<samp>-sc_factor[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>multiplied by qscale for each frame and added to scene_change_score
</p></dd>
<dt> ‘<samp>-mv0_threshold[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dt> ‘<samp>-b_sensitivity[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>adjust sensitivity of b_frame_strategy 1
</p></dd>
<dt> ‘<samp>-compression_level[:stream_specifier] <var>integer</var> (<em>output,audio,video</em>)</samp>’</dt>
<dt> ‘<samp>-min_prediction_order[:stream_specifier] <var>integer</var> (<em>output,audio</em>)</samp>’</dt>
<dt> ‘<samp>-max_prediction_order[:stream_specifier] <var>integer</var> (<em>output,audio</em>)</samp>’</dt>
<dt> ‘<samp>-timecode_frame_start[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>GOP timecode frame start number, in non-drop-frame format
</p></dd>
<dt> ‘<samp>-request_channels[:stream_specifier] <var>integer</var> (<em>input,audio</em>)</samp>’</dt>
<dd><p>set desired number of audio channels
</p></dd>
<dt> ‘<samp>-channel_layout[:stream_specifier] <var>integer</var> (<em>input/output,audio</em>)</samp>’</dt>
<dd>
<p>Possible values:
</p></dd>
<dt> ‘<samp>-request_channel_layout[:stream_specifier] <var>integer</var> (<em>input,audio</em>)</samp>’</dt>
<dd>
<p>Possible values:
</p></dd>
<dt> ‘<samp>-rc_max_vbv_use[:stream_specifier] <var>float</var> (<em>output,video</em>)</samp>’</dt>
<dt> ‘<samp>-rc_min_vbv_use[:stream_specifier] <var>float</var> (<em>output,video</em>)</samp>’</dt>
<dt> ‘<samp>-ticks_per_frame[:stream_specifier] <var>integer</var> (<em>input/output,audio,video</em>)</samp>’</dt>
<dt> ‘<samp>-color_primaries[:stream_specifier] <var>integer</var> (<em>input/output,video</em>)</samp>’</dt>
<dd><p>color primaries
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>bt709</samp>’</dt>
<dd><p>BT.709
</p></dd>
<dt> ‘<samp>unspecified</samp>’</dt>
<dd><p>Unspecified
</p></dd>
<dt> ‘<samp>bt470m</samp>’</dt>
<dd><p>BT.470 M
</p></dd>
<dt> ‘<samp>bt470bg</samp>’</dt>
<dd><p>BT.470 BG
</p></dd>
<dt> ‘<samp>smpte170m</samp>’</dt>
<dd><p>SMPTE 170 M
</p></dd>
<dt> ‘<samp>smpte240m</samp>’</dt>
<dd><p>SMPTE 240 M
</p></dd>
<dt> ‘<samp>film</samp>’</dt>
<dd><p>Film
</p></dd>
<dt> ‘<samp>bt2020</samp>’</dt>
<dd><p>BT.2020
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-color_trc[:stream_specifier] <var>integer</var> (<em>input/output,video</em>)</samp>’</dt>
<dd><p>color transfert characteristic
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>bt709</samp>’</dt>
<dd><p>BT.709
</p></dd>
<dt> ‘<samp>unspecified</samp>’</dt>
<dd><p>Unspecified
</p></dd>
<dt> ‘<samp>gamma22</samp>’</dt>
<dd><p>Gamma 2.2
</p></dd>
<dt> ‘<samp>gamma28</samp>’</dt>
<dd><p>Gamma 2.8
</p></dd>
<dt> ‘<samp>smpte170m</samp>’</dt>
<dd><p>SMPTE 170 M
</p></dd>
<dt> ‘<samp>smpte240m</samp>’</dt>
<dd><p>SMPTE 240 M
</p></dd>
<dt> ‘<samp>linear</samp>’</dt>
<dd><p>Linear
</p></dd>
<dt> ‘<samp>log</samp>’</dt>
<dd><p>SMPTE 240 M
</p></dd>
<dt> ‘<samp>log_sqrt</samp>’</dt>
<dd><p>SMPTE 240 M
</p></dd>
<dt> ‘<samp>iec61966_2_4</samp>’</dt>
<dd><p>SMPTE 240 M
</p></dd>
<dt> ‘<samp>bt1361</samp>’</dt>
<dd><p>BT.1361
</p></dd>
<dt> ‘<samp>iec61966_2_1</samp>’</dt>
<dd><p>SMPTE 240 M
</p></dd>
<dt> ‘<samp>bt2020_10bit</samp>’</dt>
<dd><p>BT.2020 - 10 bit
</p></dd>
<dt> ‘<samp>bt2020_12bit</samp>’</dt>
<dd><p>BT.2020 - 12 bit
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-colorspace[:stream_specifier] <var>integer</var> (<em>input/output,video</em>)</samp>’</dt>
<dd><p>colorspace
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>rgb</samp>’</dt>
<dd><p>RGB
</p></dd>
<dt> ‘<samp>bt709</samp>’</dt>
<dd><p>BT.709
</p></dd>
<dt> ‘<samp>unspecified</samp>’</dt>
<dd><p>Unspecified
</p></dd>
<dt> ‘<samp>fcc</samp>’</dt>
<dd><p>FourCC
</p></dd>
<dt> ‘<samp>bt470bg</samp>’</dt>
<dd><p>BT.470 BG
</p></dd>
<dt> ‘<samp>smpte170m</samp>’</dt>
<dd><p>SMPTE 170 M
</p></dd>
<dt> ‘<samp>smpte240m</samp>’</dt>
<dd><p>SMPTE 240 M
</p></dd>
<dt> ‘<samp>ycocg</samp>’</dt>
<dd><p>YCOCG
</p></dd>
<dt> ‘<samp>bt2020_ncl</samp>’</dt>
<dd><p>BT.2020 NCL
</p></dd>
<dt> ‘<samp>bt2020_cl</samp>’</dt>
<dd><p>BT.2020 CL
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-color_range[:stream_specifier] <var>integer</var> (<em>input/output,video</em>)</samp>’</dt>
<dd><p>color range
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>unspecified</samp>’</dt>
<dd><p>Unspecified
</p></dd>
<dt> ‘<samp>mpeg</samp>’</dt>
<dd><p>MPEG (219*2^(n-8))
</p></dd>
<dt> ‘<samp>jpeg</samp>’</dt>
<dd><p>JPEG (2^n-1)
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-chroma_sample_location[:stream_specifier] <var>integer</var> (<em>input/output,video</em>)</samp>’</dt>
<dt> ‘<samp>-slices[:stream_specifier] <var>integer</var> (<em>output,video</em>)</samp>’</dt>
<dd><p>number of slices, used in parallelized encoding
</p></dd>
<dt> ‘<samp>-thread_type[:stream_specifier] <var>flags</var> (<em>input/output,video</em>)</samp>’</dt>
<dd><p>select multithreading type
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>slice</samp>’</dt>
<dt> ‘<samp>frame</samp>’</dt>
</dl>
</dd>
<dt> ‘<samp>-audio_service_type[:stream_specifier] <var>integer</var> (<em>output,audio</em>)</samp>’</dt>
<dd><p>audio service type
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>ma</samp>’</dt>
<dd><p>Main Audio Service
</p></dd>
<dt> ‘<samp>ef</samp>’</dt>
<dd><p>Effects
</p></dd>
<dt> ‘<samp>vi</samp>’</dt>
<dd><p>Visually Impaired
</p></dd>
<dt> ‘<samp>hi</samp>’</dt>
<dd><p>Hearing Impaired
</p></dd>
<dt> ‘<samp>di</samp>’</dt>
<dd><p>Dialogue
</p></dd>
<dt> ‘<samp>co</samp>’</dt>
<dd><p>Commentary
</p></dd>
<dt> ‘<samp>em</samp>’</dt>
<dd><p>Emergency
</p></dd>
<dt> ‘<samp>vo</samp>’</dt>
<dd><p>Voice Over
</p></dd>
<dt> ‘<samp>ka</samp>’</dt>
<dd><p>Karaoke
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-request_sample_fmt[:stream_specifier] <var>integer</var> (<em>input,audio</em>)</samp>’</dt>
<dd>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>u8</samp>’</dt>
<dd><p>8-bit unsigned integer
</p></dd>
<dt> ‘<samp>s16</samp>’</dt>
<dd><p>16-bit signed integer
</p></dd>
<dt> ‘<samp>s32</samp>’</dt>
<dd><p>32-bit signed integer
</p></dd>
<dt> ‘<samp>flt</samp>’</dt>
<dd><p>32-bit float
</p></dd>
<dt> ‘<samp>dbl</samp>’</dt>
<dd><p>64-bit double
</p></dd>
<dt> ‘<samp>u8p</samp>’</dt>
<dd><p>8-bit unsigned integer planar
</p></dd>
<dt> ‘<samp>s16p</samp>’</dt>
<dd><p>16-bit signed integer planar
</p></dd>
<dt> ‘<samp>s32p</samp>’</dt>
<dd><p>32-bit signed integer planar
</p></dd>
<dt> ‘<samp>fltp</samp>’</dt>
<dd><p>32-bit float planar
</p></dd>
<dt> ‘<samp>dblp</samp>’</dt>
<dd><p>64-bit double planar
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-refcounted_frames[:stream_specifier] <var>integer</var> (<em>input,audio,video</em>)</samp>’</dt>
<dt> ‘<samp>-side_data_only_packets[:stream_specifier] <var>integer</var> (<em>output,audio,video</em>)</samp>’</dt>
</dl>
<a name="Format-AVOptions"></a>
<h2 class="section"><a href="avconv.html#toc-Format-AVOptions">5.5 Format AVOptions</a></h2>
<dl compact="compact">
<dt> ‘<samp>-probesize <var>integer</var> (<em>input</em>)</samp>’</dt>
<dd><p>set probing size
</p></dd>
<dt> ‘<samp>-packetsize <var>integer</var> (<em>output</em>)</samp>’</dt>
<dd><p>set packet size
</p></dd>
<dt> ‘<samp>-fflags <var>flags</var> (<em>input/output</em>)</samp>’</dt>
<dd>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>flush_packets</samp>’</dt>
<dd><p>reduce the latency by flushing out packets immediately
</p></dd>
<dt> ‘<samp>ignidx</samp>’</dt>
<dd><p>ignore index
</p></dd>
<dt> ‘<samp>genpts</samp>’</dt>
<dd><p>generate pts
</p></dd>
<dt> ‘<samp>nofillin</samp>’</dt>
<dd><p>do not fill in missing values that can be exactly calculated
</p></dd>
<dt> ‘<samp>noparse</samp>’</dt>
<dd><p>disable AVParsers, this needs nofillin too
</p></dd>
<dt> ‘<samp>igndts</samp>’</dt>
<dd><p>ignore dts
</p></dd>
<dt> ‘<samp>discardcorrupt</samp>’</dt>
<dd><p>discard corrupted frames
</p></dd>
<dt> ‘<samp>nobuffer</samp>’</dt>
<dd><p>reduce the latency introduced by optional buffering
</p></dd>
<dt> ‘<samp>bitexact</samp>’</dt>
<dd><p>do not write random/volatile data
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-analyzeduration <var>integer</var> (<em>input</em>)</samp>’</dt>
<dd><p>how many microseconds are analyzed to estimate duration
</p></dd>
<dt> ‘<samp>-cryptokey <var>hexadecimal string</var> (<em>input</em>)</samp>’</dt>
<dd><p>decryption key
</p></dd>
<dt> ‘<samp>-indexmem <var>integer</var> (<em>input</em>)</samp>’</dt>
<dd><p>max memory used for timestamp index (per stream)
</p></dd>
<dt> ‘<samp>-rtbufsize <var>integer</var> (<em>input</em>)</samp>’</dt>
<dd><p>max memory used for buffering real-time frames
</p></dd>
<dt> ‘<samp>-fdebug <var>flags</var> (<em>input/output</em>)</samp>’</dt>
<dd><p>print specific debug info
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>ts</samp>’</dt>
</dl>
</dd>
<dt> ‘<samp>-max_delay <var>integer</var> (<em>input/output</em>)</samp>’</dt>
<dd><p>maximum muxing or demuxing delay in microseconds
</p></dd>
<dt> ‘<samp>-fpsprobesize <var>integer</var> (<em>input</em>)</samp>’</dt>
<dd><p>number of frames used to probe fps
</p></dd>
<dt> ‘<samp>-f_err_detect <var>flags</var> (<em>input</em>)</samp>’</dt>
<dd><p>set error detection flags (deprecated; use err_detect, save via avconv)
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>crccheck</samp>’</dt>
<dd><p>verify embedded CRCs
</p></dd>
<dt> ‘<samp>bitstream</samp>’</dt>
<dd><p>detect bitstream specification deviations
</p></dd>
<dt> ‘<samp>buffer</samp>’</dt>
<dd><p>detect improper bitstream length
</p></dd>
<dt> ‘<samp>explode</samp>’</dt>
<dd><p>abort decoding on minor error detection
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-err_detect <var>flags</var> (<em>input</em>)</samp>’</dt>
<dd><p>set error detection flags
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>crccheck</samp>’</dt>
<dd><p>verify embedded CRCs
</p></dd>
<dt> ‘<samp>bitstream</samp>’</dt>
<dd><p>detect bitstream specification deviations
</p></dd>
<dt> ‘<samp>buffer</samp>’</dt>
<dd><p>detect improper bitstream length
</p></dd>
<dt> ‘<samp>explode</samp>’</dt>
<dd><p>abort decoding on minor error detection
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-max_interleave_delta <var>integer</var> (<em>output</em>)</samp>’</dt>
<dd><p>maximum buffering duration for interleaving
</p></dd>
<dt> ‘<samp>-f_strict <var>integer</var> (<em>input/output</em>)</samp>’</dt>
<dd><p>how strictly to follow the standards (deprecated; use strict, save via avconv)
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>strict</samp>’</dt>
<dd><p>strictly conform to all the things in the spec no matter what the consequences
</p></dd>
<dt> ‘<samp>normal</samp>’</dt>
<dt> ‘<samp>experimental</samp>’</dt>
<dd><p>allow non-standardized experimental variants
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-strict <var>integer</var> (<em>input/output</em>)</samp>’</dt>
<dd><p>how strictly to follow the standards
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>strict</samp>’</dt>
<dd><p>strictly conform to all the things in the spec no matter what the consequences
</p></dd>
<dt> ‘<samp>normal</samp>’</dt>
<dt> ‘<samp>experimental</samp>’</dt>
<dd><p>allow non-standardized experimental variants
</p></dd>
</dl>
</dd>
</dl>
<a name="Main-options"></a>
<h2 class="section"><a href="avconv.html#toc-Main-options">5.6 Main options</a></h2>
<dl compact="compact">
<dt> ‘<samp>-f <var>fmt</var> (<em>input/output</em>)</samp>’</dt>
<dd><p>Force input or output file format. The format is normally autodetected for input
files and guessed from file extension for output files, so this option is not
needed in most cases.
</p>
</dd>
<dt> ‘<samp>-i <var>filename</var> (<em>input</em>)</samp>’</dt>
<dd><p>input file name
</p>
</dd>
<dt> ‘<samp>-y (<em>global</em>)</samp>’</dt>
<dd><p>Overwrite output files without asking.
</p>
</dd>
<dt> ‘<samp>-n (<em>global</em>)</samp>’</dt>
<dd><p>Immediately exit when output files already exist.
</p>
</dd>
<dt> ‘<samp>-c[:<var>stream_specifier</var>] <var>codec</var> (<em>input/output,per-stream</em>)</samp>’</dt>
<dt> ‘<samp>-codec[:<var>stream_specifier</var>] <var>codec</var> (<em>input/output,per-stream</em>)</samp>’</dt>
<dd><p>Select an encoder (when used before an output file) or a decoder (when used
before an input file) for one or more streams. <var>codec</var> is the name of a
decoder/encoder or a special value <code>copy</code> (output only) to indicate that
the stream is not to be reencoded.
</p>
<p>For example
</p><table><tr><td> </td><td><pre class="example">avconv -i INPUT -map 0 -c:v libx264 -c:a copy OUTPUT
</pre></td></tr></table>
<p>encodes all video streams with libx264 and copies all audio streams.
</p>
<p>For each stream, the last matching <code>c</code> option is applied, so
</p><table><tr><td> </td><td><pre class="example">avconv -i INPUT -map 0 -c copy -c:v:1 libx264 -c:a:137 libvorbis OUTPUT
</pre></td></tr></table>
<p>will copy all the streams except the second video, which will be encoded with
libx264, and the 138th audio, which will be encoded with libvorbis.
</p>
</dd>
<dt> ‘<samp>-t <var>duration</var> (<em>output</em>)</samp>’</dt>
<dd><p>Stop writing the output after its duration reaches <var>duration</var>.
<var>duration</var> may be a number in seconds, or in <code>hh:mm:ss[.xxx]</code> form.
</p>
</dd>
<dt> ‘<samp>-fs <var>limit_size</var> (<em>output</em>)</samp>’</dt>
<dd><p>Set the file size limit.
</p>
</dd>
<dt> ‘<samp>-ss <var>position</var> (<em>input/output</em>)</samp>’</dt>
<dd><p>When used as an input option (before <code>-i</code>), seeks in this input file to
<var>position</var>. Note the in most formats it is not possible to seek exactly, so
<code>avconv</code> will seek to the closest seek point before <var>position</var>.
When transcoding and ‘<samp>-accurate_seek</samp>’ is enabled (the default), this
extra segment between the seek point and <var>position</var> will be decoded and
discarded. When doing stream copy or when ‘<samp>-noaccurate_seek</samp>’ is used, it
will be preserved.
</p>
<p>When used as an output option (before an output filename), decodes but discards
input until the timestamps reach <var>position</var>.
</p>
<p><var>position</var> may be either in seconds or in <code>hh:mm:ss[.xxx]</code> form.
</p>
</dd>
<dt> ‘<samp>-itsoffset <var>offset</var> (<em>input</em>)</samp>’</dt>
<dd><p>Set the input time offset in seconds.
<code>[-]hh:mm:ss[.xxx]</code> syntax is also supported.
The offset is added to the timestamps of the input files.
Specifying a positive offset means that the corresponding
streams are delayed by <var>offset</var> seconds.
</p>
</dd>
<dt> ‘<samp>-metadata[:metadata_specifier] <var>key</var>=<var>value</var> (<em>output,per-metadata</em>)</samp>’</dt>
<dd><p>Set a metadata key/value pair.
</p>
<p>An optional <var>metadata_specifier</var> may be given to set metadata
on streams or chapters. See <code>-map_metadata</code> documentation for
details.
</p>
<p>This option overrides metadata set with <code>-map_metadata</code>. It is
also possible to delete metadata by using an empty value.
</p>
<p>For example, for setting the title in the output file:
</p><table><tr><td> </td><td><pre class="example">avconv -i in.avi -metadata title="my title" out.flv
</pre></td></tr></table>
<p>To set the language of the first audio stream:
</p><table><tr><td> </td><td><pre class="example">avconv -i INPUT -metadata:s:a:0 language=eng OUTPUT
</pre></td></tr></table>
</dd>
<dt> ‘<samp>-target <var>type</var> (<em>output</em>)</samp>’</dt>
<dd><p>Specify target file type (<code>vcd</code>, <code>svcd</code>, <code>dvd</code>, <code>dv</code>,
<code>dv50</code>). <var>type</var> may be prefixed with <code>pal-</code>, <code>ntsc-</code> or
<code>film-</code> to use the corresponding standard. All the format options
(bitrate, codecs, buffer sizes) are then set automatically. You can just type:
</p>
<table><tr><td> </td><td><pre class="example">avconv -i myfile.avi -target vcd /tmp/vcd.mpg
</pre></td></tr></table>
<p>Nevertheless you can specify additional options as long as you know
they do not conflict with the standard, as in:
</p>
<table><tr><td> </td><td><pre class="example">avconv -i myfile.avi -target vcd -bf 2 /tmp/vcd.mpg
</pre></td></tr></table>
</dd>
<dt> ‘<samp>-dframes <var>number</var> (<em>output</em>)</samp>’</dt>
<dd><p>Set the number of data frames to record. This is an alias for <code>-frames:d</code>.
</p>
</dd>
<dt> ‘<samp>-frames[:<var>stream_specifier</var>] <var>framecount</var> (<em>output,per-stream</em>)</samp>’</dt>
<dd><p>Stop writing to the stream after <var>framecount</var> frames.
</p>
</dd>
<dt> ‘<samp>-q[:<var>stream_specifier</var>] <var>q</var> (<em>output,per-stream</em>)</samp>’</dt>
<dt> ‘<samp>-qscale[:<var>stream_specifier</var>] <var>q</var> (<em>output,per-stream</em>)</samp>’</dt>
<dd><p>Use fixed quality scale (VBR). The meaning of <var>q</var> is
codec-dependent.
</p>
</dd>
<dt> ‘<samp>-filter[:<var>stream_specifier</var>] <var>filter_graph</var> (<em>output,per-stream</em>)</samp>’</dt>
<dd><p><var>filter_graph</var> is a description of the filter graph to apply to
the stream. Use <code>-filters</code> to show all the available filters
(including also sources and sinks).
</p>
<p>See also the ‘<samp>-filter_complex</samp>’ option if you want to create filter graphs
with multiple inputs and/or outputs.
</p>
</dd>
<dt> ‘<samp>-filter_script[:<var>stream_specifier</var>] <var>filename</var> (<em>output,per-stream</em>)</samp>’</dt>
<dd><p>This option is similar to ‘<samp>-filter</samp>’, the only difference is that its
argument is the name of the file from which a filtergraph description is to be
read.
</p>
</dd>
<dt> ‘<samp>-pre[:<var>stream_specifier</var>] <var>preset_name</var> (<em>output,per-stream</em>)</samp>’</dt>
<dd><p>Specify the preset for matching stream(s).
</p>
</dd>
<dt> ‘<samp>-stats (<em>global</em>)</samp>’</dt>
<dd><p>Print encoding progress/statistics. On by default.
</p>
</dd>
<dt> ‘<samp>-attach <var>filename</var> (<em>output</em>)</samp>’</dt>
<dd><p>Add an attachment to the output file. This is supported by a few formats
like Matroska for e.g. fonts used in rendering subtitles. Attachments
are implemented as a specific type of stream, so this option will add
a new stream to the file. It is then possible to use per-stream options
on this stream in the usual way. Attachment streams created with this
option will be created after all the other streams (i.e. those created
with <code>-map</code> or automatic mappings).
</p>
<p>Note that for Matroska you also have to set the mimetype metadata tag:
</p><table><tr><td> </td><td><pre class="example">avconv -i INPUT -attach DejaVuSans.ttf -metadata:s:2 mimetype=application/x-truetype-font out.mkv
</pre></td></tr></table>
<p>(assuming that the attachment stream will be third in the output file).
</p>
</dd>
<dt> ‘<samp>-dump_attachment[:<var>stream_specifier</var>] <var>filename</var> (<em>input,per-stream</em>)</samp>’</dt>
<dd><p>Extract the matching attachment stream into a file named <var>filename</var>. If
<var>filename</var> is empty, then the value of the <code>filename</code> metadata tag
will be used.
</p>
<p>E.g. to extract the first attachment to a file named ’out.ttf’:
</p><table><tr><td> </td><td><pre class="example">avconv -dump_attachment:t:0 out.ttf INPUT
</pre></td></tr></table>
<p>To extract all attachments to files determined by the <code>filename</code> tag:
</p><table><tr><td> </td><td><pre class="example">avconv -dump_attachment:t "" INPUT
</pre></td></tr></table>
<p>Technical note – attachments are implemented as codec extradata, so this
option can actually be used to extract extradata from any stream, not just
attachments.
</p>
</dd>
</dl>
<a name="Video-Options"></a>
<h2 class="section"><a href="avconv.html#toc-Video-Options">5.7 Video Options</a></h2>
<dl compact="compact">
<dt> ‘<samp>-vframes <var>number</var> (<em>output</em>)</samp>’</dt>
<dd><p>Set the number of video frames to record. This is an alias for <code>-frames:v</code>.
</p></dd>
<dt> ‘<samp>-r[:<var>stream_specifier</var>] <var>fps</var> (<em>input/output,per-stream</em>)</samp>’</dt>
<dd><p>Set frame rate (Hz value, fraction or abbreviation).
</p>
<p>As an input option, ignore any timestamps stored in the file and instead
generate timestamps assuming constant frame rate <var>fps</var>.
</p>
<p>As an output option, duplicate or drop input frames to achieve constant output
frame rate <var>fps</var> (note that this actually causes the <code>fps</code> filter to be
inserted to the end of the corresponding filtergraph).
</p>
</dd>
<dt> ‘<samp>-s[:<var>stream_specifier</var>] <var>size</var> (<em>input/output,per-stream</em>)</samp>’</dt>
<dd><p>Set frame size.
</p>
<p>As an input option, this is a shortcut for the ‘<samp>video_size</samp>’ private
option, recognized by some demuxers for which the frame size is either not
stored in the file or is configurable – e.g. raw video or video grabbers.
</p>
<p>As an output option, this inserts the <code>scale</code> video filter to the
<em>end</em> of the corresponding filtergraph. Please use the <code>scale</code> filter
directly to insert it at the beginning or some other place.
</p>
<p>The format is ‘<samp>wxh</samp>’ (default - same as source). The following
abbreviations are recognized:
</p><dl compact="compact">
<dt> ‘<samp>sqcif</samp>’</dt>
<dd><p>128x96
</p></dd>
<dt> ‘<samp>qcif</samp>’</dt>
<dd><p>176x144
</p></dd>
<dt> ‘<samp>cif</samp>’</dt>
<dd><p>352x288
</p></dd>
<dt> ‘<samp>4cif</samp>’</dt>
<dd><p>704x576
</p></dd>
<dt> ‘<samp>16cif</samp>’</dt>
<dd><p>1408x1152
</p></dd>
<dt> ‘<samp>qqvga</samp>’</dt>
<dd><p>160x120
</p></dd>
<dt> ‘<samp>qvga</samp>’</dt>
<dd><p>320x240
</p></dd>
<dt> ‘<samp>vga</samp>’</dt>
<dd><p>640x480
</p></dd>
<dt> ‘<samp>svga</samp>’</dt>
<dd><p>800x600
</p></dd>
<dt> ‘<samp>xga</samp>’</dt>
<dd><p>1024x768
</p></dd>
<dt> ‘<samp>uxga</samp>’</dt>
<dd><p>1600x1200
</p></dd>
<dt> ‘<samp>qxga</samp>’</dt>
<dd><p>2048x1536
</p></dd>
<dt> ‘<samp>sxga</samp>’</dt>
<dd><p>1280x1024
</p></dd>
<dt> ‘<samp>qsxga</samp>’</dt>
<dd><p>2560x2048
</p></dd>
<dt> ‘<samp>hsxga</samp>’</dt>
<dd><p>5120x4096
</p></dd>
<dt> ‘<samp>wvga</samp>’</dt>
<dd><p>852x480
</p></dd>
<dt> ‘<samp>wxga</samp>’</dt>
<dd><p>1366x768
</p></dd>
<dt> ‘<samp>wsxga</samp>’</dt>
<dd><p>1600x1024
</p></dd>
<dt> ‘<samp>wuxga</samp>’</dt>
<dd><p>1920x1200
</p></dd>
<dt> ‘<samp>woxga</samp>’</dt>
<dd><p>2560x1600
</p></dd>
<dt> ‘<samp>wqsxga</samp>’</dt>
<dd><p>3200x2048
</p></dd>
<dt> ‘<samp>wquxga</samp>’</dt>
<dd><p>3840x2400
</p></dd>
<dt> ‘<samp>whsxga</samp>’</dt>
<dd><p>6400x4096
</p></dd>
<dt> ‘<samp>whuxga</samp>’</dt>
<dd><p>7680x4800
</p></dd>
<dt> ‘<samp>cga</samp>’</dt>
<dd><p>320x200
</p></dd>
<dt> ‘<samp>ega</samp>’</dt>
<dd><p>640x350
</p></dd>
<dt> ‘<samp>hd480</samp>’</dt>
<dd><p>852x480
</p></dd>
<dt> ‘<samp>hd720</samp>’</dt>
<dd><p>1280x720
</p></dd>
<dt> ‘<samp>hd1080</samp>’</dt>
<dd><p>1920x1080
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-aspect[:<var>stream_specifier</var>] <var>aspect</var> (<em>output,per-stream</em>)</samp>’</dt>
<dd><p>Set the video display aspect ratio specified by <var>aspect</var>.
</p>
<p><var>aspect</var> can be a floating point number string, or a string of the
form <var>num</var>:<var>den</var>, where <var>num</var> and <var>den</var> are the
numerator and denominator of the aspect ratio. For example "4:3",
"16:9", "1.3333", and "1.7777" are valid argument values.
</p>
</dd>
<dt> ‘<samp>-vn (<em>output</em>)</samp>’</dt>
<dd><p>Disable video recording.
</p>
</dd>
<dt> ‘<samp>-vcodec <var>codec</var> (<em>output</em>)</samp>’</dt>
<dd><p>Set the video codec. This is an alias for <code>-codec:v</code>.
</p>
</dd>
<dt> ‘<samp>-pass[:<var>stream_specifier</var>] <var>n</var> (<em>output,per-stream</em>)</samp>’</dt>
<dd><p>Select the pass number (1 or 2). It is used to do two-pass
video encoding. The statistics of the video are recorded in the first
pass into a log file (see also the option -passlogfile),
and in the second pass that log file is used to generate the video
at the exact requested bitrate.
On pass 1, you may just deactivate audio and set output to null,
examples for Windows and Unix:
</p><table><tr><td> </td><td><pre class="example">avconv -i foo.mov -c:v libxvid -pass 1 -an -f rawvideo -y NUL
avconv -i foo.mov -c:v libxvid -pass 1 -an -f rawvideo -y /dev/null
</pre></td></tr></table>
</dd>
<dt> ‘<samp>-passlogfile[:<var>stream_specifier</var>] <var>prefix</var> (<em>output,per-stream</em>)</samp>’</dt>
<dd><p>Set two-pass log file name prefix to <var>prefix</var>, the default file name
prefix is “av2pass”. The complete file name will be
‘<tt>PREFIX-N.log</tt>’, where N is a number specific to the output
stream.
</p>
</dd>
<dt> ‘<samp>-vf <var>filter_graph</var> (<em>output</em>)</samp>’</dt>
<dd><p><var>filter_graph</var> is a description of the filter graph to apply to
the input video.
Use the option "-filters" to show all the available filters (including
also sources and sinks). This is an alias for <code>-filter:v</code>.
</p>
</dd>
</dl>
<a name="Advanced-Video-Options"></a>
<h2 class="section"><a href="avconv.html#toc-Advanced-Video-Options">5.8 Advanced Video Options</a></h2>
<dl compact="compact">
<dt> ‘<samp>-pix_fmt[:<var>stream_specifier</var>] <var>format</var> (<em>input/output,per-stream</em>)</samp>’</dt>
<dd><p>Set pixel format. Use <code>-pix_fmts</code> to show all the supported
pixel formats.
</p></dd>
<dt> ‘<samp>-sws_flags <var>flags</var> (<em>input/output</em>)</samp>’</dt>
<dd><p>Set SwScaler flags.
</p></dd>
<dt> ‘<samp>-vdt <var>n</var></samp>’</dt>
<dd><p>Discard threshold.
</p>
</dd>
<dt> ‘<samp>-rc_override[:<var>stream_specifier</var>] <var>override</var> (<em>output,per-stream</em>)</samp>’</dt>
<dd><p>rate control override for specific intervals
</p>
</dd>
<dt> ‘<samp>-vstats</samp>’</dt>
<dd><p>Dump video coding statistics to ‘<tt>vstats_HHMMSS.log</tt>’.
</p></dd>
<dt> ‘<samp>-vstats_file <var>file</var></samp>’</dt>
<dd><p>Dump video coding statistics to <var>file</var>.
</p></dd>
<dt> ‘<samp>-top[:<var>stream_specifier</var>] <var>n</var> (<em>output,per-stream</em>)</samp>’</dt>
<dd><p>top=1/bottom=0/auto=-1 field first
</p></dd>
<dt> ‘<samp>-dc <var>precision</var></samp>’</dt>
<dd><p>Intra_dc_precision.
</p></dd>
<dt> ‘<samp>-vtag <var>fourcc/tag</var> (<em>output</em>)</samp>’</dt>
<dd><p>Force video tag/fourcc. This is an alias for <code>-tag:v</code>.
</p></dd>
<dt> ‘<samp>-qphist (<em>global</em>)</samp>’</dt>
<dd><p>Show QP histogram.
</p></dd>
<dt> ‘<samp>-force_key_frames[:<var>stream_specifier</var>] <var>time</var>[,<var>time</var>...] (<em>output,per-stream</em>)</samp>’</dt>
<dd><p>Force key frames at the specified timestamps, more precisely at the first
frames after each specified time.
This option can be useful to ensure that a seek point is present at a
chapter mark or any other designated place in the output file.
The timestamps must be specified in ascending order.
</p>
</dd>
<dt> ‘<samp>-copyinkf[:<var>stream_specifier</var>] (<em>output,per-stream</em>)</samp>’</dt>
<dd><p>When doing stream copy, copy also non-key frames found at the
beginning.
</p>
</dd>
<dt> ‘<samp>-hwaccel[:<var>stream_specifier</var>] <var>hwaccel</var> (<em>input,per-stream</em>)</samp>’</dt>
<dd><p>Use hardware acceleration to decode the matching stream(s). The allowed values
of <var>hwaccel</var> are:
</p><dl compact="compact">
<dt> ‘<samp>none</samp>’</dt>
<dd><p>Do not use any hardware acceleration (the default).
</p>
</dd>
<dt> ‘<samp>auto</samp>’</dt>
<dd><p>Automatically select the hardware acceleration method.
</p>
</dd>
<dt> ‘<samp>vda</samp>’</dt>
<dd><p>Use Apple VDA hardware acceleration.
</p>
</dd>
<dt> ‘<samp>vdpau</samp>’</dt>
<dd><p>Use VDPAU (Video Decode and Presentation API for Unix) hardware acceleration.
</p>
</dd>
<dt> ‘<samp>dxva2</samp>’</dt>
<dd><p>Use DXVA2 (DirectX Video Acceleration) hardware acceleration.
</p></dd>
</dl>
<p>This option has no effect if the selected hwaccel is not available or not
supported by the chosen decoder.
</p>
<p>Note that most acceleration methods are intended for playback and will not be
faster than software decoding on modern CPUs. Additionally, <code>avconv</code>
will usually need to copy the decoded frames from the GPU memory into the system
memory, resulting in further performance loss. This option is thus mainly
useful for testing.
</p>
</dd>
<dt> ‘<samp>-hwaccel_device[:<var>stream_specifier</var>] <var>hwaccel_device</var> (<em>input,per-stream</em>)</samp>’</dt>
<dd><p>Select a device to use for hardware acceleration.
</p>
<p>This option only makes sense when the ‘<samp>-hwaccel</samp>’ option is also
specified. Its exact meaning depends on the specific hardware acceleration
method chosen.
</p>
<dl compact="compact">
<dt> ‘<samp>vdpau</samp>’</dt>
<dd><p>For VDPAU, this option specifies the X11 display/screen to use. If this option
is not specified, the value of the <var>DISPLAY</var> environment variable is used
</p>
</dd>
<dt> ‘<samp>dxva2</samp>’</dt>
<dd><p>For DXVA2, this option should contain the number of the display adapter to use.
If this option is not specified, the default adapter is used.
</p></dd>
</dl>
</dd>
</dl>
<a name="Audio-Options"></a>
<h2 class="section"><a href="avconv.html#toc-Audio-Options">5.9 Audio Options</a></h2>
<dl compact="compact">
<dt> ‘<samp>-aframes <var>number</var> (<em>output</em>)</samp>’</dt>
<dd><p>Set the number of audio frames to record. This is an alias for <code>-frames:a</code>.
</p></dd>
<dt> ‘<samp>-ar[:<var>stream_specifier</var>] <var>freq</var> (<em>input/output,per-stream</em>)</samp>’</dt>
<dd><p>Set the audio sampling frequency. For output streams it is set by
default to the frequency of the corresponding input stream. For input
streams this option only makes sense for audio grabbing devices and raw
demuxers and is mapped to the corresponding demuxer options.
</p></dd>
<dt> ‘<samp>-aq <var>q</var> (<em>output</em>)</samp>’</dt>
<dd><p>Set the audio quality (codec-specific, VBR). This is an alias for -q:a.
</p></dd>
<dt> ‘<samp>-ac[:<var>stream_specifier</var>] <var>channels</var> (<em>input/output,per-stream</em>)</samp>’</dt>
<dd><p>Set the number of audio channels. For output streams it is set by
default to the number of input audio channels. For input streams
this option only makes sense for audio grabbing devices and raw demuxers
and is mapped to the corresponding demuxer options.
</p></dd>
<dt> ‘<samp>-an (<em>output</em>)</samp>’</dt>
<dd><p>Disable audio recording.
</p></dd>
<dt> ‘<samp>-acodec <var>codec</var> (<em>input/output</em>)</samp>’</dt>
<dd><p>Set the audio codec. This is an alias for <code>-codec:a</code>.
</p></dd>
<dt> ‘<samp>-sample_fmt[:<var>stream_specifier</var>] <var>sample_fmt</var> (<em>output,per-stream</em>)</samp>’</dt>
<dd><p>Set the audio sample format. Use <code>-sample_fmts</code> to get a list
of supported sample formats.
</p></dd>
<dt> ‘<samp>-af <var>filter_graph</var> (<em>output</em>)</samp>’</dt>
<dd><p><var>filter_graph</var> is a description of the filter graph to apply to
the input audio.
Use the option "-filters" to show all the available filters (including
also sources and sinks). This is an alias for <code>-filter:a</code>.
</p></dd>
</dl>
<a name="Advanced-Audio-options_003a"></a>
<h2 class="section"><a href="avconv.html#toc-Advanced-Audio-options_003a">5.10 Advanced Audio options:</a></h2>
<dl compact="compact">
<dt> ‘<samp>-atag <var>fourcc/tag</var> (<em>output</em>)</samp>’</dt>
<dd><p>Force audio tag/fourcc. This is an alias for <code>-tag:a</code>.
</p></dd>
</dl>
<a name="Subtitle-options_003a"></a>
<h2 class="section"><a href="avconv.html#toc-Subtitle-options_003a">5.11 Subtitle options:</a></h2>
<dl compact="compact">
<dt> ‘<samp>-scodec <var>codec</var> (<em>input/output</em>)</samp>’</dt>
<dd><p>Set the subtitle codec. This is an alias for <code>-codec:s</code>.
</p></dd>
<dt> ‘<samp>-sn (<em>output</em>)</samp>’</dt>
<dd><p>Disable subtitle recording.
</p></dd>
</dl>
<a name="Advanced-options"></a>
<h2 class="section"><a href="avconv.html#toc-Advanced-options">5.12 Advanced options</a></h2>
<dl compact="compact">
<dt> ‘<samp>-map [-]<var>input_file_id</var>[:<var>stream_specifier</var>][,<var>sync_file_id</var>[:<var>stream_specifier</var>]] | <var>[linklabel]</var> (<em>output</em>)</samp>’</dt>
<dd>
<p>Designate one or more input streams as a source for the output file. Each input
stream is identified by the input file index <var>input_file_id</var> and
the input stream index <var>input_stream_id</var> within the input
file. Both indices start at 0. If specified,
<var>sync_file_id</var>:<var>stream_specifier</var> sets which input stream
is used as a presentation sync reference.
</p>
<p>The first <code>-map</code> option on the command line specifies the
source for output stream 0, the second <code>-map</code> option specifies
the source for output stream 1, etc.
</p>
<p>A <code>-</code> character before the stream identifier creates a "negative" mapping.
It disables matching streams from already created mappings.
</p>
<p>An alternative <var>[linklabel]</var> form will map outputs from complex filter
graphs (see the ‘<samp>-filter_complex</samp>’ option) to the output file.
<var>linklabel</var> must correspond to a defined output link label in the graph.
</p>
<p>For example, to map ALL streams from the first input file to output
</p><table><tr><td> </td><td><pre class="example">avconv -i INPUT -map 0 output
</pre></td></tr></table>
<p>For example, if you have two audio streams in the first input file,
these streams are identified by "0:0" and "0:1". You can use
<code>-map</code> to select which streams to place in an output file. For
example:
</p><table><tr><td> </td><td><pre class="example">avconv -i INPUT -map 0:1 out.wav
</pre></td></tr></table>
<p>will map the input stream in ‘<tt>INPUT</tt>’ identified by "0:1" to
the (single) output stream in ‘<tt>out.wav</tt>’.
</p>
<p>For example, to select the stream with index 2 from input file
‘<tt>a.mov</tt>’ (specified by the identifier "0:2"), and stream with
index 6 from input ‘<tt>b.mov</tt>’ (specified by the identifier "1:6"),
and copy them to the output file ‘<tt>out.mov</tt>’:
</p><table><tr><td> </td><td><pre class="example">avconv -i a.mov -i b.mov -c copy -map 0:2 -map 1:6 out.mov
</pre></td></tr></table>
<p>To select all video and the third audio stream from an input file:
</p><table><tr><td> </td><td><pre class="example">avconv -i INPUT -map 0:v -map 0:a:2 OUTPUT
</pre></td></tr></table>
<p>To map all the streams except the second audio, use negative mappings
</p><table><tr><td> </td><td><pre class="example">avconv -i INPUT -map 0 -map -0:a:1 OUTPUT
</pre></td></tr></table>
<p>To pick the English audio stream:
</p><table><tr><td> </td><td><pre class="example">avconv -i INPUT -map 0:m:language:eng OUTPUT
</pre></td></tr></table>
<p>Note that using this option disables the default mappings for this output file.
</p>
</dd>
<dt> ‘<samp>-map_metadata[:<var>metadata_spec_out</var>] <var>infile</var>[:<var>metadata_spec_in</var>] (<em>output,per-metadata</em>)</samp>’</dt>
<dd><p>Set metadata information of the next output file from <var>infile</var>. Note that
those are file indices (zero-based), not filenames.
Optional <var>metadata_spec_in/out</var> parameters specify, which metadata to copy.
A metadata specifier can have the following forms:
</p><dl compact="compact">
<dt> ‘<samp><var>g</var></samp>’</dt>
<dd><p>global metadata, i.e. metadata that applies to the whole file
</p>
</dd>
<dt> ‘<samp><var>s</var>[:<var>stream_spec</var>]</samp>’</dt>
<dd><p>per-stream metadata. <var>stream_spec</var> is a stream specifier as described
in the <a href="#Stream-specifiers">Stream specifiers</a> chapter. In an input metadata specifier, the first
matching stream is copied from. In an output metadata specifier, all matching
streams are copied to.
</p>
</dd>
<dt> ‘<samp><var>c</var>:<var>chapter_index</var></samp>’</dt>
<dd><p>per-chapter metadata. <var>chapter_index</var> is the zero-based chapter index.
</p>
</dd>
<dt> ‘<samp><var>p</var>:<var>program_index</var></samp>’</dt>
<dd><p>per-program metadata. <var>program_index</var> is the zero-based program index.
</p></dd>
</dl>
<p>If metadata specifier is omitted, it defaults to global.
</p>
<p>By default, global metadata is copied from the first input file,
per-stream and per-chapter metadata is copied along with streams/chapters. These
default mappings are disabled by creating any mapping of the relevant type. A negative
file index can be used to create a dummy mapping that just disables automatic copying.
</p>
<p>For example to copy metadata from the first stream of the input file to global metadata
of the output file:
</p><table><tr><td> </td><td><pre class="example">avconv -i in.ogg -map_metadata 0:s:0 out.mp3
</pre></td></tr></table>
<p>To do the reverse, i.e. copy global metadata to all audio streams:
</p><table><tr><td> </td><td><pre class="example">avconv -i in.mkv -map_metadata:s:a 0:g out.mkv
</pre></td></tr></table>
<p>Note that simple <code>0</code> would work as well in this example, since global
metadata is assumed by default.
</p>
</dd>
<dt> ‘<samp>-map_chapters <var>input_file_index</var> (<em>output</em>)</samp>’</dt>
<dd><p>Copy chapters from input file with index <var>input_file_index</var> to the next
output file. If no chapter mapping is specified, then chapters are copied from
the first input file with at least one chapter. Use a negative file index to
disable any chapter copying.
</p></dd>
<dt> ‘<samp>-debug</samp>’</dt>
<dd><p>Print specific debug info.
</p></dd>
<dt> ‘<samp>-benchmark (<em>global</em>)</samp>’</dt>
<dd><p>Show benchmarking information at the end of an encode.
Shows CPU time used and maximum memory consumption.
Maximum memory consumption is not supported on all systems,
it will usually display as 0 if not supported.
</p></dd>
<dt> ‘<samp>-timelimit <var>duration</var> (<em>global</em>)</samp>’</dt>
<dd><p>Exit after avconv has been running for <var>duration</var> seconds.
</p></dd>
<dt> ‘<samp>-dump (<em>global</em>)</samp>’</dt>
<dd><p>Dump each input packet to stderr.
</p></dd>
<dt> ‘<samp>-hex (<em>global</em>)</samp>’</dt>
<dd><p>When dumping packets, also dump the payload.
</p></dd>
<dt> ‘<samp>-re (<em>input</em>)</samp>’</dt>
<dd><p>Read input at native frame rate. Mainly used to simulate a grab device
or live input stream (e.g. when reading from a file). Should not be used
with actual grab devices or live input streams (where it can cause packet
loss).
</p></dd>
<dt> ‘<samp>-vsync <var>parameter</var></samp>’</dt>
<dd><p>Video sync method.
</p>
<dl compact="compact">
<dt> ‘<samp>passthrough</samp>’</dt>
<dd><p>Each frame is passed with its timestamp from the demuxer to the muxer.
</p></dd>
<dt> ‘<samp>cfr</samp>’</dt>
<dd><p>Frames will be duplicated and dropped to achieve exactly the requested
constant framerate.
</p></dd>
<dt> ‘<samp>vfr</samp>’</dt>
<dd><p>Frames are passed through with their timestamp or dropped so as to
prevent 2 frames from having the same timestamp.
</p></dd>
<dt> ‘<samp>auto</samp>’</dt>
<dd><p>Chooses between 1 and 2 depending on muxer capabilities. This is the
default method.
</p></dd>
</dl>
<p>With -map you can select from which stream the timestamps should be
taken. You can leave either video or audio unchanged and sync the
remaining stream(s) to the unchanged one.
</p>
</dd>
<dt> ‘<samp>-async <var>samples_per_second</var></samp>’</dt>
<dd><p>Audio sync method. "Stretches/squeezes" the audio stream to match the timestamps,
the parameter is the maximum samples per second by which the audio is changed.
-async 1 is a special case where only the start of the audio stream is corrected
without any later correction.
This option has been deprecated. Use the <code>asyncts</code> audio filter instead.
</p></dd>
<dt> ‘<samp>-copyts</samp>’</dt>
<dd><p>Copy timestamps from input to output.
</p></dd>
<dt> ‘<samp>-copytb</samp>’</dt>
<dd><p>Copy input stream time base from input to output when stream copying.
</p></dd>
<dt> ‘<samp>-shortest (<em>output</em>)</samp>’</dt>
<dd><p>Finish encoding when the shortest input stream ends.
</p></dd>
<dt> ‘<samp>-dts_delta_threshold</samp>’</dt>
<dd><p>Timestamp discontinuity delta threshold.
</p></dd>
<dt> ‘<samp>-muxdelay <var>seconds</var> (<em>input</em>)</samp>’</dt>
<dd><p>Set the maximum demux-decode delay.
</p></dd>
<dt> ‘<samp>-muxpreload <var>seconds</var> (<em>input</em>)</samp>’</dt>
<dd><p>Set the initial demux-decode delay.
</p></dd>
<dt> ‘<samp>-streamid <var>output-stream-index</var>:<var>new-value</var> (<em>output</em>)</samp>’</dt>
<dd><p>Assign a new stream-id value to an output stream. This option should be
specified prior to the output filename to which it applies.
For the situation where multiple output files exist, a streamid
may be reassigned to a different value.
</p>
<p>For example, to set the stream 0 PID to 33 and the stream 1 PID to 36 for
an output mpegts file:
</p><table><tr><td> </td><td><pre class="example">avconv -i infile -streamid 0:33 -streamid 1:36 out.ts
</pre></td></tr></table>
</dd>
<dt> ‘<samp>-bsf[:<var>stream_specifier</var>] <var>bitstream_filters</var> (<em>output,per-stream</em>)</samp>’</dt>
<dd><p>Set bitstream filters for matching streams. <var>bistream_filters</var> is
a comma-separated list of bitstream filters. Use the <code>-bsfs</code> option
to get the list of bitstream filters.
</p><table><tr><td> </td><td><pre class="example">avconv -i h264.mp4 -c:v copy -bsf:v h264_mp4toannexb -an out.h264
</pre></td></tr></table>
<table><tr><td> </td><td><pre class="example">avconv -i file.mov -an -vn -bsf:s mov2textsub -c:s copy -f rawvideo sub.txt
</pre></td></tr></table>
</dd>
<dt> ‘<samp>-tag[:<var>stream_specifier</var>] <var>codec_tag</var> (<em>input/output,per-stream</em>)</samp>’</dt>
<dd><p>Force a tag/fourcc for matching streams.
</p>
</dd>
<dt> ‘<samp>-filter_complex <var>filtergraph</var> (<em>global</em>)</samp>’</dt>
<dd><p>Define a complex filter graph, i.e. one with arbitrary number of inputs and/or
outputs. For simple graphs – those with one input and one output of the same
type – see the ‘<samp>-filter</samp>’ options. <var>filtergraph</var> is a description of
the filter graph, as described in <a href="#Filtergraph-syntax">Filtergraph syntax</a>.
</p>
<p>Input link labels must refer to input streams using the
<code>[file_index:stream_specifier]</code> syntax (i.e. the same as ‘<samp>-map</samp>’
uses). If <var>stream_specifier</var> matches multiple streams, the first one will be
used. An unlabeled input will be connected to the first unused input stream of
the matching type.
</p>
<p>Output link labels are referred to with ‘<samp>-map</samp>’. Unlabeled outputs are
added to the first output file.
</p>
<p>Note that with this option it is possible to use only lavfi sources without
normal input files.
</p>
<p>For example, to overlay an image over video
</p><table><tr><td> </td><td><pre class="example">avconv -i video.mkv -i image.png -filter_complex '[0:v][1:v]overlay[out]' -map
'[out]' out.mkv
</pre></td></tr></table>
<p>Here <code>[0:v]</code> refers to the first video stream in the first input file,
which is linked to the first (main) input of the overlay filter. Similarly the
first video stream in the second input is linked to the second (overlay) input
of overlay.
</p>
<p>Assuming there is only one video stream in each input file, we can omit input
labels, so the above is equivalent to
</p><table><tr><td> </td><td><pre class="example">avconv -i video.mkv -i image.png -filter_complex 'overlay[out]' -map
'[out]' out.mkv
</pre></td></tr></table>
<p>Furthermore we can omit the output label and the single output from the filter
graph will be added to the output file automatically, so we can simply write
</p><table><tr><td> </td><td><pre class="example">avconv -i video.mkv -i image.png -filter_complex 'overlay' out.mkv
</pre></td></tr></table>
<p>To generate 5 seconds of pure red video using lavfi <code>color</code> source:
</p><table><tr><td> </td><td><pre class="example">avconv -filter_complex 'color=red' -t 5 out.mkv
</pre></td></tr></table>
</dd>
<dt> ‘<samp>-filter_complex_script <var>filename</var> (<em>global</em>)</samp>’</dt>
<dd><p>This option is similar to ‘<samp>-filter_complex</samp>’, the only difference is that
its argument is the name of the file from which a complex filtergraph
description is to be read.
</p>
</dd>
<dt> ‘<samp>-accurate_seek (<em>input</em>)</samp>’</dt>
<dd><p>This option enables or disables accurate seeking in input files with the
‘<samp>-ss</samp>’ option. It is enabled by default, so seeking is accurate when
transcoding. Use ‘<samp>-noaccurate_seek</samp>’ to disable it, which may be useful
e.g. when copying some streams and transcoding the others.
</p>
</dd>
</dl>
<a name="Tips"></a>
<h1 class="chapter"><a href="avconv.html#toc-Tips">6. Tips</a></h1>
<ul>
<li>
For streaming at very low bitrate application, use a low frame rate
and a small GOP size. This is especially true for RealVideo where
the Linux player does not seem to be very fast, so it can miss
frames. An example is:
<table><tr><td> </td><td><pre class="example">avconv -g 3 -r 3 -t 10 -b 50k -s qcif -f rv10 /tmp/b.rm
</pre></td></tr></table>
</li><li>
The parameter ’q’ which is displayed while encoding is the current
quantizer. The value 1 indicates that a very good quality could
be achieved. The value 31 indicates the worst quality. If q=31 appears
too often, it means that the encoder cannot compress enough to meet
your bitrate. You must either increase the bitrate, decrease the
frame rate or decrease the frame size.
</li><li>
If your computer is not fast enough, you can speed up the
compression at the expense of the compression ratio. You can use
’-me zero’ to speed up motion estimation, and ’-g 0’ to disable
motion estimation completely (you have only I-frames, which means it
is about as good as JPEG compression).
</li><li>
To have very low audio bitrates, reduce the sampling frequency
(down to 22050 Hz for MPEG audio, 22050 or 11025 for AC-3).
</li><li>
To have a constant quality (but a variable bitrate), use the option
’-qscale n’ when ’n’ is between 1 (excellent quality) and 31 (worst
quality).
</li></ul>
<a name="Examples-1"></a>
<h1 class="chapter"><a href="avconv.html#toc-Examples-1">7. Examples</a></h1>
<a name="Preset-files"></a>
<h2 class="section"><a href="avconv.html#toc-Preset-files">7.1 Preset files</a></h2>
<p>A preset file contains a sequence of <var>option=value</var> pairs, one for
each line, specifying a sequence of options which can be specified also on
the command line. Lines starting with the hash (’#’) character are ignored and
are used to provide comments. Empty lines are also ignored. Check the
‘<tt>presets</tt>’ directory in the Libav source tree for examples.
</p>
<p>Preset files are specified with the <code>pre</code> option, this option takes a
preset name as input. Avconv searches for a file named <var>preset_name</var>.avpreset in
the directories ‘<tt>$AVCONV_DATADIR</tt>’ (if set), and ‘<tt>$HOME/.avconv</tt>’, and in
the data directory defined at configuration time (usually ‘<tt>$PREFIX/share/avconv</tt>’)
in that order. For example, if the argument is <code>libx264-max</code>, it will
search for the file ‘<tt>libx264-max.avpreset</tt>’.
</p>
<a name="Video-and-Audio-grabbing"></a>
<h2 class="section"><a href="avconv.html#toc-Video-and-Audio-grabbing">7.2 Video and Audio grabbing</a></h2>
<p>If you specify the input format and device then avconv can grab video
and audio directly.
</p>
<table><tr><td> </td><td><pre class="example">avconv -f oss -i /dev/dsp -f video4linux2 -i /dev/video0 /tmp/out.mpg
</pre></td></tr></table>
<p>Note that you must activate the right video source and channel before
launching avconv with any TV viewer such as
<a href="http://linux.bytesex.org/xawtv/">xawtv</a> by Gerd Knorr. You also
have to set the audio recording levels correctly with a
standard mixer.
</p>
<a name="X11-grabbing"></a>
<h2 class="section"><a href="avconv.html#toc-X11-grabbing">7.3 X11 grabbing</a></h2>
<p>Grab the X11 display with avconv via
</p>
<table><tr><td> </td><td><pre class="example">avconv -f x11grab -s cif -r 25 -i :0.0 /tmp/out.mpg
</pre></td></tr></table>
<p>0.0 is display.screen number of your X11 server, same as
the DISPLAY environment variable.
</p>
<table><tr><td> </td><td><pre class="example">avconv -f x11grab -s cif -r 25 -i :0.0+10,20 /tmp/out.mpg
</pre></td></tr></table>
<p>0.0 is display.screen number of your X11 server, same as the DISPLAY environment
variable. 10 is the x-offset and 20 the y-offset for the grabbing.
</p>
<a name="Video-and-Audio-file-format-conversion"></a>
<h2 class="section"><a href="avconv.html#toc-Video-and-Audio-file-format-conversion">7.4 Video and Audio file format conversion</a></h2>
<p>Any supported file format and protocol can serve as input to avconv:
</p>
<p>Examples:
</p><ul>
<li>
You can use YUV files as input:
<table><tr><td> </td><td><pre class="example">avconv -i /tmp/test%d.Y /tmp/out.mpg
</pre></td></tr></table>
<p>It will use the files:
</p><table><tr><td> </td><td><pre class="example">/tmp/test0.Y, /tmp/test0.U, /tmp/test0.V,
/tmp/test1.Y, /tmp/test1.U, /tmp/test1.V, etc...
</pre></td></tr></table>
<p>The Y files use twice the resolution of the U and V files. They are
raw files, without header. They can be generated by all decent video
decoders. You must specify the size of the image with the ‘<samp>-s</samp>’ option
if avconv cannot guess it.
</p>
</li><li>
You can input from a raw YUV420P file:
<table><tr><td> </td><td><pre class="example">avconv -i /tmp/test.yuv /tmp/out.avi
</pre></td></tr></table>
<p>test.yuv is a file containing raw YUV planar data. Each frame is composed
of the Y plane followed by the U and V planes at half vertical and
horizontal resolution.
</p>
</li><li>
You can output to a raw YUV420P file:
<table><tr><td> </td><td><pre class="example">avconv -i mydivx.avi hugefile.yuv
</pre></td></tr></table>
</li><li>
You can set several input files and output files:
<table><tr><td> </td><td><pre class="example">avconv -i /tmp/a.wav -s 640x480 -i /tmp/a.yuv /tmp/a.mpg
</pre></td></tr></table>
<p>Converts the audio file a.wav and the raw YUV video file a.yuv
to MPEG file a.mpg.
</p>
</li><li>
You can also do audio and video conversions at the same time:
<table><tr><td> </td><td><pre class="example">avconv -i /tmp/a.wav -ar 22050 /tmp/a.mp2
</pre></td></tr></table>
<p>Converts a.wav to MPEG audio at 22050 Hz sample rate.
</p>
</li><li>
You can encode to several formats at the same time and define a
mapping from input stream to output streams:
<table><tr><td> </td><td><pre class="example">avconv -i /tmp/a.wav -map 0:a -b 64k /tmp/a.mp2 -map 0:a -b 128k /tmp/b.mp2
</pre></td></tr></table>
<p>Converts a.wav to a.mp2 at 64 kbits and to b.mp2 at 128 kbits. ’-map
file:index’ specifies which input stream is used for each output
stream, in the order of the definition of output streams.
</p>
</li><li>
You can transcode decrypted VOBs:
<table><tr><td> </td><td><pre class="example">avconv -i snatch_1.vob -f avi -c:v mpeg4 -b:v 800k -g 300 -bf 2 -c:a libmp3lame -b:a 128k snatch.avi
</pre></td></tr></table>
<p>This is a typical DVD ripping example; the input is a VOB file, the
output an AVI file with MPEG-4 video and MP3 audio. Note that in this
command we use B-frames so the MPEG-4 stream is DivX5 compatible, and
GOP size is 300 which means one intra frame every 10 seconds for 29.97fps
input video. Furthermore, the audio stream is MP3-encoded so you need
to enable LAME support by passing <code>--enable-libmp3lame</code> to configure.
The mapping is particularly useful for DVD transcoding
to get the desired audio language.
</p>
<p>NOTE: To see the supported input formats, use <code>avconv -formats</code>.
</p>
</li><li>
You can extract images from a video, or create a video from many images:
<p>For extracting images from a video:
</p><table><tr><td> </td><td><pre class="example">avconv -i foo.avi -r 1 -s WxH -f image2 foo-%03d.jpeg
</pre></td></tr></table>
<p>This will extract one video frame per second from the video and will
output them in files named ‘<tt>foo-001.jpeg</tt>’, ‘<tt>foo-002.jpeg</tt>’,
etc. Images will be rescaled to fit the new WxH values.
</p>
<p>If you want to extract just a limited number of frames, you can use the
above command in combination with the -vframes or -t option, or in
combination with -ss to start extracting from a certain point in time.
</p>
<p>For creating a video from many images:
</p><table><tr><td> </td><td><pre class="example">avconv -f image2 -i foo-%03d.jpeg -r 12 -s WxH foo.avi
</pre></td></tr></table>
<p>The syntax <code>foo-%03d.jpeg</code> specifies to use a decimal number
composed of three digits padded with zeroes to express the sequence
number. It is the same syntax supported by the C printf function, but
only formats accepting a normal integer are suitable.
</p>
</li><li>
You can put many streams of the same type in the output:
<table><tr><td> </td><td><pre class="example">avconv -i test1.avi -i test2.avi -map 1:1 -map 1:0 -map 0:1 -map 0:0 -c copy -y test12.nut
</pre></td></tr></table>
<p>The resulting output file ‘<tt>test12.nut</tt>’ will contain the first four streams
from the input files in reverse order.
</p>
</li><li>
To force CBR video output:
<table><tr><td> </td><td><pre class="example">avconv -i myfile.avi -b 4000k -minrate 4000k -maxrate 4000k -bufsize 1835k out.m2v
</pre></td></tr></table>
</li><li>
The four options lmin, lmax, mblmin and mblmax use ’lambda’ units,
but you may use the QP2LAMBDA constant to easily convert from ’q’ units:
<table><tr><td> </td><td><pre class="example">avconv -i src.ext -lmax 21*QP2LAMBDA dst.ext
</pre></td></tr></table>
</li></ul>
<a name="Expression-Evaluation"></a>
<h1 class="chapter"><a href="avconv.html#toc-Expression-Evaluation">8. Expression Evaluation</a></h1>
<p>When evaluating an arithmetic expression, Libav uses an internal
formula evaluator, implemented through the ‘<tt>libavutil/eval.h</tt>’
interface.
</p>
<p>An expression may contain unary, binary operators, constants, and
functions.
</p>
<p>Two expressions <var>expr1</var> and <var>expr2</var> can be combined to form
another expression "<var>expr1</var>;<var>expr2</var>".
<var>expr1</var> and <var>expr2</var> are evaluated in turn, and the new
expression evaluates to the value of <var>expr2</var>.
</p>
<p>The following binary operators are available: <code>+</code>, <code>-</code>,
<code>*</code>, <code>/</code>, <code>^</code>.
</p>
<p>The following unary operators are available: <code>+</code>, <code>-</code>.
</p>
<p>The following functions are available:
</p><dl compact="compact">
<dt> ‘<samp>sinh(x)</samp>’</dt>
<dt> ‘<samp>cosh(x)</samp>’</dt>
<dt> ‘<samp>tanh(x)</samp>’</dt>
<dt> ‘<samp>sin(x)</samp>’</dt>
<dt> ‘<samp>cos(x)</samp>’</dt>
<dt> ‘<samp>tan(x)</samp>’</dt>
<dt> ‘<samp>atan(x)</samp>’</dt>
<dt> ‘<samp>asin(x)</samp>’</dt>
<dt> ‘<samp>acos(x)</samp>’</dt>
<dt> ‘<samp>exp(x)</samp>’</dt>
<dt> ‘<samp>log(x)</samp>’</dt>
<dt> ‘<samp>abs(x)</samp>’</dt>
<dt> ‘<samp>squish(x)</samp>’</dt>
<dt> ‘<samp>gauss(x)</samp>’</dt>
<dt> ‘<samp>isinf(x)</samp>’</dt>
<dd><p>Return 1.0 if <var>x</var> is +/-INFINITY, 0.0 otherwise.
</p></dd>
<dt> ‘<samp>isnan(x)</samp>’</dt>
<dd><p>Return 1.0 if <var>x</var> is NAN, 0.0 otherwise.
</p>
</dd>
<dt> ‘<samp>mod(x, y)</samp>’</dt>
<dt> ‘<samp>max(x, y)</samp>’</dt>
<dt> ‘<samp>min(x, y)</samp>’</dt>
<dt> ‘<samp>eq(x, y)</samp>’</dt>
<dt> ‘<samp>gte(x, y)</samp>’</dt>
<dt> ‘<samp>gt(x, y)</samp>’</dt>
<dt> ‘<samp>lte(x, y)</samp>’</dt>
<dt> ‘<samp>lt(x, y)</samp>’</dt>
<dt> ‘<samp>st(var, expr)</samp>’</dt>
<dd><p>Allow to store the value of the expression <var>expr</var> in an internal
variable. <var>var</var> specifies the number of the variable where to
store the value, and it is a value ranging from 0 to 9. The function
returns the value stored in the internal variable.
</p>
</dd>
<dt> ‘<samp>ld(var)</samp>’</dt>
<dd><p>Allow to load the value of the internal variable with number
<var>var</var>, which was previously stored with st(<var>var</var>, <var>expr</var>).
The function returns the loaded value.
</p>
</dd>
<dt> ‘<samp>while(cond, expr)</samp>’</dt>
<dd><p>Evaluate expression <var>expr</var> while the expression <var>cond</var> is
non-zero, and returns the value of the last <var>expr</var> evaluation, or
NAN if <var>cond</var> was always false.
</p>
</dd>
<dt> ‘<samp>ceil(expr)</samp>’</dt>
<dd><p>Round the value of expression <var>expr</var> upwards to the nearest
integer. For example, "ceil(1.5)" is "2.0".
</p>
</dd>
<dt> ‘<samp>floor(expr)</samp>’</dt>
<dd><p>Round the value of expression <var>expr</var> downwards to the nearest
integer. For example, "floor(-1.5)" is "-2.0".
</p>
</dd>
<dt> ‘<samp>trunc(expr)</samp>’</dt>
<dd><p>Round the value of expression <var>expr</var> towards zero to the nearest
integer. For example, "trunc(-1.5)" is "-1.0".
</p>
</dd>
<dt> ‘<samp>sqrt(expr)</samp>’</dt>
<dd><p>Compute the square root of <var>expr</var>. This is equivalent to
"(<var>expr</var>)^.5".
</p>
</dd>
<dt> ‘<samp>not(expr)</samp>’</dt>
<dd><p>Return 1.0 if <var>expr</var> is zero, 0.0 otherwise.
</p></dd>
</dl>
<p>Note that:
</p>
<p><code>*</code> works like AND
</p>
<p><code>+</code> works like OR
</p>
<p>thus
</p><table><tr><td> </td><td><pre class="example">if A then B else C
</pre></td></tr></table>
<p>is equivalent to
</p><table><tr><td> </td><td><pre class="example">A*B + not(A)*C
</pre></td></tr></table>
<p>In your C code, you can extend the list of unary and binary functions,
and define recognized constants, so that they are available for your
expressions.
</p>
<p>The evaluator also recognizes the International System number
postfixes. If ’i’ is appended after the postfix, powers of 2 are used
instead of powers of 10. The ’B’ postfix multiplies the value for 8,
and can be appended after another postfix or used alone. This allows
using for example ’KB’, ’MiB’, ’G’ and ’B’ as postfix.
</p>
<p>Follows the list of available International System postfixes, with
indication of the corresponding powers of 10 and of 2.
</p><dl compact="compact">
<dt> ‘<samp>y</samp>’</dt>
<dd><p>-24 / -80
</p></dd>
<dt> ‘<samp>z</samp>’</dt>
<dd><p>-21 / -70
</p></dd>
<dt> ‘<samp>a</samp>’</dt>
<dd><p>-18 / -60
</p></dd>
<dt> ‘<samp>f</samp>’</dt>
<dd><p>-15 / -50
</p></dd>
<dt> ‘<samp>p</samp>’</dt>
<dd><p>-12 / -40
</p></dd>
<dt> ‘<samp>n</samp>’</dt>
<dd><p>-9 / -30
</p></dd>
<dt> ‘<samp>u</samp>’</dt>
<dd><p>-6 / -20
</p></dd>
<dt> ‘<samp>m</samp>’</dt>
<dd><p>-3 / -10
</p></dd>
<dt> ‘<samp>c</samp>’</dt>
<dd><p>-2
</p></dd>
<dt> ‘<samp>d</samp>’</dt>
<dd><p>-1
</p></dd>
<dt> ‘<samp>h</samp>’</dt>
<dd><p>2
</p></dd>
<dt> ‘<samp>k</samp>’</dt>
<dd><p>3 / 10
</p></dd>
<dt> ‘<samp>K</samp>’</dt>
<dd><p>3 / 10
</p></dd>
<dt> ‘<samp>M</samp>’</dt>
<dd><p>6 / 20
</p></dd>
<dt> ‘<samp>G</samp>’</dt>
<dd><p>9 / 30
</p></dd>
<dt> ‘<samp>T</samp>’</dt>
<dd><p>12 / 40
</p></dd>
<dt> ‘<samp>P</samp>’</dt>
<dd><p>15 / 40
</p></dd>
<dt> ‘<samp>E</samp>’</dt>
<dd><p>18 / 50
</p></dd>
<dt> ‘<samp>Z</samp>’</dt>
<dd><p>21 / 60
</p></dd>
<dt> ‘<samp>Y</samp>’</dt>
<dd><p>24 / 70
</p></dd>
</dl>
<a name="Decoders"></a>
<h1 class="chapter"><a href="avconv.html#toc-Decoders">9. Decoders</a></h1>
<p>Decoders are configured elements in Libav which allow the decoding of
multimedia streams.
</p>
<p>When you configure your Libav build, all the supported native decoders
are enabled by default. Decoders requiring an external library must be enabled
manually via the corresponding <code>--enable-lib</code> option. You can list all
available decoders using the configure option <code>--list-decoders</code>.
</p>
<p>You can disable all the decoders with the configure option
<code>--disable-decoders</code> and selectively enable / disable single decoders
with the options <code>--enable-decoder=<var>DECODER</var></code> /
<code>--disable-decoder=<var>DECODER</var></code>.
</p>
<p>The option <code>-decoders</code> of the av* tools will display the list of
enabled decoders.
</p>
<a name="Audio-Decoders"></a>
<h1 class="chapter"><a href="avconv.html#toc-Audio-Decoders">10. Audio Decoders</a></h1>
<p>A description of some of the currently available audio decoders
follows.
</p>
<a name="ac3"></a>
<h2 class="section"><a href="avconv.html#toc-ac3">10.1 ac3</a></h2>
<p>AC-3 audio decoder.
</p>
<p>This decoder implements part of ATSC A/52:2010 and ETSI TS 102 366, as well as
the undocumented RealAudio 3 (a.k.a. dnet).
</p>
<a name="AC_002d3-Decoder-Options"></a>
<h4 class="subsubsection"><a href="avconv.html#toc-AC_002d3-Decoder-Options">10.1.0.1 AC-3 Decoder Options</a></h4>
<dl compact="compact">
<dt> ‘<samp>-drc_scale <var>value</var></samp>’</dt>
<dd><p>Dynamic Range Scale Factor. The factor to apply to dynamic range values
from the AC-3 stream. This factor is applied exponentially.
There are 3 notable scale factor ranges:
</p><dl compact="compact">
<dt> ‘<samp>drc_scale == 0</samp>’</dt>
<dd><p>DRC disabled. Produces full range audio.
</p></dd>
<dt> ‘<samp>0 < drc_scale <= 1</samp>’</dt>
<dd><p>DRC enabled. Applies a fraction of the stream DRC value.
Audio reproduction is between full range and full compression.
</p></dd>
<dt> ‘<samp>drc_scale > 1</samp>’</dt>
<dd><p>DRC enabled. Applies drc_scale asymmetrically.
Loud sounds are fully compressed. Soft sounds are enhanced.
</p></dd>
</dl>
</dd>
</dl>
<a name="Encoders"></a>
<h1 class="chapter"><a href="avconv.html#toc-Encoders">11. Encoders</a></h1>
<p>Encoders are configured elements in Libav which allow the encoding of
multimedia streams.
</p>
<p>When you configure your Libav build, all the supported native encoders
are enabled by default. Encoders requiring an external library must be enabled
manually via the corresponding <code>--enable-lib</code> option. You can list all
available encoders using the configure option <code>--list-encoders</code>.
</p>
<p>You can disable all the encoders with the configure option
<code>--disable-encoders</code> and selectively enable / disable single encoders
with the options <code>--enable-encoder=<var>ENCODER</var></code> /
<code>--disable-encoder=<var>ENCODER</var></code>.
</p>
<p>The option <code>-encoders</code> of the av* tools will display the list of
enabled encoders.
</p>
<a name="Audio-Encoders"></a>
<h1 class="chapter"><a href="avconv.html#toc-Audio-Encoders">12. Audio Encoders</a></h1>
<p>A description of some of the currently available audio encoders
follows.
</p>
<a name="ac3-and-ac3_005ffixed"></a>
<h2 class="section"><a href="avconv.html#toc-ac3-and-ac3_005ffixed">12.1 ac3 and ac3_fixed</a></h2>
<p>AC-3 audio encoders.
</p>
<p>These encoders implement part of ATSC A/52:2010 and ETSI TS 102 366, as well as
the undocumented RealAudio 3 (a.k.a. dnet).
</p>
<p>The <var>ac3</var> encoder uses floating-point math, while the <var>ac3_fixed</var>
encoder only uses fixed-point integer math. This does not mean that one is
always faster, just that one or the other may be better suited to a
particular system. The floating-point encoder will generally produce better
quality audio for a given bitrate. The <var>ac3_fixed</var> encoder is not the
default codec for any of the output formats, so it must be specified explicitly
using the option <code>-acodec ac3_fixed</code> in order to use it.
</p>
<a name="AC_002d3-Metadata"></a>
<h3 class="subsection"><a href="avconv.html#toc-AC_002d3-Metadata">12.1.1 AC-3 Metadata</a></h3>
<p>The AC-3 metadata options are used to set parameters that describe the audio,
but in most cases do not affect the audio encoding itself. Some of the options
do directly affect or influence the decoding and playback of the resulting
bitstream, while others are just for informational purposes. A few of the
options will add bits to the output stream that could otherwise be used for
audio data, and will thus affect the quality of the output. Those will be
indicated accordingly with a note in the option list below.
</p>
<p>These parameters are described in detail in several publicly-available
documents.
</p><ul>
<li> <a href="http://www.atsc.org/cms/standards/a_52-2010.pdf">A/52:2010 - Digital Audio Compression (AC-3) (E-AC-3) Standard</a>
</li><li> <a href="http://www.atsc.org/cms/standards/a_54a_with_corr_1.pdf">A/54 - Guide to the Use of the ATSC Digital Television Standard</a>
</li><li> <a href="http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Professional/18_Metadata.Guide.pdf">Dolby Metadata Guide</a>
</li><li> <a href="http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Professional/46_DDEncodingGuidelines.pdf">Dolby Digital Professional Encoding Guidelines</a>
</li></ul>
<a name="Metadata-Control-Options"></a>
<h4 class="subsubsection"><a href="avconv.html#toc-Metadata-Control-Options">12.1.1.1 Metadata Control Options</a></h4>
<dl compact="compact">
<dt> ‘<samp>-per_frame_metadata <var>boolean</var></samp>’</dt>
<dd><p>Allow Per-Frame Metadata. Specifies if the encoder should check for changing
metadata for each frame.
</p><dl compact="compact">
<dt> ‘<samp>0</samp>’</dt>
<dd><p>The metadata values set at initialization will be used for every frame in the
stream. (default)
</p></dd>
<dt> ‘<samp>1</samp>’</dt>
<dd><p>Metadata values can be changed before encoding each frame.
</p></dd>
</dl>
</dd>
</dl>
<a name="Downmix-Levels"></a>
<h4 class="subsubsection"><a href="avconv.html#toc-Downmix-Levels">12.1.1.2 Downmix Levels</a></h4>
<dl compact="compact">
<dt> ‘<samp>-center_mixlev <var>level</var></samp>’</dt>
<dd><p>Center Mix Level. The amount of gain the decoder should apply to the center
channel when downmixing to stereo. This field will only be written to the
bitstream if a center channel is present. The value is specified as a scale
factor. There are 3 valid values:
</p><dl compact="compact">
<dt> ‘<samp>0.707</samp>’</dt>
<dd><p>Apply -3dB gain
</p></dd>
<dt> ‘<samp>0.595</samp>’</dt>
<dd><p>Apply -4.5dB gain (default)
</p></dd>
<dt> ‘<samp>0.500</samp>’</dt>
<dd><p>Apply -6dB gain
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-surround_mixlev <var>level</var></samp>’</dt>
<dd><p>Surround Mix Level. The amount of gain the decoder should apply to the surround
channel(s) when downmixing to stereo. This field will only be written to the
bitstream if one or more surround channels are present. The value is specified
as a scale factor. There are 3 valid values:
</p><dl compact="compact">
<dt> ‘<samp>0.707</samp>’</dt>
<dd><p>Apply -3dB gain
</p></dd>
<dt> ‘<samp>0.500</samp>’</dt>
<dd><p>Apply -6dB gain (default)
</p></dd>
<dt> ‘<samp>0.000</samp>’</dt>
<dd><p>Silence Surround Channel(s)
</p></dd>
</dl>
</dd>
</dl>
<a name="Audio-Production-Information"></a>
<h4 class="subsubsection"><a href="avconv.html#toc-Audio-Production-Information">12.1.1.3 Audio Production Information</a></h4>
<p>Audio Production Information is optional information describing the mixing
environment. Either none or both of the fields are written to the bitstream.
</p>
<dl compact="compact">
<dt> ‘<samp>-mixing_level <var>number</var></samp>’</dt>
<dd><p>Mixing Level. Specifies peak sound pressure level (SPL) in the production
environment when the mix was mastered. Valid values are 80 to 111, or -1 for
unknown or not indicated. The default value is -1, but that value cannot be
used if the Audio Production Information is written to the bitstream. Therefore,
if the <code>room_type</code> option is not the default value, the <code>mixing_level</code>
option must not be -1.
</p>
</dd>
<dt> ‘<samp>-room_type <var>type</var></samp>’</dt>
<dd><p>Room Type. Describes the equalization used during the final mixing session at
the studio or on the dubbing stage. A large room is a dubbing stage with the
industry standard X-curve equalization; a small room has flat equalization.
This field will not be written to the bitstream if both the <code>mixing_level</code>
option and the <code>room_type</code> option have the default values.
</p><dl compact="compact">
<dt> ‘<samp>0</samp>’</dt>
<dt> ‘<samp>notindicated</samp>’</dt>
<dd><p>Not Indicated (default)
</p></dd>
<dt> ‘<samp>1</samp>’</dt>
<dt> ‘<samp>large</samp>’</dt>
<dd><p>Large Room
</p></dd>
<dt> ‘<samp>2</samp>’</dt>
<dt> ‘<samp>small</samp>’</dt>
<dd><p>Small Room
</p></dd>
</dl>
</dd>
</dl>
<a name="Other-Metadata-Options"></a>
<h4 class="subsubsection"><a href="avconv.html#toc-Other-Metadata-Options">12.1.1.4 Other Metadata Options</a></h4>
<dl compact="compact">
<dt> ‘<samp>-copyright <var>boolean</var></samp>’</dt>
<dd><p>Copyright Indicator. Specifies whether a copyright exists for this audio.
</p><dl compact="compact">
<dt> ‘<samp>0</samp>’</dt>
<dt> ‘<samp>off</samp>’</dt>
<dd><p>No Copyright Exists (default)
</p></dd>
<dt> ‘<samp>1</samp>’</dt>
<dt> ‘<samp>on</samp>’</dt>
<dd><p>Copyright Exists
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-dialnorm <var>value</var></samp>’</dt>
<dd><p>Dialogue Normalization. Indicates how far the average dialogue level of the
program is below digital 100% full scale (0 dBFS). This parameter determines a
level shift during audio reproduction that sets the average volume of the
dialogue to a preset level. The goal is to match volume level between program
sources. A value of -31dB will result in no volume level change, relative to
the source volume, during audio reproduction. Valid values are whole numbers in
the range -31 to -1, with -31 being the default.
</p>
</dd>
<dt> ‘<samp>-dsur_mode <var>mode</var></samp>’</dt>
<dd><p>Dolby Surround Mode. Specifies whether the stereo signal uses Dolby Surround
(Pro Logic). This field will only be written to the bitstream if the audio
stream is stereo. Using this option does <b>NOT</b> mean the encoder will actually
apply Dolby Surround processing.
</p><dl compact="compact">
<dt> ‘<samp>0</samp>’</dt>
<dt> ‘<samp>notindicated</samp>’</dt>
<dd><p>Not Indicated (default)
</p></dd>
<dt> ‘<samp>1</samp>’</dt>
<dt> ‘<samp>off</samp>’</dt>
<dd><p>Not Dolby Surround Encoded
</p></dd>
<dt> ‘<samp>2</samp>’</dt>
<dt> ‘<samp>on</samp>’</dt>
<dd><p>Dolby Surround Encoded
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-original <var>boolean</var></samp>’</dt>
<dd><p>Original Bit Stream Indicator. Specifies whether this audio is from the
original source and not a copy.
</p><dl compact="compact">
<dt> ‘<samp>0</samp>’</dt>
<dt> ‘<samp>off</samp>’</dt>
<dd><p>Not Original Source
</p></dd>
<dt> ‘<samp>1</samp>’</dt>
<dt> ‘<samp>on</samp>’</dt>
<dd><p>Original Source (default)
</p></dd>
</dl>
</dd>
</dl>
<a name="Extended-Bitstream-Information"></a>
<h3 class="subsection"><a href="avconv.html#toc-Extended-Bitstream-Information">12.1.2 Extended Bitstream Information</a></h3>
<p>The extended bitstream options are part of the Alternate Bit Stream Syntax as
specified in Annex D of the A/52:2010 standard. It is grouped into 2 parts.
If any one parameter in a group is specified, all values in that group will be
written to the bitstream. Default values are used for those that are written
but have not been specified. If the mixing levels are written, the decoder
will use these values instead of the ones specified in the <code>center_mixlev</code>
and <code>surround_mixlev</code> options if it supports the Alternate Bit Stream
Syntax.
</p>
<a name="Extended-Bitstream-Information-_002d-Part-1"></a>
<h4 class="subsubsection"><a href="avconv.html#toc-Extended-Bitstream-Information-_002d-Part-1">12.1.2.1 Extended Bitstream Information - Part 1</a></h4>
<dl compact="compact">
<dt> ‘<samp>-dmix_mode <var>mode</var></samp>’</dt>
<dd><p>Preferred Stereo Downmix Mode. Allows the user to select either Lt/Rt
(Dolby Surround) or Lo/Ro (normal stereo) as the preferred stereo downmix mode.
</p><dl compact="compact">
<dt> ‘<samp>0</samp>’</dt>
<dt> ‘<samp>notindicated</samp>’</dt>
<dd><p>Not Indicated (default)
</p></dd>
<dt> ‘<samp>1</samp>’</dt>
<dt> ‘<samp>ltrt</samp>’</dt>
<dd><p>Lt/Rt Downmix Preferred
</p></dd>
<dt> ‘<samp>2</samp>’</dt>
<dt> ‘<samp>loro</samp>’</dt>
<dd><p>Lo/Ro Downmix Preferred
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-ltrt_cmixlev <var>level</var></samp>’</dt>
<dd><p>Lt/Rt Center Mix Level. The amount of gain the decoder should apply to the
center channel when downmixing to stereo in Lt/Rt mode.
</p><dl compact="compact">
<dt> ‘<samp>1.414</samp>’</dt>
<dd><p>Apply +3dB gain
</p></dd>
<dt> ‘<samp>1.189</samp>’</dt>
<dd><p>Apply +1.5dB gain
</p></dd>
<dt> ‘<samp>1.000</samp>’</dt>
<dd><p>Apply 0dB gain
</p></dd>
<dt> ‘<samp>0.841</samp>’</dt>
<dd><p>Apply -1.5dB gain
</p></dd>
<dt> ‘<samp>0.707</samp>’</dt>
<dd><p>Apply -3.0dB gain
</p></dd>
<dt> ‘<samp>0.595</samp>’</dt>
<dd><p>Apply -4.5dB gain (default)
</p></dd>
<dt> ‘<samp>0.500</samp>’</dt>
<dd><p>Apply -6.0dB gain
</p></dd>
<dt> ‘<samp>0.000</samp>’</dt>
<dd><p>Silence Center Channel
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-ltrt_surmixlev <var>level</var></samp>’</dt>
<dd><p>Lt/Rt Surround Mix Level. The amount of gain the decoder should apply to the
surround channel(s) when downmixing to stereo in Lt/Rt mode.
</p><dl compact="compact">
<dt> ‘<samp>0.841</samp>’</dt>
<dd><p>Apply -1.5dB gain
</p></dd>
<dt> ‘<samp>0.707</samp>’</dt>
<dd><p>Apply -3.0dB gain
</p></dd>
<dt> ‘<samp>0.595</samp>’</dt>
<dd><p>Apply -4.5dB gain
</p></dd>
<dt> ‘<samp>0.500</samp>’</dt>
<dd><p>Apply -6.0dB gain (default)
</p></dd>
<dt> ‘<samp>0.000</samp>’</dt>
<dd><p>Silence Surround Channel(s)
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-loro_cmixlev <var>level</var></samp>’</dt>
<dd><p>Lo/Ro Center Mix Level. The amount of gain the decoder should apply to the
center channel when downmixing to stereo in Lo/Ro mode.
</p><dl compact="compact">
<dt> ‘<samp>1.414</samp>’</dt>
<dd><p>Apply +3dB gain
</p></dd>
<dt> ‘<samp>1.189</samp>’</dt>
<dd><p>Apply +1.5dB gain
</p></dd>
<dt> ‘<samp>1.000</samp>’</dt>
<dd><p>Apply 0dB gain
</p></dd>
<dt> ‘<samp>0.841</samp>’</dt>
<dd><p>Apply -1.5dB gain
</p></dd>
<dt> ‘<samp>0.707</samp>’</dt>
<dd><p>Apply -3.0dB gain
</p></dd>
<dt> ‘<samp>0.595</samp>’</dt>
<dd><p>Apply -4.5dB gain (default)
</p></dd>
<dt> ‘<samp>0.500</samp>’</dt>
<dd><p>Apply -6.0dB gain
</p></dd>
<dt> ‘<samp>0.000</samp>’</dt>
<dd><p>Silence Center Channel
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-loro_surmixlev <var>level</var></samp>’</dt>
<dd><p>Lo/Ro Surround Mix Level. The amount of gain the decoder should apply to the
surround channel(s) when downmixing to stereo in Lo/Ro mode.
</p><dl compact="compact">
<dt> ‘<samp>0.841</samp>’</dt>
<dd><p>Apply -1.5dB gain
</p></dd>
<dt> ‘<samp>0.707</samp>’</dt>
<dd><p>Apply -3.0dB gain
</p></dd>
<dt> ‘<samp>0.595</samp>’</dt>
<dd><p>Apply -4.5dB gain
</p></dd>
<dt> ‘<samp>0.500</samp>’</dt>
<dd><p>Apply -6.0dB gain (default)
</p></dd>
<dt> ‘<samp>0.000</samp>’</dt>
<dd><p>Silence Surround Channel(s)
</p></dd>
</dl>
</dd>
</dl>
<a name="Extended-Bitstream-Information-_002d-Part-2"></a>
<h4 class="subsubsection"><a href="avconv.html#toc-Extended-Bitstream-Information-_002d-Part-2">12.1.2.2 Extended Bitstream Information - Part 2</a></h4>
<dl compact="compact">
<dt> ‘<samp>-dsurex_mode <var>mode</var></samp>’</dt>
<dd><p>Dolby Surround EX Mode. Indicates whether the stream uses Dolby Surround EX
(7.1 matrixed to 5.1). Using this option does <b>NOT</b> mean the encoder will actually
apply Dolby Surround EX processing.
</p><dl compact="compact">
<dt> ‘<samp>0</samp>’</dt>
<dt> ‘<samp>notindicated</samp>’</dt>
<dd><p>Not Indicated (default)
</p></dd>
<dt> ‘<samp>1</samp>’</dt>
<dt> ‘<samp>on</samp>’</dt>
<dd><p>Dolby Surround EX Off
</p></dd>
<dt> ‘<samp>2</samp>’</dt>
<dt> ‘<samp>off</samp>’</dt>
<dd><p>Dolby Surround EX On
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-dheadphone_mode <var>mode</var></samp>’</dt>
<dd><p>Dolby Headphone Mode. Indicates whether the stream uses Dolby Headphone
encoding (multi-channel matrixed to 2.0 for use with headphones). Using this
option does <b>NOT</b> mean the encoder will actually apply Dolby Headphone
processing.
</p><dl compact="compact">
<dt> ‘<samp>0</samp>’</dt>
<dt> ‘<samp>notindicated</samp>’</dt>
<dd><p>Not Indicated (default)
</p></dd>
<dt> ‘<samp>1</samp>’</dt>
<dt> ‘<samp>on</samp>’</dt>
<dd><p>Dolby Headphone Off
</p></dd>
<dt> ‘<samp>2</samp>’</dt>
<dt> ‘<samp>off</samp>’</dt>
<dd><p>Dolby Headphone On
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-ad_conv_type <var>type</var></samp>’</dt>
<dd><p>A/D Converter Type. Indicates whether the audio has passed through HDCD A/D
conversion.
</p><dl compact="compact">
<dt> ‘<samp>0</samp>’</dt>
<dt> ‘<samp>standard</samp>’</dt>
<dd><p>Standard A/D Converter (default)
</p></dd>
<dt> ‘<samp>1</samp>’</dt>
<dt> ‘<samp>hdcd</samp>’</dt>
<dd><p>HDCD A/D Converter
</p></dd>
</dl>
</dd>
</dl>
<a name="Other-AC_002d3-Encoding-Options"></a>
<h3 class="subsection"><a href="avconv.html#toc-Other-AC_002d3-Encoding-Options">12.1.3 Other AC-3 Encoding Options</a></h3>
<dl compact="compact">
<dt> ‘<samp>-stereo_rematrixing <var>boolean</var></samp>’</dt>
<dd><p>Stereo Rematrixing. Enables/Disables use of rematrixing for stereo input. This
is an optional AC-3 feature that increases quality by selectively encoding
the left/right channels as mid/side. This option is enabled by default, and it
is highly recommended that it be left as enabled except for testing purposes.
</p>
</dd>
</dl>
<a name="Floating_002dPoint_002dOnly-AC_002d3-Encoding-Options"></a>
<h3 class="subheading">Floating-Point-Only AC-3 Encoding Options</h3>
<p>These options are only valid for the floating-point encoder and do not exist
for the fixed-point encoder due to the corresponding features not being
implemented in fixed-point.
</p>
<dl compact="compact">
<dt> ‘<samp>-channel_coupling <var>boolean</var></samp>’</dt>
<dd><p>Enables/Disables use of channel coupling, which is an optional AC-3 feature
that increases quality by combining high frequency information from multiple
channels into a single channel. The per-channel high frequency information is
sent with less accuracy in both the frequency and time domains. This allows
more bits to be used for lower frequencies while preserving enough information
to reconstruct the high frequencies. This option is enabled by default for the
floating-point encoder and should generally be left as enabled except for
testing purposes or to increase encoding speed.
</p><dl compact="compact">
<dt> ‘<samp>-1</samp>’</dt>
<dt> ‘<samp>auto</samp>’</dt>
<dd><p>Selected by Encoder (default)
</p></dd>
<dt> ‘<samp>0</samp>’</dt>
<dt> ‘<samp>off</samp>’</dt>
<dd><p>Disable Channel Coupling
</p></dd>
<dt> ‘<samp>1</samp>’</dt>
<dt> ‘<samp>on</samp>’</dt>
<dd><p>Enable Channel Coupling
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-cpl_start_band <var>number</var></samp>’</dt>
<dd><p>Coupling Start Band. Sets the channel coupling start band, from 1 to 15. If a
value higher than the bandwidth is used, it will be reduced to 1 less than the
coupling end band. If <var>auto</var> is used, the start band will be determined by
the encoder based on the bit rate, sample rate, and channel layout. This option
has no effect if channel coupling is disabled.
</p><dl compact="compact">
<dt> ‘<samp>-1</samp>’</dt>
<dt> ‘<samp>auto</samp>’</dt>
<dd><p>Selected by Encoder (default)
</p></dd>
</dl>
</dd>
</dl>
<a name="libwavpack"></a>
<h2 class="section"><a href="avconv.html#toc-libwavpack">12.2 libwavpack</a></h2>
<p>A wrapper providing WavPack encoding through libwavpack.
</p>
<p>Only lossless mode using 32-bit integer samples is supported currently.
The ‘<samp>compression_level</samp>’ option can be used to control speed vs.
compression tradeoff, with the values mapped to libwavpack as follows:
</p>
<dl compact="compact">
<dt> ‘<samp>0</samp>’</dt>
<dd><p>Fast mode - corresponding to the wavpack ‘<samp>-f</samp>’ option.
</p>
</dd>
<dt> ‘<samp>1</samp>’</dt>
<dd><p>Normal (default) settings.
</p>
</dd>
<dt> ‘<samp>2</samp>’</dt>
<dd><p>High quality - corresponding to the wavpack ‘<samp>-h</samp>’ option.
</p>
</dd>
<dt> ‘<samp>3</samp>’</dt>
<dd><p>Very high quality - corresponding to the wavpack ‘<samp>-hh</samp>’ option.
</p>
</dd>
<dt> ‘<samp>4-8</samp>’</dt>
<dd><p>Same as 3, but with extra processing enabled - corresponding to the wavpack
‘<samp>-x</samp>’ option. I.e. 4 is the same as ‘<samp>-x2</samp>’ and 8 is the same as
‘<samp>-x6</samp>’.
</p>
</dd>
</dl>
<a name="Video-Encoders"></a>
<h1 class="chapter"><a href="avconv.html#toc-Video-Encoders">13. Video Encoders</a></h1>
<a name="libwebp"></a>
<h2 class="section"><a href="avconv.html#toc-libwebp">13.1 libwebp</a></h2>
<p>libwebp WebP Image encoder wrapper
</p>
<p>libwebp is Google’s official encoder for WebP images. It can encode in either
lossy or lossless mode. Lossy images are essentially a wrapper around a VP8
frame. Lossless images are a separate codec developed by Google.
</p>
<a name="Pixel-Format"></a>
<h3 class="subsection"><a href="avconv.html#toc-Pixel-Format">13.1.1 Pixel Format</a></h3>
<p>Currently, libwebp only supports YUV420 for lossy and RGB for lossless due
to limitations of the format and libwebp. Alpha is supported for either mode.
Because of API limitations, if RGB is passed in when encoding lossy or YUV is
passed in for encoding lossless, the pixel format will automatically be
converted using functions from libwebp. This is not ideal and is done only for
convenience.
</p>
<a name="Options"></a>
<h3 class="subsection"><a href="avconv.html#toc-Options">13.1.2 Options</a></h3>
<dl compact="compact">
<dt> ‘<samp>-lossless <var>boolean</var></samp>’</dt>
<dd><p>Enables/Disables use of lossless mode. Default is 0.
</p>
</dd>
<dt> ‘<samp>-compression_level <var>integer</var></samp>’</dt>
<dd><p>For lossy, this is a quality/speed tradeoff. Higher values give better quality
for a given size at the cost of increased encoding time. For lossless, this is
a size/speed tradeoff. Higher values give smaller size at the cost of increased
encoding time. More specifically, it controls the number of extra algorithms
and compression tools used, and varies the combination of these tools. This
maps to the <var>method</var> option in libwebp. The valid range is 0 to 6.
Default is 4.
</p>
</dd>
<dt> ‘<samp>-qscale <var>float</var></samp>’</dt>
<dd><p>For lossy encoding, this controls image quality, 0 to 100. For lossless
encoding, this controls the effort and time spent at compressing more. The
default value is 75. Note that for usage via libavcodec, this option is called
<var>global_quality</var> and must be multiplied by <var>FF_QP2LAMBDA</var>.
</p>
</dd>
<dt> ‘<samp>-preset <var>type</var></samp>’</dt>
<dd><p>Configuration preset. This does some automatic settings based on the general
type of the image.
</p><dl compact="compact">
<dt> ‘<samp>none</samp>’</dt>
<dd><p>Do not use a preset.
</p></dd>
<dt> ‘<samp>default</samp>’</dt>
<dd><p>Use the encoder default.
</p></dd>
<dt> ‘<samp>picture</samp>’</dt>
<dd><p>Digital picture, like portrait, inner shot
</p></dd>
<dt> ‘<samp>photo</samp>’</dt>
<dd><p>Outdoor photograph, with natural lighting
</p></dd>
<dt> ‘<samp>drawing</samp>’</dt>
<dd><p>Hand or line drawing, with high-contrast details
</p></dd>
<dt> ‘<samp>icon</samp>’</dt>
<dd><p>Small-sized colorful images
</p></dd>
<dt> ‘<samp>text</samp>’</dt>
<dd><p>Text-like
</p></dd>
</dl>
</dd>
<dt> ‘<samp>lumi_aq</samp>’</dt>
<dd><p>Enable lumi masking adaptive quantization when set to 1. Default is 0
(disabled).
</p>
</dd>
<dt> ‘<samp>variance_aq</samp>’</dt>
<dd><p>Enable variance adaptive quantization when set to 1. Default is 0
(disabled).
</p>
<p>When combined with ‘<samp>lumi_aq</samp>’, the resulting quality will not
be better than any of the two specified individually. In other
words, the resulting quality will be the worse one of the two
effects.
</p>
</dd>
<dt> ‘<samp>ssim</samp>’</dt>
<dd><p>Set structural similarity (SSIM) displaying method. Possible values:
</p>
<dl compact="compact">
<dt> ‘<samp>off</samp>’</dt>
<dd><p>Disable displaying of SSIM information.
</p>
</dd>
<dt> ‘<samp>avg</samp>’</dt>
<dd><p>Output average SSIM at the end of encoding to stdout. The format of
showing the average SSIM is:
</p>
<table><tr><td> </td><td><pre class="example">Average SSIM: %f
</pre></td></tr></table>
<p>For users who are not familiar with C, %f means a float number, or
a decimal (e.g. 0.939232).
</p>
</dd>
<dt> ‘<samp>frame</samp>’</dt>
<dd><p>Output both per-frame SSIM data during encoding and average SSIM at
the end of encoding to stdout. The format of per-frame information
is:
</p>
<table><tr><td> </td><td><pre class="example"> SSIM: avg: %1.3f min: %1.3f max: %1.3f
</pre></td></tr></table>
<p>For users who are not familiar with C, %1.3f means a float number
rounded to 3 digits after the dot (e.g. 0.932).
</p>
</dd>
</dl>
</dd>
<dt> ‘<samp>ssim_acc</samp>’</dt>
<dd><p>Set SSIM accuracy. Valid options are integers within the range of
0-4, while 0 gives the most accurate result and 4 computes the
fastest.
</p>
</dd>
</dl>
<a name="libx264"></a>
<h2 class="section"><a href="avconv.html#toc-libx264">13.2 libx264</a></h2>
<p>x264 H.264/MPEG-4 AVC encoder wrapper
</p>
<p>x264 supports an impressive number of features, including 8x8 and 4x4 adaptive
spatial transform, adaptive B-frame placement, CAVLC/CABAC entropy coding,
interlacing (MBAFF), lossless mode, psy optimizations for detail retention
(adaptive quantization, psy-RD, psy-trellis).
</p>
<p>The Libav wrapper provides a mapping for most of them using global options
that match those of the encoders and provides private options for the unique
encoder options. Additionally an expert override is provided to directly pass
a list of key=value tuples as accepted by x264_param_parse.
</p>
<a name="Option-Mapping"></a>
<h3 class="subsection"><a href="avconv.html#toc-Option-Mapping">13.2.1 Option Mapping</a></h3>
<p>The following options are supported by the x264 wrapper, the x264-equivalent
options follow the Libav ones.
</p>
<table>
<tr><td>b</td><td>bitrate</td><td>Libav <code>b</code> option is expressed in bits/s, x264 <code>bitrate</code> in kilobits/s.</td></tr>
<tr><td>bf</td><td>bframes</td><td>Maximum number of B-frames.</td></tr>
<tr><td>g</td><td>keyint</td><td>Maximum GOP size.</td></tr>
<tr><td>qmin</td><td>qpmin</td><td>Minimum quantizer scale.</td></tr>
<tr><td>qmax</td><td>qpmax</td><td>Maximum quantizer scale.</td></tr>
<tr><td>qdiff</td><td>qpstep</td><td>Maximum difference between quantizer scales.</td></tr>
<tr><td>qblur</td><td>qblur</td><td>Quantizer curve blur</td></tr>
<tr><td>qcomp</td><td>qcomp</td><td>Quantizer curve compression factor</td></tr>
<tr><td>refs</td><td>ref</td><td>Number of reference frames each P-frame can use. The range is from <var>0-16</var>.</td></tr>
<tr><td>sc_threshold</td><td>scenecut</td><td>Sets the threshold for the scene change detection.</td></tr>
<tr><td>trellis</td><td>trellis</td><td>Performs Trellis quantization to increase efficiency. Enabled by default.</td></tr>
<tr><td>nr</td><td>nr</td><td>Noise reduction.</td></tr>
<tr><td>me_range</td><td>merange</td><td>Maximum range of the motion search in pixels.</td></tr>
<tr><td>me_method</td><td>me</td><td>Full-pixel motion estimation method.</td></tr>
<tr><td>subq</td><td>subme</td><td>Sub-pixel motion estimation method.</td></tr>
<tr><td>b_strategy</td><td>b-adapt</td><td>Adaptive B-frame placement decision algorithm. Use only on first-pass.</td></tr>
<tr><td>keyint_min</td><td>min-keyint</td><td>Minimum GOP size.</td></tr>
<tr><td>coder</td><td>cabac</td><td>Set coder to <code>ac</code> to use CABAC.</td></tr>
<tr><td>cmp</td><td>chroma-me</td><td>Set to <code>chroma</code> to use chroma motion estimation.</td></tr>
<tr><td>threads</td><td>threads</td><td>Number of encoding threads.</td></tr>
<tr><td>thread_type</td><td>sliced_threads</td><td>Set to <code>slice</code> to use sliced threading instead of frame threading.</td></tr>
<tr><td>flags -cgop</td><td>open-gop</td><td>Set <code>-cgop</code> to use recovery points to close GOPs.</td></tr>
<tr><td>rc_init_occupancy</td><td>vbv-init</td><td>Initial buffer occupancy.</td></tr>
</table>
<a name="Private-Options-1"></a>
<h3 class="subsection"><a href="avconv.html#toc-Private-Options-1">13.2.2 Private Options</a></h3>
<dl compact="compact">
<dt> ‘<samp>-preset <var>string</var></samp>’</dt>
<dd><p>Set the encoding preset (cf. x264 –fullhelp).
</p></dd>
<dt> ‘<samp>-tune <var>string</var></samp>’</dt>
<dd><p>Tune the encoding params (cf. x264 –fullhelp).
</p></dd>
<dt> ‘<samp>-profile <var>string</var></samp>’</dt>
<dd><p>Set profile restrictions (cf. x264 –fullhelp).
</p></dd>
<dt> ‘<samp>-fastfirstpass <var>integer</var></samp>’</dt>
<dd><p>Use fast settings when encoding first pass.
</p></dd>
<dt> ‘<samp>-crf <var>float</var></samp>’</dt>
<dd><p>Select the quality for constant quality mode.
</p></dd>
<dt> ‘<samp>-crf_max <var>float</var></samp>’</dt>
<dd><p>In CRF mode, prevents VBV from lowering quality beyond this point.
</p></dd>
<dt> ‘<samp>-qp <var>integer</var></samp>’</dt>
<dd><p>Constant quantization parameter rate control method.
</p></dd>
<dt> ‘<samp>-aq-mode <var>integer</var></samp>’</dt>
<dd><p>AQ method
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>none</samp>’</dt>
<dt> ‘<samp>variance</samp>’</dt>
<dd><p>Variance AQ (complexity mask).
</p></dd>
<dt> ‘<samp>autovariance</samp>’</dt>
<dd><p>Auto-variance AQ (experimental).
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-aq-strength <var>float</var></samp>’</dt>
<dd><p>AQ strength, reduces blocking and blurring in flat and textured areas.
</p></dd>
<dt> ‘<samp>-psy <var>integer</var></samp>’</dt>
<dd><p>Use psychovisual optimizations.
</p></dd>
<dt> ‘<samp>-psy-rd <var>string</var></samp>’</dt>
<dd><p>Strength of psychovisual optimization, in <psy-rd>:<psy-trellis> format.
</p></dd>
<dt> ‘<samp>-rc-lookahead <var>integer</var></samp>’</dt>
<dd><p>Number of frames to look ahead for frametype and ratecontrol.
</p></dd>
<dt> ‘<samp>-weightb <var>integer</var></samp>’</dt>
<dd><p>Weighted prediction for B-frames.
</p></dd>
<dt> ‘<samp>-weightp <var>integer</var></samp>’</dt>
<dd><p>Weighted prediction analysis method.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>none</samp>’</dt>
<dt> ‘<samp>simple</samp>’</dt>
<dt> ‘<samp>smart</samp>’</dt>
</dl>
</dd>
<dt> ‘<samp>-ssim <var>integer</var></samp>’</dt>
<dd><p>Calculate and print SSIM stats.
</p></dd>
<dt> ‘<samp>-intra-refresh <var>integer</var></samp>’</dt>
<dd><p>Use Periodic Intra Refresh instead of IDR frames.
</p></dd>
<dt> ‘<samp>-bluray-compat <var>integer</var></samp>’</dt>
<dd><p>Configure the encoder to be compatible with the bluray standard.
It is a shorthand for setting "bluray-compat=1 force-cfr=1".
</p></dd>
<dt> ‘<samp>-b-bias <var>integer</var></samp>’</dt>
<dd><p>Influences how often B-frames are used.
</p></dd>
<dt> ‘<samp>-b-pyramid <var>integer</var></samp>’</dt>
<dd><p>Keep some B-frames as references.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>none</samp>’</dt>
<dt> ‘<samp>strict</samp>’</dt>
<dd><p>Strictly hierarchical pyramid.
</p></dd>
<dt> ‘<samp>normal</samp>’</dt>
<dd><p>Non-strict (not Blu-ray compatible).
</p></dd>
</dl>
</dd>
<dt> ‘<samp>-mixed-refs <var>integer</var></samp>’</dt>
<dd><p>One reference per partition, as opposed to one reference per macroblock.
</p></dd>
<dt> ‘<samp>-8x8dct <var>integer</var></samp>’</dt>
<dd><p>High profile 8x8 transform.
</p></dd>
<dt> ‘<samp>-fast-pskip <var>integer</var></samp>’</dt>
<dt> ‘<samp>-aud <var>integer</var></samp>’</dt>
<dd><p>Use access unit delimiters.
</p></dd>
<dt> ‘<samp>-mbtree <var>integer</var></samp>’</dt>
<dd><p>Use macroblock tree ratecontrol.
</p></dd>
<dt> ‘<samp>-deblock <var>string</var></samp>’</dt>
<dd><p>Loop filter parameters, in <alpha:beta> form.
</p></dd>
<dt> ‘<samp>-cplxblur <var>float</var></samp>’</dt>
<dd><p>Reduce fluctuations in QP (before curve compression).
</p></dd>
<dt> ‘<samp>-partitions <var>string</var></samp>’</dt>
<dd><p>A comma-separated list of partitions to consider, possible values: p8x8, p4x4, b8x8, i8x8, i4x4, none, all.
</p></dd>
<dt> ‘<samp>-direct-pred <var>integer</var></samp>’</dt>
<dd><p>Direct MV prediction mode
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>none</samp>’</dt>
<dt> ‘<samp>spatial</samp>’</dt>
<dt> ‘<samp>temporal</samp>’</dt>
<dt> ‘<samp>auto</samp>’</dt>
</dl>
</dd>
<dt> ‘<samp>-slice-max-size <var>integer</var></samp>’</dt>
<dd><p>Limit the size of each slice in bytes.
</p></dd>
<dt> ‘<samp>-stats <var>string</var></samp>’</dt>
<dd><p>Filename for 2 pass stats.
</p></dd>
<dt> ‘<samp>-nal-hrd <var>integer</var></samp>’</dt>
<dd><p>Signal HRD information (requires vbv-bufsize; cbr not allowed in .mp4).
</p>
<p>Possible values:
</p><dl compact="compact">
<dt> ‘<samp>none</samp>’</dt>
<dt> ‘<samp>vbr</samp>’</dt>
<dt> ‘<samp>cbr</samp>’</dt>
</dl>
</dd>
<dt> ‘<samp>-x264-params <var>string</var></samp>’</dt>
<dd><p>Override the x264 configuration using a :-separated list of key=value parameters.
</p><table><tr><td> </td><td><pre class="example">-x264-params level=30:bframes=0:weightp=0:cabac=0:ref=1:vbv-maxrate=768:vbv-bufsize=2000:analyse=all:me=umh:no-fast-pskip=1:subq=6:8x8dct=0:trellis=0
</pre></td></tr></table>
</dd>
</dl>
<p>Encoding avpresets for common usages are provided so they can be used with the
general presets system (e.g. passing the <code>-pre</code> option).
</p>
<a name="ProRes"></a>
<h2 class="section"><a href="avconv.html#toc-ProRes">13.3 ProRes</a></h2>
<p>Apple ProRes encoder.
</p>
<a name="Private-Options"></a>
<h3 class="subsection"><a href="avconv.html#toc-Private-Options">13.3.1 Private Options</a></h3>
<dl compact="compact">
<dt> ‘<samp>profile <var>integer</var></samp>’</dt>
<dd><p>Select the ProRes profile to encode
</p><dl compact="compact">
<dt> ‘<samp>proxy</samp>’</dt>
<dt> ‘<samp>lt</samp>’</dt>
<dt> ‘<samp>standard</samp>’</dt>
<dt> ‘<samp>hq</samp>’</dt>
<dt> ‘<samp>4444</samp>’</dt>
</dl>
</dd>
<dt> ‘<samp>quant_mat <var>integer</var></samp>’</dt>
<dd><p>Select quantization matrix.
</p><dl compact="compact">
<dt> ‘<samp>auto</samp>’</dt>
<dt> ‘<samp>default</samp>’</dt>
<dt> ‘<samp>proxy</samp>’</dt>
<dt> ‘<samp>lt</samp>’</dt>
<dt> ‘<samp>standard</samp>’</dt>
<dt> ‘<samp>hq</samp>’</dt>
</dl>
<p>If set to <var>auto</var>, the matrix matching the profile will be picked.
If not set, the matrix providing the highest quality, <var>default</var>, will be
picked.
</p>
</dd>
<dt> ‘<samp>bits_per_mb <var>integer</var></samp>’</dt>
<dd><p>How many bits to allot for coding one macroblock. Different profiles use
between 200 and 2400 bits per macroblock, the maximum is 8000.
</p>
</dd>
<dt> ‘<samp>mbs_per_slice <var>integer</var></samp>’</dt>
<dd><p>Number of macroblocks in each slice (1-8); the default value (8)
should be good in almost all situations.
</p>
</dd>
<dt> ‘<samp>vendor <var>string</var></samp>’</dt>
<dd><p>Override the 4-byte vendor ID.
A custom vendor ID like <var>apl0</var> would claim the stream was produced by
the Apple encoder.
</p>
</dd>
<dt> ‘<samp>alpha_bits <var>integer</var></samp>’</dt>
<dd><p>Specify number of bits for alpha component.
Possible values are <var>0</var>, <var>8</var> and <var>16</var>.
Use <var>0</var> to disable alpha plane coding.
</p>
</dd>
</dl>
<a name="Speed-considerations"></a>
<h3 class="subsection"><a href="avconv.html#toc-Speed-considerations">13.3.2 Speed considerations</a></h3>
<p>In the default mode of operation the encoder has to honor frame constraints
(i.e. not produc frames with size bigger than requested) while still making
output picture as good as possible.
A frame containing a lot of small details is harder to compress and the encoder
would spend more time searching for appropriate quantizers for each slice.
</p>
<p>Setting a higher ‘<samp>bits_per_mb</samp>’ limit will improve the speed.
</p>
<p>For the fastest encoding speed set the ‘<samp>qscale</samp>’ parameter (4 is the
recommended value) and do not set a size constraint.
</p>
<a name="Demuxers"></a>
<h1 class="chapter"><a href="avconv.html#toc-Demuxers">14. Demuxers</a></h1>
<p>Demuxers are configured elements in Libav which allow to read the
multimedia streams from a particular type of file.
</p>
<p>When you configure your Libav build, all the supported demuxers
are enabled by default. You can list all available ones using the
configure option "–list-demuxers".
</p>
<p>You can disable all the demuxers using the configure option
"–disable-demuxers", and selectively enable a single demuxer with
the option "–enable-demuxer=<var>DEMUXER</var>", or disable it
with the option "–disable-demuxer=<var>DEMUXER</var>".
</p>
<p>The option "-formats" of the av* tools will display the list of
enabled demuxers.
</p>
<p>The description of some of the currently available demuxers follows.
</p>
<a name="image2-1"></a>
<h2 class="section"><a href="avconv.html#toc-image2-1">14.1 image2</a></h2>
<p>Image file demuxer.
</p>
<p>This demuxer reads from a list of image files specified by a pattern.
</p>
<p>The pattern may contain the string "%d" or "%0<var>N</var>d", which
specifies the position of the characters representing a sequential
number in each filename matched by the pattern. If the form
"%d0<var>N</var>d" is used, the string representing the number in each
filename is 0-padded and <var>N</var> is the total number of 0-padded
digits representing the number. The literal character ’%’ can be
specified in the pattern with the string "%%".
</p>
<p>If the pattern contains "%d" or "%0<var>N</var>d", the first filename of
the file list specified by the pattern must contain a number
inclusively contained between 0 and 4, all the following numbers must
be sequential. This limitation may be hopefully fixed.
</p>
<p>The pattern may contain a suffix which is used to automatically
determine the format of the images contained in the files.
</p>
<p>For example the pattern "img-%03d.bmp" will match a sequence of
filenames of the form ‘<tt>img-001.bmp</tt>’, ‘<tt>img-002.bmp</tt>’, ...,
‘<tt>img-010.bmp</tt>’, etc.; the pattern "i%%m%%g-%d.jpg" will match a
sequence of filenames of the form ‘<tt>i%m%g-1.jpg</tt>’,
‘<tt>i%m%g-2.jpg</tt>’, ..., ‘<tt>i%m%g-10.jpg</tt>’, etc.
</p>
<p>The size, the pixel format, and the format of each image must be the
same for all the files in the sequence.
</p>
<p>The following example shows how to use <code>avconv</code> for creating a
video from the images in the file sequence ‘<tt>img-001.jpeg</tt>’,
‘<tt>img-002.jpeg</tt>’, ..., assuming an input framerate of 10 frames per
second:
</p><table><tr><td> </td><td><pre class="example">avconv -i 'img-%03d.jpeg' -r 10 out.mkv
</pre></td></tr></table>
<p>Note that the pattern must not necessarily contain "%d" or
"%0<var>N</var>d", for example to convert a single image file
‘<tt>img.jpeg</tt>’ you can employ the command:
</p><table><tr><td> </td><td><pre class="example">avconv -i img.jpeg img.png
</pre></td></tr></table>
<dl compact="compact">
<dt> ‘<samp>-pixel_format <var>format</var></samp>’</dt>
<dd><p>Set the pixel format (for raw image)
</p></dd>
<dt> ‘<samp>-video_size <var>size</var></samp>’</dt>
<dd><p>Set the frame size (for raw image)
</p></dd>
<dt> ‘<samp>-framerate <var>rate</var></samp>’</dt>
<dd><p>Set the frame rate
</p></dd>
<dt> ‘<samp>-loop <var>bool</var></samp>’</dt>
<dd><p>Loop over the images
</p></dd>
<dt> ‘<samp>-start_number <var>start</var></samp>’</dt>
<dd><p>Specify the first number in the sequence
</p></dd>
</dl>
<a name="applehttp"></a>
<h2 class="section"><a href="avconv.html#toc-applehttp">14.2 applehttp</a></h2>
<p>Apple HTTP Live Streaming demuxer.
</p>
<p>This demuxer presents all AVStreams from all variant streams.
The id field is set to the bitrate variant index number. By setting
the discard flags on AVStreams (by pressing ’a’ or ’v’ in avplay),
the caller can decide which variant streams to actually receive.
The total bitrate of the variant that the stream belongs to is
available in a metadata key named "variant_bitrate".
</p>
<a name="flv"></a>
<h2 class="section"><a href="avconv.html#toc-flv">14.3 flv</a></h2>
<p>Adobe Flash Video Format demuxer.
</p>
<p>This demuxer is used to demux FLV files and RTMP network streams.
</p>
<dl compact="compact">
<dt> ‘<samp>-flv_metadata <var>bool</var></samp>’</dt>
<dd><p>Allocate the streams according to the onMetaData array content.
</p></dd>
</dl>
<a name="asf"></a>
<h2 class="section"><a href="avconv.html#toc-asf">14.4 asf</a></h2>
<p>Advanced Systems Format demuxer.
</p>
<p>This demuxer is used to demux ASF files and MMS network streams.
</p>
<dl compact="compact">
<dt> ‘<samp>-no_resync_search <var>bool</var></samp>’</dt>
<dd><p>Do not try to resynchronize by looking for a certain optional start code.
</p></dd>
</dl>
<a name="Muxers"></a>
<h1 class="chapter"><a href="avconv.html#toc-Muxers">15. Muxers</a></h1>
<p>Muxers are configured elements in Libav which allow writing
multimedia streams to a particular type of file.
</p>
<p>When you configure your Libav build, all the supported muxers
are enabled by default. You can list all available muxers using the
configure option <code>--list-muxers</code>.
</p>
<p>You can disable all the muxers with the configure option
<code>--disable-muxers</code> and selectively enable / disable single muxers
with the options <code>--enable-muxer=<var>MUXER</var></code> /
<code>--disable-muxer=<var>MUXER</var></code>.
</p>
<p>The option <code>-formats</code> of the av* tools will display the list of
enabled muxers.
</p>
<p>A description of some of the currently available muxers follows.
</p>
<p><a name="crc"></a>
</p><a name="crc-1"></a>
<h2 class="section"><a href="avconv.html#toc-crc-1">15.1 crc</a></h2>
<p>CRC (Cyclic Redundancy Check) testing format.
</p>
<p>This muxer computes and prints the Adler-32 CRC of all the input audio
and video frames. By default audio frames are converted to signed
16-bit raw audio and video frames to raw video before computing the
CRC.
</p>
<p>The output of the muxer consists of a single line of the form:
CRC=0x<var>CRC</var>, where <var>CRC</var> is a hexadecimal number 0-padded to
8 digits containing the CRC for all the decoded input frames.
</p>
<p>For example to compute the CRC of the input, and store it in the file
‘<tt>out.crc</tt>’:
</p><table><tr><td> </td><td><pre class="example">avconv -i INPUT -f crc out.crc
</pre></td></tr></table>
<p>You can print the CRC to stdout with the command:
</p><table><tr><td> </td><td><pre class="example">avconv -i INPUT -f crc -
</pre></td></tr></table>
<p>You can select the output format of each frame with <code>avconv</code> by
specifying the audio and video codec and format. For example to
compute the CRC of the input audio converted to PCM unsigned 8-bit
and the input video converted to MPEG-2 video, use the command:
</p><table><tr><td> </td><td><pre class="example">avconv -i INPUT -c:a pcm_u8 -c:v mpeg2video -f crc -
</pre></td></tr></table>
<p>See also the <a href="#framecrc">framecrc</a> muxer.
</p>
<p><a name="framecrc"></a>
</p><a name="framecrc-1"></a>
<h2 class="section"><a href="avconv.html#toc-framecrc-1">15.2 framecrc</a></h2>
<p>Per-frame CRC (Cyclic Redundancy Check) testing format.
</p>
<p>This muxer computes and prints the Adler-32 CRC for each decoded audio
and video frame. By default audio frames are converted to signed
16-bit raw audio and video frames to raw video before computing the
CRC.
</p>
<p>The output of the muxer consists of a line for each audio and video
frame of the form: <var>stream_index</var>, <var>frame_dts</var>,
<var>frame_size</var>, 0x<var>CRC</var>, where <var>CRC</var> is a hexadecimal
number 0-padded to 8 digits containing the CRC of the decoded frame.
</p>
<p>For example to compute the CRC of each decoded frame in the input, and
store it in the file ‘<tt>out.crc</tt>’:
</p><table><tr><td> </td><td><pre class="example">avconv -i INPUT -f framecrc out.crc
</pre></td></tr></table>
<p>You can print the CRC of each decoded frame to stdout with the command:
</p><table><tr><td> </td><td><pre class="example">avconv -i INPUT -f framecrc -
</pre></td></tr></table>
<p>You can select the output format of each frame with <code>avconv</code> by
specifying the audio and video codec and format. For example, to
compute the CRC of each decoded input audio frame converted to PCM
unsigned 8-bit and of each decoded input video frame converted to
MPEG-2 video, use the command:
</p><table><tr><td> </td><td><pre class="example">avconv -i INPUT -c:a pcm_u8 -c:v mpeg2video -f framecrc -
</pre></td></tr></table>
<p>See also the <a href="#crc">crc</a> muxer.
</p>
<p><a name="hls"></a>
</p><a name="hls-1"></a>
<h2 class="section"><a href="avconv.html#toc-hls-1">15.3 hls</a></h2>
<p>Apple HTTP Live Streaming muxer that segments MPEG-TS according to
the HTTP Live Streaming specification.
</p>
<p>It creates a playlist file and numbered segment files. The output
filename specifies the playlist filename; the segment filenames
receive the same basename as the playlist, a sequential number and
a .ts extension.
</p>
<table><tr><td> </td><td><pre class="example">avconv -i in.nut out.m3u8
</pre></td></tr></table>
<dl compact="compact">
<dt> ‘<samp>-hls_time <var>seconds</var></samp>’</dt>
<dd><p>Set the segment length in seconds.
</p></dd>
<dt> ‘<samp>-hls_list_size <var>size</var></samp>’</dt>
<dd><p>Set the maximum number of playlist entries.
</p></dd>
<dt> ‘<samp>-hls_wrap <var>wrap</var></samp>’</dt>
<dd><p>Set the number after which index wraps.
</p></dd>
<dt> ‘<samp>-start_number <var>number</var></samp>’</dt>
<dd><p>Start the sequence from <var>number</var>.
</p></dd>
<dt> ‘<samp>-hls_base_url <var>baseurl</var></samp>’</dt>
<dd><p>Append <var>baseurl</var> to every entry in the playlist.
Useful to generate playlists with absolute paths.
</p></dd>
</dl>
<p><a name="image2"></a>
</p><a name="image2-2"></a>
<h2 class="section"><a href="avconv.html#toc-image2-2">15.4 image2</a></h2>
<p>Image file muxer.
</p>
<p>The image file muxer writes video frames to image files.
</p>
<p>The output filenames are specified by a pattern, which can be used to
produce sequentially numbered series of files.
The pattern may contain the string "%d" or "%0<var>N</var>d", this string
specifies the position of the characters representing a numbering in
the filenames. If the form "%0<var>N</var>d" is used, the string
representing the number in each filename is 0-padded to <var>N</var>
digits. The literal character ’%’ can be specified in the pattern with
the string "%%".
</p>
<p>If the pattern contains "%d" or "%0<var>N</var>d", the first filename of
the file list specified will contain the number 1, all the following
numbers will be sequential.
</p>
<p>The pattern may contain a suffix which is used to automatically
determine the format of the image files to write.
</p>
<p>For example the pattern "img-%03d.bmp" will specify a sequence of
filenames of the form ‘<tt>img-001.bmp</tt>’, ‘<tt>img-002.bmp</tt>’, ...,
‘<tt>img-010.bmp</tt>’, etc.
The pattern "img%%-%d.jpg" will specify a sequence of filenames of the
form ‘<tt>img%-1.jpg</tt>’, ‘<tt>img%-2.jpg</tt>’, ..., ‘<tt>img%-10.jpg</tt>’,
etc.
</p>
<p>The following example shows how to use <code>avconv</code> for creating a
sequence of files ‘<tt>img-001.jpeg</tt>’, ‘<tt>img-002.jpeg</tt>’, ...,
taking one image every second from the input video:
</p><table><tr><td> </td><td><pre class="example">avconv -i in.avi -vsync 1 -r 1 -f image2 'img-%03d.jpeg'
</pre></td></tr></table>
<p>Note that with <code>avconv</code>, if the format is not specified with the
<code>-f</code> option and the output filename specifies an image file
format, the image2 muxer is automatically selected, so the previous
command can be written as:
</p><table><tr><td> </td><td><pre class="example">avconv -i in.avi -vsync 1 -r 1 'img-%03d.jpeg'
</pre></td></tr></table>
<p>Note also that the pattern must not necessarily contain "%d" or
"%0<var>N</var>d", for example to create a single image file
‘<tt>img.jpeg</tt>’ from the input video you can employ the command:
</p><table><tr><td> </td><td><pre class="example">avconv -i in.avi -f image2 -frames:v 1 img.jpeg
</pre></td></tr></table>
<dl compact="compact">
<dt> ‘<samp>-start_number <var>number</var></samp>’</dt>
<dd><p>Start the sequence from <var>number</var>.
</p>
</dd>
<dt> ‘<samp>-update <var>number</var></samp>’</dt>
<dd><p>If <var>number</var> is nonzero, the filename will always be interpreted as just a
filename, not a pattern, and this file will be continuously overwritten with new
images.
</p>
</dd>
</dl>
<a name="matroska"></a>
<h2 class="section"><a href="avconv.html#toc-matroska">15.5 matroska</a></h2>
<p>Matroska container muxer.
</p>
<p>This muxer implements the matroska and webm container specs.
</p>
<p>The recognized metadata settings in this muxer are:
</p>
<dl compact="compact">
<dt> ‘<samp>title=<var>title name</var></samp>’</dt>
<dd><p>Name provided to a single track
</p></dd>
</dl>
<dl compact="compact">
<dt> ‘<samp>language=<var>language name</var></samp>’</dt>
<dd><p>Specifies the language of the track in the Matroska languages form
</p></dd>
</dl>
<dl compact="compact">
<dt> ‘<samp>STEREO_MODE=<var>mode</var></samp>’</dt>
<dd><p>Stereo 3D video layout of two views in a single video track
</p><dl compact="compact">
<dt> ‘<samp>mono</samp>’</dt>
<dd><p>video is not stereo
</p></dd>
<dt> ‘<samp>left_right</samp>’</dt>
<dd><p>Both views are arranged side by side, Left-eye view is on the left
</p></dd>
<dt> ‘<samp>bottom_top</samp>’</dt>
<dd><p>Both views are arranged in top-bottom orientation, Left-eye view is at bottom
</p></dd>
<dt> ‘<samp>top_bottom</samp>’</dt>
<dd><p>Both views are arranged in top-bottom orientation, Left-eye view is on top
</p></dd>
<dt> ‘<samp>checkerboard_rl</samp>’</dt>
<dd><p>Each view is arranged in a checkerboard interleaved pattern, Left-eye view being first
</p></dd>
<dt> ‘<samp>checkerboard_lr</samp>’</dt>
<dd><p>Each view is arranged in a checkerboard interleaved pattern, Right-eye view being first
</p></dd>
<dt> ‘<samp>row_interleaved_rl</samp>’</dt>
<dd><p>Each view is constituted by a row based interleaving, Right-eye view is first row
</p></dd>
<dt> ‘<samp>row_interleaved_lr</samp>’</dt>
<dd><p>Each view is constituted by a row based interleaving, Left-eye view is first row
</p></dd>
<dt> ‘<samp>col_interleaved_rl</samp>’</dt>
<dd><p>Both views are arranged in a column based interleaving manner, Right-eye view is first column
</p></dd>
<dt> ‘<samp>col_interleaved_lr</samp>’</dt>
<dd><p>Both views are arranged in a column based interleaving manner, Left-eye view is first column
</p></dd>
<dt> ‘<samp>anaglyph_cyan_red</samp>’</dt>
<dd><p>All frames are in anaglyph format viewable through red-cyan filters
</p></dd>
<dt> ‘<samp>right_left</samp>’</dt>
<dd><p>Both views are arranged side by side, Right-eye view is on the left
</p></dd>
<dt> ‘<samp>anaglyph_green_magenta</samp>’</dt>
<dd><p>All frames are in anaglyph format viewable through green-magenta filters
</p></dd>
<dt> ‘<samp>block_lr</samp>’</dt>
<dd><p>Both eyes laced in one Block, Left-eye view is first
</p></dd>
<dt> ‘<samp>block_rl</samp>’</dt>
<dd><p>Both eyes laced in one Block, Right-eye view is first
</p></dd>
</dl>
</dd>
</dl>
<p>For example a 3D WebM clip can be created using the following command line:
</p><table><tr><td> </td><td><pre class="example">avconv -i sample_left_right_clip.mpg -an -c:v libvpx -metadata STEREO_MODE=left_right -y stereo_clip.webm
</pre></td></tr></table>
<p>This muxer supports the following options:
</p>
<dl compact="compact">
<dt> ‘<samp>reserve_index_space</samp>’</dt>
<dd><p>By default, this muxer writes the index for seeking (called cues in Matroska
terms) at the end of the file, because it cannot know in advance how much space
to leave for the index at the beginning of the file. However for some use cases
– e.g. streaming where seeking is possible but slow – it is useful to put the
index at the beginning of the file.
</p>
<p>If this option is set to a non-zero value, the muxer will reserve a given amount
of space in the file header and then try to write the cues there when the muxing
finishes. If the available space does not suffice, muxing will fail. A safe size
for most use cases should be about 50kB per hour of video.
</p>
<p>Note that cues are only written if the output is seekable and this option will
have no effect if it is not.
</p>
</dd>
</dl>
<a name="mov_002c-mp4_002c-ismv"></a>
<h2 class="section"><a href="avconv.html#toc-mov_002c-mp4_002c-ismv">15.6 mov, mp4, ismv</a></h2>
<p>The mov/mp4/ismv muxer supports fragmentation. Normally, a MOV/MP4
file has all the metadata about all packets stored in one location
(written at the end of the file, it can be moved to the start for
better playback using the <code>qt-faststart</code> tool). A fragmented
file consists of a number of fragments, where packets and metadata
about these packets are stored together. Writing a fragmented
file has the advantage that the file is decodable even if the
writing is interrupted (while a normal MOV/MP4 is undecodable if
it is not properly finished), and it requires less memory when writing
very long files (since writing normal MOV/MP4 files stores info about
every single packet in memory until the file is closed). The downside
is that it is less compatible with other applications.
</p>
<p>Fragmentation is enabled by setting one of the AVOptions that define
how to cut the file into fragments:
</p>
<dl compact="compact">
<dt> ‘<samp>-movflags frag_keyframe</samp>’</dt>
<dd><p>Start a new fragment at each video keyframe.
</p></dd>
<dt> ‘<samp>-frag_duration <var>duration</var></samp>’</dt>
<dd><p>Create fragments that are <var>duration</var> microseconds long.
</p></dd>
<dt> ‘<samp>-frag_size <var>size</var></samp>’</dt>
<dd><p>Create fragments that contain up to <var>size</var> bytes of payload data.
</p></dd>
<dt> ‘<samp>-movflags frag_custom</samp>’</dt>
<dd><p>Allow the caller to manually choose when to cut fragments, by
calling <code>av_write_frame(ctx, NULL)</code> to write a fragment with
the packets written so far. (This is only useful with other
applications integrating libavformat, not from <code>avconv</code>.)
</p></dd>
<dt> ‘<samp>-min_frag_duration <var>duration</var></samp>’</dt>
<dd><p>Don’t create fragments that are shorter than <var>duration</var> microseconds long.
</p></dd>
</dl>
<p>If more than one condition is specified, fragments are cut when
one of the specified conditions is fulfilled. The exception to this is
<code>-min_frag_duration</code>, which has to be fulfilled for any of the other
conditions to apply.
</p>
<p>Additionally, the way the output file is written can be adjusted
through a few other options:
</p>
<dl compact="compact">
<dt> ‘<samp>-movflags empty_moov</samp>’</dt>
<dd><p>Write an initial moov atom directly at the start of the file, without
describing any samples in it. Generally, an mdat/moov pair is written
at the start of the file, as a normal MOV/MP4 file, containing only
a short portion of the file. With this option set, there is no initial
mdat atom, and the moov atom only describes the tracks but has
a zero duration.
</p>
<p>Files written with this option set do not work in QuickTime.
This option is implicitly set when writing ismv (Smooth Streaming) files.
</p></dd>
<dt> ‘<samp>-movflags separate_moof</samp>’</dt>
<dd><p>Write a separate moof (movie fragment) atom for each track. Normally,
packets for all tracks are written in a moof atom (which is slightly
more efficient), but with this option set, the muxer writes one moof/mdat
pair for each track, making it easier to separate tracks.
</p>
<p>This option is implicitly set when writing ismv (Smooth Streaming) files.
</p></dd>
<dt> ‘<samp>-movflags faststart</samp>’</dt>
<dd><p>Run a second pass moving the index (moov atom) to the beginning of the file.
This operation can take a while, and will not work in various situations such
as fragmented output, thus it is not enabled by default.
</p></dd>
<dt> ‘<samp>-movflags disable_chpl</samp>’</dt>
<dd><p>Disable Nero chapter markers (chpl atom). Normally, both Nero chapters
and a QuickTime chapter track are written to the file. With this option
set, only the QuickTime chapter track will be written. Nero chapters can
cause failures when the file is reprocessed with certain tagging programs.
</p></dd>
</dl>
<p>Smooth Streaming content can be pushed in real time to a publishing
point on IIS with this muxer. Example:
</p><table><tr><td> </td><td><pre class="example">avconv -re <var><normal input/transcoding options></var> -movflags isml+frag_keyframe -f ismv http://server/publishingpoint.isml/Streams(Encoder1)
</pre></td></tr></table>
<a name="mp3"></a>
<h2 class="section"><a href="avconv.html#toc-mp3">15.7 mp3</a></h2>
<p>The MP3 muxer writes a raw MP3 stream with an ID3v2 header at the beginning and
optionally an ID3v1 tag at the end. ID3v2.3 and ID3v2.4 are supported, the
<code>id3v2_version</code> option controls which one is used. Setting
<code>id3v2_version</code> to 0 will disable the ID3v2 header completely. The legacy
ID3v1 tag is not written by default, but may be enabled with the
<code>write_id3v1</code> option.
</p>
<p>The muxer may also write a Xing frame at the beginning, which contains the
number of frames in the file. It is useful for computing duration of VBR files.
The Xing frame is written if the output stream is seekable and if the
<code>write_xing</code> option is set to 1 (the default).
</p>
<p>The muxer supports writing ID3v2 attached pictures (APIC frames). The pictures
are supplied to the muxer in form of a video stream with a single packet. There
can be any number of those streams, each will correspond to a single APIC frame.
The stream metadata tags <var>title</var> and <var>comment</var> map to APIC
<var>description</var> and <var>picture type</var> respectively. See
<a href="http://id3.org/id3v2.4.0-frames">http://id3.org/id3v2.4.0-frames</a> for allowed picture types.
</p>
<p>Note that the APIC frames must be written at the beginning, so the muxer will
buffer the audio frames until it gets all the pictures. It is therefore advised
to provide the pictures as soon as possible to avoid excessive buffering.
</p>
<p>Examples:
</p>
<p>Write an mp3 with an ID3v2.3 header and an ID3v1 footer:
</p><table><tr><td> </td><td><pre class="example">avconv -i INPUT -id3v2_version 3 -write_id3v1 1 out.mp3
</pre></td></tr></table>
<p>Attach a picture to an mp3:
</p><table><tr><td> </td><td><pre class="example">avconv -i input.mp3 -i cover.png -c copy -metadata:s:v title="Album cover"
-metadata:s:v comment="Cover (Front)" out.mp3
</pre></td></tr></table>
<p>Write a "clean" MP3 without any extra features:
</p><table><tr><td> </td><td><pre class="example">avconv -i input.wav -write_xing 0 -id3v2_version 0 out.mp3
</pre></td></tr></table>
<a name="mpegts"></a>
<h2 class="section"><a href="avconv.html#toc-mpegts">15.8 mpegts</a></h2>
<p>MPEG transport stream muxer.
</p>
<p>This muxer implements ISO 13818-1 and part of ETSI EN 300 468.
</p>
<p>The muxer options are:
</p>
<dl compact="compact">
<dt> ‘<samp>-mpegts_original_network_id <var>number</var></samp>’</dt>
<dd><p>Set the original_network_id (default 0x0001). This is unique identifier
of a network in DVB. Its main use is in the unique identification of a
service through the path Original_Network_ID, Transport_Stream_ID.
</p></dd>
<dt> ‘<samp>-mpegts_transport_stream_id <var>number</var></samp>’</dt>
<dd><p>Set the transport_stream_id (default 0x0001). This identifies a
transponder in DVB.
</p></dd>
<dt> ‘<samp>-mpegts_service_id <var>number</var></samp>’</dt>
<dd><p>Set the service_id (default 0x0001) also known as program in DVB.
</p></dd>
<dt> ‘<samp>-mpegts_pmt_start_pid <var>number</var></samp>’</dt>
<dd><p>Set the first PID for PMT (default 0x1000, max 0x1f00).
</p></dd>
<dt> ‘<samp>-mpegts_start_pid <var>number</var></samp>’</dt>
<dd><p>Set the first PID for data packets (default 0x0100, max 0x0f00).
</p></dd>
<dt> ‘<samp>-muxrate <var>number</var></samp>’</dt>
<dd><p>Set a constant muxrate (default VBR).
</p></dd>
<dt> ‘<samp>-pcr_period <var>numer</var></samp>’</dt>
<dd><p>Override the default PCR retransmission time (default 20ms), ignored
if variable muxrate is selected.
</p></dd>
</dl>
<p>The recognized metadata settings in mpegts muxer are <code>service_provider</code>
and <code>service_name</code>. If they are not set the default for
<code>service_provider</code> is "Libav" and the default for
<code>service_name</code> is "Service01".
</p>
<table><tr><td> </td><td><pre class="example">avconv -i file.mpg -c copy \
-mpegts_original_network_id 0x1122 \
-mpegts_transport_stream_id 0x3344 \
-mpegts_service_id 0x5566 \
-mpegts_pmt_start_pid 0x1500 \
-mpegts_start_pid 0x150 \
-metadata service_provider="Some provider" \
-metadata service_name="Some Channel" \
-y out.ts
</pre></td></tr></table>
<a name="null"></a>
<h2 class="section"><a href="avconv.html#toc-null">15.9 null</a></h2>
<p>Null muxer.
</p>
<p>This muxer does not generate any output file, it is mainly useful for
testing or benchmarking purposes.
</p>
<p>For example to benchmark decoding with <code>avconv</code> you can use the
command:
</p><table><tr><td> </td><td><pre class="example">avconv -benchmark -i INPUT -f null out.null
</pre></td></tr></table>
<p>Note that the above command does not read or write the ‘<tt>out.null</tt>’
file, but specifying the output file is required by the <code>avconv</code>
syntax.
</p>
<p>Alternatively you can write the command as:
</p><table><tr><td> </td><td><pre class="example">avconv -benchmark -i INPUT -f null -
</pre></td></tr></table>
<a name="nut"></a>
<h2 class="section"><a href="avconv.html#toc-nut">15.10 nut</a></h2>
<dl compact="compact">
<dt> ‘<samp>-syncpoints <var>flags</var></samp>’</dt>
<dd><p>Change the syncpoint usage in nut:
</p><dl compact="compact">
<dt> ‘<samp><var>default</var> use the normal low-overhead seeking aids.</samp>’</dt>
<dt> ‘<samp><var>none</var> do not use the syncpoints at all, reducing the overhead but making the stream non-seekable;</samp>’</dt>
<dt> ‘<samp><var>timestamped</var> extend the syncpoint with a wallclock field.</samp>’</dt>
</dl>
<p>The <var>none</var> and <var>timestamped</var> flags are experimental.
</p></dd>
</dl>
<table><tr><td> </td><td><pre class="example">avconv -i INPUT -f_strict experimental -syncpoints none - | processor
</pre></td></tr></table>
<a name="ogg"></a>
<h2 class="section"><a href="avconv.html#toc-ogg">15.11 ogg</a></h2>
<p>Ogg container muxer.
</p>
<dl compact="compact">
<dt> ‘<samp>-page_duration <var>duration</var></samp>’</dt>
<dd><p>Preferred page duration, in microseconds. The muxer will attempt to create
pages that are approximately <var>duration</var> microseconds long. This allows the
user to compromise between seek granularity and container overhead. The default
is 1 second. A value of 0 will fill all segments, making pages as large as
possible. A value of 1 will effectively use 1 packet-per-page in most
situations, giving a small seek granularity at the cost of additional container
overhead.
</p></dd>
</dl>
<a name="segment"></a>
<h2 class="section"><a href="avconv.html#toc-segment">15.12 segment</a></h2>
<p>Basic stream segmenter.
</p>
<p>The segmenter muxer outputs streams to a number of separate files of nearly
fixed duration. Output filename pattern can be set in a fashion similar to
<a href="#image2">image2</a>.
</p>
<p>Every segment starts with a video keyframe, if a video stream is present.
The segment muxer works best with a single constant frame rate video.
</p>
<p>Optionally it can generate a flat list of the created segments, one segment
per line.
</p>
<dl compact="compact">
<dt> ‘<samp>segment_format <var>format</var></samp>’</dt>
<dd><p>Override the inner container format, by default it is guessed by the filename
extension.
</p></dd>
<dt> ‘<samp>segment_time <var>t</var></samp>’</dt>
<dd><p>Set segment duration to <var>t</var> seconds.
</p></dd>
<dt> ‘<samp>segment_list <var>name</var></samp>’</dt>
<dd><p>Generate also a listfile named <var>name</var>.
</p></dd>
<dt> ‘<samp>segment_list_type <var>type</var></samp>’</dt>
<dd><p>Select the listing format.
</p><dl compact="compact">
<dt> ‘<samp><var>flat</var> use a simple flat list of entries.</samp>’</dt>
<dt> ‘<samp><var>hls</var> use a m3u8-like structure.</samp>’</dt>
</dl>
</dd>
<dt> ‘<samp>segment_list_size <var>size</var></samp>’</dt>
<dd><p>Overwrite the listfile once it reaches <var>size</var> entries.
</p></dd>
<dt> ‘<samp>segment_list_entry_prefix <var>prefix</var></samp>’</dt>
<dd><p>Prepend <var>prefix</var> to each entry. Useful to generate absolute paths.
</p></dd>
<dt> ‘<samp>segment_wrap <var>limit</var></samp>’</dt>
<dd><p>Wrap around segment index once it reaches <var>limit</var>.
</p></dd>
</dl>
<table><tr><td> </td><td><pre class="example">avconv -i in.mkv -c copy -map 0 -f segment -list out.list out%03d.nut
</pre></td></tr></table>
<a name="Input-Devices"></a>
<h1 class="chapter"><a href="avconv.html#toc-Input-Devices">16. Input Devices</a></h1>
<p>Input devices are configured elements in Libav which allow to access
the data coming from a multimedia device attached to your system.
</p>
<p>When you configure your Libav build, all the supported input devices
are enabled by default. You can list all available ones using the
configure option "–list-indevs".
</p>
<p>You can disable all the input devices using the configure option
"–disable-indevs", and selectively enable an input device using the
option "–enable-indev=<var>INDEV</var>", or you can disable a particular
input device using the option "–disable-indev=<var>INDEV</var>".
</p>
<p>The option "-formats" of the av* tools will display the list of
supported input devices (amongst the demuxers).
</p>
<p>A description of the currently available input devices follows.
</p>
<a name="alsa-1"></a>
<h2 class="section"><a href="avconv.html#toc-alsa-1">16.1 alsa</a></h2>
<p>ALSA (Advanced Linux Sound Architecture) input device.
</p>
<p>To enable this input device during configuration you need libasound
installed on your system.
</p>
<p>This device allows capturing from an ALSA device. The name of the
device to capture has to be an ALSA card identifier.
</p>
<p>An ALSA identifier has the syntax:
</p><table><tr><td> </td><td><pre class="example">hw:<var>CARD</var>[,<var>DEV</var>[,<var>SUBDEV</var>]]
</pre></td></tr></table>
<p>where the <var>DEV</var> and <var>SUBDEV</var> components are optional.
</p>
<p>The three arguments (in order: <var>CARD</var>,<var>DEV</var>,<var>SUBDEV</var>)
specify card number or identifier, device number and subdevice number
(-1 means any).
</p>
<p>To see the list of cards currently recognized by your system check the
files ‘<tt>/proc/asound/cards</tt>’ and ‘<tt>/proc/asound/devices</tt>’.
</p>
<p>For example to capture with <code>avconv</code> from an ALSA device with
card id 0, you may run the command:
</p><table><tr><td> </td><td><pre class="example">avconv -f alsa -i hw:0 alsaout.wav
</pre></td></tr></table>
<p>For more information see:
<a href="http://www.alsa-project.org/alsa-doc/alsa-lib/pcm.html">http://www.alsa-project.org/alsa-doc/alsa-lib/pcm.html</a>
</p>
<a name="bktr"></a>
<h2 class="section"><a href="avconv.html#toc-bktr">16.2 bktr</a></h2>
<p>BSD video input device.
</p>
<a name="dv1394"></a>
<h2 class="section"><a href="avconv.html#toc-dv1394">16.3 dv1394</a></h2>
<p>Linux DV 1394 input device.
</p>
<a name="fbdev"></a>
<h2 class="section"><a href="avconv.html#toc-fbdev">16.4 fbdev</a></h2>
<p>Linux framebuffer input device.
</p>
<p>The Linux framebuffer is a graphic hardware-independent abstraction
layer to show graphics on a computer monitor, typically on the
console. It is accessed through a file device node, usually
‘<tt>/dev/fb0</tt>’.
</p>
<p>For more detailed information read the file
Documentation/fb/framebuffer.txt included in the Linux source tree.
</p>
<p>To record from the framebuffer device ‘<tt>/dev/fb0</tt>’ with
<code>avconv</code>:
</p><table><tr><td> </td><td><pre class="example">avconv -f fbdev -r 10 -i /dev/fb0 out.avi
</pre></td></tr></table>
<p>You can take a single screenshot image with the command:
</p><table><tr><td> </td><td><pre class="example">avconv -f fbdev -frames:v 1 -r 1 -i /dev/fb0 screenshot.jpeg
</pre></td></tr></table>
<p>See also <a href="http://linux-fbdev.sourceforge.net/">http://linux-fbdev.sourceforge.net/</a>, and fbset(1).
</p>
<a name="jack"></a>
<h2 class="section"><a href="avconv.html#toc-jack">16.5 jack</a></h2>
<p>JACK input device.
</p>
<p>To enable this input device during configuration you need libjack
installed on your system.
</p>
<p>A JACK input device creates one or more JACK writable clients, one for
each audio channel, with name <var>client_name</var>:input_<var>N</var>, where
<var>client_name</var> is the name provided by the application, and <var>N</var>
is a number which identifies the channel.
Each writable client will send the acquired data to the Libav input
device.
</p>
<p>Once you have created one or more JACK readable clients, you need to
connect them to one or more JACK writable clients.
</p>
<p>To connect or disconnect JACK clients you can use the
‘<tt>jack_connect</tt>’ and ‘<tt>jack_disconnect</tt>’ programs, or do it
through a graphical interface, for example with ‘<tt>qjackctl</tt>’.
</p>
<p>To list the JACK clients and their properties you can invoke the command
‘<tt>jack_lsp</tt>’.
</p>
<p>Follows an example which shows how to capture a JACK readable client
with <code>avconv</code>.
</p><table><tr><td> </td><td><pre class="example"># Create a JACK writable client with name "libav".
$ avconv -f jack -i libav -y out.wav
# Start the sample jack_metro readable client.
$ jack_metro -b 120 -d 0.2 -f 4000
# List the current JACK clients.
$ jack_lsp -c
system:capture_1
system:capture_2
system:playback_1
system:playback_2
libav:input_1
metro:120_bpm
# Connect metro to the avconv writable client.
$ jack_connect metro:120_bpm libav:input_1
</pre></td></tr></table>
<p>For more information read:
<a href="http://jackaudio.org/">http://jackaudio.org/</a>
</p>
<a name="libdc1394"></a>
<h2 class="section"><a href="avconv.html#toc-libdc1394">16.6 libdc1394</a></h2>
<p>IIDC1394 input device, based on libdc1394 and libraw1394.
</p>
<a name="oss-1"></a>
<h2 class="section"><a href="avconv.html#toc-oss-1">16.7 oss</a></h2>
<p>Open Sound System input device.
</p>
<p>The filename to provide to the input device is the device node
representing the OSS input device, and is usually set to
‘<tt>/dev/dsp</tt>’.
</p>
<p>For example to grab from ‘<tt>/dev/dsp</tt>’ using <code>avconv</code> use the
command:
</p><table><tr><td> </td><td><pre class="example">avconv -f oss -i /dev/dsp /tmp/oss.wav
</pre></td></tr></table>
<p>For more information about OSS see:
<a href="http://manuals.opensound.com/usersguide/dsp.html">http://manuals.opensound.com/usersguide/dsp.html</a>
</p>
<a name="pulse"></a>
<h2 class="section"><a href="avconv.html#toc-pulse">16.8 pulse</a></h2>
<p>pulseaudio input device.
</p>
<p>To enable this input device during configuration you need libpulse-simple
installed in your system.
</p>
<p>The filename to provide to the input device is a source device or the
string "default"
</p>
<p>To list the pulse source devices and their properties you can invoke
the command ‘<tt>pactl list sources</tt>’.
</p>
<table><tr><td> </td><td><pre class="example">avconv -f pulse -i default /tmp/pulse.wav
</pre></td></tr></table>
<a name="server-AVOption"></a>
<h3 class="subsection"><a href="avconv.html#toc-server-AVOption">16.8.1 <var>server</var> AVOption</a></h3>
<p>The syntax is:
</p><table><tr><td> </td><td><pre class="example">-server <var>server name</var>
</pre></td></tr></table>
<p>Connects to a specific server.
</p>
<a name="name-AVOption"></a>
<h3 class="subsection"><a href="avconv.html#toc-name-AVOption">16.8.2 <var>name</var> AVOption</a></h3>
<p>The syntax is:
</p><table><tr><td> </td><td><pre class="example">-name <var>application name</var>
</pre></td></tr></table>
<p>Specify the application name pulse will use when showing active clients,
by default it is "libav"
</p>
<a name="stream_005fname-AVOption"></a>
<h3 class="subsection"><a href="avconv.html#toc-stream_005fname-AVOption">16.8.3 <var>stream_name</var> AVOption</a></h3>
<p>The syntax is:
</p><table><tr><td> </td><td><pre class="example">-stream_name <var>stream name</var>
</pre></td></tr></table>
<p>Specify the stream name pulse will use when showing active streams,
by default it is "record"
</p>
<a name="sample_005frate-AVOption"></a>
<h3 class="subsection"><a href="avconv.html#toc-sample_005frate-AVOption">16.8.4 <var>sample_rate</var> AVOption</a></h3>
<p>The syntax is:
</p><table><tr><td> </td><td><pre class="example">-sample_rate <var>samplerate</var>
</pre></td></tr></table>
<p>Specify the samplerate in Hz, by default 48kHz is used.
</p>
<a name="channels-AVOption"></a>
<h3 class="subsection"><a href="avconv.html#toc-channels-AVOption">16.8.5 <var>channels</var> AVOption</a></h3>
<p>The syntax is:
</p><table><tr><td> </td><td><pre class="example">-channels <var>N</var>
</pre></td></tr></table>
<p>Specify the channels in use, by default 2 (stereo) is set.
</p>
<a name="frame_005fsize-AVOption"></a>
<h3 class="subsection"><a href="avconv.html#toc-frame_005fsize-AVOption">16.8.6 <var>frame_size</var> AVOption</a></h3>
<p>The syntax is:
</p><table><tr><td> </td><td><pre class="example">-frame_size <var>bytes</var>
</pre></td></tr></table>
<p>Specify the number of byte per frame, by default it is set to 1024.
</p>
<a name="fragment_005fsize-AVOption"></a>
<h3 class="subsection"><a href="avconv.html#toc-fragment_005fsize-AVOption">16.8.7 <var>fragment_size</var> AVOption</a></h3>
<p>The syntax is:
</p><table><tr><td> </td><td><pre class="example">-fragment_size <var>bytes</var>
</pre></td></tr></table>
<p>Specify the minimal buffering fragment in pulseaudio, it will affect the
audio latency. By default it is unset.
</p>
<a name="sndio-1"></a>
<h2 class="section"><a href="avconv.html#toc-sndio-1">16.9 sndio</a></h2>
<p>sndio input device.
</p>
<p>To enable this input device during configuration you need libsndio
installed on your system.
</p>
<p>The filename to provide to the input device is the device node
representing the sndio input device, and is usually set to
‘<tt>/dev/audio0</tt>’.
</p>
<p>For example to grab from ‘<tt>/dev/audio0</tt>’ using <code>avconv</code> use the
command:
</p><table><tr><td> </td><td><pre class="example">avconv -f sndio -i /dev/audio0 /tmp/oss.wav
</pre></td></tr></table>
<a name="video4linux2"></a>
<h2 class="section"><a href="avconv.html#toc-video4linux2">16.10 video4linux2</a></h2>
<p>Video4Linux2 input video device.
</p>
<p>The name of the device to grab is a file device node, usually Linux
systems tend to automatically create such nodes when the device
(e.g. an USB webcam) is plugged into the system, and has a name of the
kind ‘<tt>/dev/video<var>N</var></tt>’, where <var>N</var> is a number associated to
the device.
</p>
<p>Video4Linux2 devices usually support a limited set of
<var>width</var>x<var>height</var> sizes and framerates. You can check which are
supported using <code>-list_formats all</code> for Video4Linux2 devices.
</p>
<p>Some usage examples of the video4linux2 devices with avconv and avplay:
</p>
<table><tr><td> </td><td><pre class="example"># Grab and show the input of a video4linux2 device.
avplay -f video4linux2 -framerate 30 -video_size hd720 /dev/video0
# Grab and record the input of a video4linux2 device, leave the
framerate and size as previously set.
avconv -f video4linux2 -input_format mjpeg -i /dev/video0 out.mpeg
</pre></td></tr></table>
<a name="vfwcap"></a>
<h2 class="section"><a href="avconv.html#toc-vfwcap">16.11 vfwcap</a></h2>
<p>VfW (Video for Windows) capture input device.
</p>
<p>The filename passed as input is the capture driver number, ranging from
0 to 9. You may use "list" as filename to print a list of drivers. Any
other filename will be interpreted as device number 0.
</p>
<a name="x11grab"></a>
<h2 class="section"><a href="avconv.html#toc-x11grab">16.12 x11grab</a></h2>
<p>X11 video input device.
</p>
<p>This device allows to capture a region of an X11 display.
</p>
<p>The filename passed as input has the syntax:
</p><table><tr><td> </td><td><pre class="example">[<var>hostname</var>]:<var>display_number</var>.<var>screen_number</var>[+<var>x_offset</var>,<var>y_offset</var>]
</pre></td></tr></table>
<p><var>hostname</var>:<var>display_number</var>.<var>screen_number</var> specifies the
X11 display name of the screen to grab from. <var>hostname</var> can be
omitted, and defaults to "localhost". The environment variable
<code>DISPLAY</code> contains the default display name.
</p>
<p><var>x_offset</var> and <var>y_offset</var> specify the offsets of the grabbed
area with respect to the top-left border of the X11 screen. They
default to 0.
</p>
<p>Check the X11 documentation (e.g. man X) for more detailed information.
</p>
<p>Use the ‘<tt>dpyinfo</tt>’ program for getting basic information about the
properties of your X11 display (e.g. grep for "name" or "dimensions").
</p>
<p>For example to grab from ‘<tt>:0.0</tt>’ using <code>avconv</code>:
</p><table><tr><td> </td><td><pre class="example">avconv -f x11grab -r 25 -s cif -i :0.0 out.mpg
# Grab at position 10,20.
avconv -f x11grab -r 25 -s cif -i :0.0+10,20 out.mpg
</pre></td></tr></table>
<a name="follow_005fmouse-AVOption"></a>
<h3 class="subsection"><a href="avconv.html#toc-follow_005fmouse-AVOption">16.12.1 <var>follow_mouse</var> AVOption</a></h3>
<p>The syntax is:
</p><table><tr><td> </td><td><pre class="example">-follow_mouse centered|<var>PIXELS</var>
</pre></td></tr></table>
<p>When it is specified with "centered", the grabbing region follows the mouse
pointer and keeps the pointer at the center of region; otherwise, the region
follows only when the mouse pointer reaches within <var>PIXELS</var> (greater than
zero) to the edge of region.
</p>
<p>For example:
</p><table><tr><td> </td><td><pre class="example">avconv -f x11grab -follow_mouse centered -r 25 -s cif -i :0.0 out.mpg
# Follows only when the mouse pointer reaches within 100 pixels to edge
avconv -f x11grab -follow_mouse 100 -r 25 -s cif -i :0.0 out.mpg
</pre></td></tr></table>
<a name="show_005fregion-AVOption"></a>
<h3 class="subsection"><a href="avconv.html#toc-show_005fregion-AVOption">16.12.2 <var>show_region</var> AVOption</a></h3>
<p>The syntax is:
</p><table><tr><td> </td><td><pre class="example">-show_region 1
</pre></td></tr></table>
<p>If <var>show_region</var> AVOption is specified with <var>1</var>, then the grabbing
region will be indicated on screen. With this option, it’s easy to know what is
being grabbed if only a portion of the screen is grabbed.
</p>
<p>For example:
</p><table><tr><td> </td><td><pre class="example">avconv -f x11grab -show_region 1 -r 25 -s cif -i :0.0+10,20 out.mpg
# With follow_mouse
avconv -f x11grab -follow_mouse centered -show_region 1 -r 25 -s cif -i :0.0 out.mpg
</pre></td></tr></table>
<a name="Output-Devices"></a>
<h1 class="chapter"><a href="avconv.html#toc-Output-Devices">17. Output Devices</a></h1>
<p>Output devices are configured elements in Libav which allow to write
multimedia data to an output device attached to your system.
</p>
<p>When you configure your Libav build, all the supported output devices
are enabled by default. You can list all available ones using the
configure option "–list-outdevs".
</p>
<p>You can disable all the output devices using the configure option
"–disable-outdevs", and selectively enable an output device using the
option "–enable-outdev=<var>OUTDEV</var>", or you can disable a particular
input device using the option "–disable-outdev=<var>OUTDEV</var>".
</p>
<p>The option "-formats" of the av* tools will display the list of
enabled output devices (amongst the muxers).
</p>
<p>A description of the currently available output devices follows.
</p>
<a name="alsa"></a>
<h2 class="section"><a href="avconv.html#toc-alsa">17.1 alsa</a></h2>
<p>ALSA (Advanced Linux Sound Architecture) output device.
</p>
<a name="oss"></a>
<h2 class="section"><a href="avconv.html#toc-oss">17.2 oss</a></h2>
<p>OSS (Open Sound System) output device.
</p>
<a name="sndio"></a>
<h2 class="section"><a href="avconv.html#toc-sndio">17.3 sndio</a></h2>
<p>sndio audio output device.
</p>
<a name="Protocols"></a>
<h1 class="chapter"><a href="avconv.html#toc-Protocols">18. Protocols</a></h1>
<p>Protocols are configured elements in Libav which allow to access
resources which require the use of a particular protocol.
</p>
<p>When you configure your Libav build, all the supported protocols are
enabled by default. You can list all available ones using the
configure option "–list-protocols".
</p>
<p>You can disable all the protocols using the configure option
"–disable-protocols", and selectively enable a protocol using the
option "–enable-protocol=<var>PROTOCOL</var>", or you can disable a
particular protocol using the option
"–disable-protocol=<var>PROTOCOL</var>".
</p>
<p>The option "-protocols" of the av* tools will display the list of
supported protocols.
</p>
<p>A description of the currently available protocols follows.
</p>
<a name="concat"></a>
<h2 class="section"><a href="avconv.html#toc-concat">18.1 concat</a></h2>
<p>Physical concatenation protocol.
</p>
<p>Allow to read and seek from many resource in sequence as if they were
a unique resource.
</p>
<p>A URL accepted by this protocol has the syntax:
</p><table><tr><td> </td><td><pre class="example">concat:<var>URL1</var>|<var>URL2</var>|...|<var>URLN</var>
</pre></td></tr></table>
<p>where <var>URL1</var>, <var>URL2</var>, ..., <var>URLN</var> are the urls of the
resource to be concatenated, each one possibly specifying a distinct
protocol.
</p>
<p>For example to read a sequence of files ‘<tt>split1.mpeg</tt>’,
‘<tt>split2.mpeg</tt>’, ‘<tt>split3.mpeg</tt>’ with <code>avplay</code> use the
command:
</p><table><tr><td> </td><td><pre class="example">avplay concat:split1.mpeg\|split2.mpeg\|split3.mpeg
</pre></td></tr></table>
<p>Note that you may need to escape the character "|" which is special for
many shells.
</p>
<a name="file"></a>
<h2 class="section"><a href="avconv.html#toc-file">18.2 file</a></h2>
<p>File access protocol.
</p>
<p>Allow to read from or read to a file.
</p>
<p>For example to read from a file ‘<tt>input.mpeg</tt>’ with <code>avconv</code>
use the command:
</p><table><tr><td> </td><td><pre class="example">avconv -i file:input.mpeg output.mpeg
</pre></td></tr></table>
<p>The av* tools default to the file protocol, that is a resource
specified with the name "FILE.mpeg" is interpreted as the URL
"file:FILE.mpeg".
</p>
<a name="gopher"></a>
<h2 class="section"><a href="avconv.html#toc-gopher">18.3 gopher</a></h2>
<p>Gopher protocol.
</p>
<a name="hls-2"></a>
<h2 class="section"><a href="avconv.html#toc-hls-2">18.4 hls</a></h2>
<p>Read Apple HTTP Live Streaming compliant segmented stream as
a uniform one. The M3U8 playlists describing the segments can be
remote HTTP resources or local files, accessed using the standard
file protocol.
The nested protocol is declared by specifying
"+<var>proto</var>" after the hls URI scheme name, where <var>proto</var>
is either "file" or "http".
</p>
<table><tr><td> </td><td><pre class="example">hls+http://host/path/to/remote/resource.m3u8
hls+file://path/to/local/resource.m3u8
</pre></td></tr></table>
<p>Using this protocol is discouraged - the hls demuxer should work
just as well (if not, please report the issues) and is more complete.
To use the hls demuxer instead, simply use the direct URLs to the
m3u8 files.
</p>
<a name="http"></a>
<h2 class="section"><a href="avconv.html#toc-http">18.5 http</a></h2>
<p>HTTP (Hyper Text Transfer Protocol).
</p>
<p>This protocol accepts the following options:
</p>
<dl compact="compact">
<dt> ‘<samp>chunked_post</samp>’</dt>
<dd><p>If set to 1 use chunked Transfer-Encoding for posts, default is 1.
</p>
</dd>
<dt> ‘<samp>content_type</samp>’</dt>
<dd><p>Set a specific content type for the POST messages.
</p>
</dd>
<dt> ‘<samp>headers</samp>’</dt>
<dd><p>Set custom HTTP headers, can override built in default headers. The
value must be a string encoding the headers.
</p>
</dd>
<dt> ‘<samp>multiple_requests</samp>’</dt>
<dd><p>Use persistent connections if set to 1, default is 0.
</p>
</dd>
<dt> ‘<samp>post_data</samp>’</dt>
<dd><p>Set custom HTTP post data.
</p>
</dd>
<dt> ‘<samp>user_agent</samp>’</dt>
<dd><p>Override the User-Agent header. If not specified a string of the form
"Lavf/<version>" will be used.
</p>
</dd>
<dt> ‘<samp>mime_type</samp>’</dt>
<dd><p>Export the MIME type.
</p>
</dd>
<dt> ‘<samp>icy</samp>’</dt>
<dd><p>If set to 1 request ICY (SHOUTcast) metadata from the server. If the server
supports this, the metadata has to be retrieved by the application by reading
the ‘<samp>icy_metadata_headers</samp>’ and ‘<samp>icy_metadata_packet</samp>’ options.
The default is 1.
</p>
</dd>
<dt> ‘<samp>icy_metadata_headers</samp>’</dt>
<dd><p>If the server supports ICY metadata, this contains the ICY-specific HTTP reply
headers, separated by newline characters.
</p>
</dd>
<dt> ‘<samp>icy_metadata_packet</samp>’</dt>
<dd><p>If the server supports ICY metadata, and ‘<samp>icy</samp>’ was set to 1, this
contains the last non-empty metadata packet sent by the server. It should be
polled in regular intervals by applications interested in mid-stream metadata
updates.
</p>
</dd>
<dt> ‘<samp>offset</samp>’</dt>
<dd><p>Set initial byte offset.
</p>
</dd>
<dt> ‘<samp>end_offset</samp>’</dt>
<dd><p>Try to limit the request to bytes preceding this offset.
</p></dd>
</dl>
<a name="Icecast"></a>
<h2 class="section"><a href="avconv.html#toc-Icecast">18.6 Icecast</a></h2>
<p>Icecast (stream to Icecast servers)
</p>
<p>This protocol accepts the following options:
</p>
<dl compact="compact">
<dt> ‘<samp>ice_genre</samp>’</dt>
<dd><p>Set the stream genre.
</p>
</dd>
<dt> ‘<samp>ice_name</samp>’</dt>
<dd><p>Set the stream name.
</p>
</dd>
<dt> ‘<samp>ice_description</samp>’</dt>
<dd><p>Set the stream description.
</p>
</dd>
<dt> ‘<samp>ice_url</samp>’</dt>
<dd><p>Set the stream website URL.
</p>
</dd>
<dt> ‘<samp>ice_public</samp>’</dt>
<dd><p>Set if the stream should be public or not.
The default is 0 (not public).
</p>
</dd>
<dt> ‘<samp>user_agent</samp>’</dt>
<dd><p>Override the User-Agent header. If not specified a string of the form
"Lavf/<version>" will be used.
</p>
</dd>
<dt> ‘<samp>password</samp>’</dt>
<dd><p>Set the Icecast mountpoint password.
</p>
</dd>
<dt> ‘<samp>content_type</samp>’</dt>
<dd><p>Set the stream content type. This must be set if it is different from
audio/mpeg.
</p>
</dd>
<dt> ‘<samp>legacy_icecast</samp>’</dt>
<dd><p>This enables support for Icecast versions < 2.4.0, that do not support the
HTTP PUT method but the SOURCE method.
</p>
</dd>
</dl>
<a name="mmst"></a>
<h2 class="section"><a href="avconv.html#toc-mmst">18.7 mmst</a></h2>
<p>MMS (Microsoft Media Server) protocol over TCP.
</p>
<a name="mmsh"></a>
<h2 class="section"><a href="avconv.html#toc-mmsh">18.8 mmsh</a></h2>
<p>MMS (Microsoft Media Server) protocol over HTTP.
</p>
<p>The required syntax is:
</p><table><tr><td> </td><td><pre class="example">mmsh://<var>server</var>[:<var>port</var>][/<var>app</var>][/<var>playpath</var>]
</pre></td></tr></table>
<a name="md5"></a>
<h2 class="section"><a href="avconv.html#toc-md5">18.9 md5</a></h2>
<p>MD5 output protocol.
</p>
<p>Computes the MD5 hash of the data to be written, and on close writes
this to the designated output or stdout if none is specified. It can
be used to test muxers without writing an actual file.
</p>
<p>Some examples follow.
</p><table><tr><td> </td><td><pre class="example"># Write the MD5 hash of the encoded AVI file to the file output.avi.md5.
avconv -i input.flv -f avi -y md5:output.avi.md5
# Write the MD5 hash of the encoded AVI file to stdout.
avconv -i input.flv -f avi -y md5:
</pre></td></tr></table>
<p>Note that some formats (typically MOV) require the output protocol to
be seekable, so they will fail with the MD5 output protocol.
</p>
<a name="pipe"></a>
<h2 class="section"><a href="avconv.html#toc-pipe">18.10 pipe</a></h2>
<p>UNIX pipe access protocol.
</p>
<p>Allow to read and write from UNIX pipes.
</p>
<p>The accepted syntax is:
</p><table><tr><td> </td><td><pre class="example">pipe:[<var>number</var>]
</pre></td></tr></table>
<p><var>number</var> is the number corresponding to the file descriptor of the
pipe (e.g. 0 for stdin, 1 for stdout, 2 for stderr). If <var>number</var>
is not specified, by default the stdout file descriptor will be used
for writing, stdin for reading.
</p>
<p>For example to read from stdin with <code>avconv</code>:
</p><table><tr><td> </td><td><pre class="example">cat test.wav | avconv -i pipe:0
# ...this is the same as...
cat test.wav | avconv -i pipe:
</pre></td></tr></table>
<p>For writing to stdout with <code>avconv</code>:
</p><table><tr><td> </td><td><pre class="example">avconv -i test.wav -f avi pipe:1 | cat > test.avi
# ...this is the same as...
avconv -i test.wav -f avi pipe: | cat > test.avi
</pre></td></tr></table>
<p>Note that some formats (typically MOV), require the output protocol to
be seekable, so they will fail with the pipe output protocol.
</p>
<a name="rtmp"></a>
<h2 class="section"><a href="avconv.html#toc-rtmp">18.11 rtmp</a></h2>
<p>Real-Time Messaging Protocol.
</p>
<p>The Real-Time Messaging Protocol (RTMP) is used for streaming multimedia
content across a TCP/IP network.
</p>
<p>The required syntax is:
</p><table><tr><td> </td><td><pre class="example">rtmp://[<var>username</var>:<var>password</var>@]<var>server</var>[:<var>port</var>][/<var>app</var>][/<var>instance</var>][/<var>playpath</var>]
</pre></td></tr></table>
<p>The accepted parameters are:
</p><dl compact="compact">
<dt> ‘<samp>username</samp>’</dt>
<dd><p>An optional username (mostly for publishing).
</p>
</dd>
<dt> ‘<samp>password</samp>’</dt>
<dd><p>An optional password (mostly for publishing).
</p>
</dd>
<dt> ‘<samp>server</samp>’</dt>
<dd><p>The address of the RTMP server.
</p>
</dd>
<dt> ‘<samp>port</samp>’</dt>
<dd><p>The number of the TCP port to use (by default is 1935).
</p>
</dd>
<dt> ‘<samp>app</samp>’</dt>
<dd><p>It is the name of the application to access. It usually corresponds to
the path where the application is installed on the RTMP server
(e.g. ‘<tt>/ondemand/</tt>’, ‘<tt>/flash/live/</tt>’, etc.). You can override
the value parsed from the URI through the <code>rtmp_app</code> option, too.
</p>
</dd>
<dt> ‘<samp>playpath</samp>’</dt>
<dd><p>It is the path or name of the resource to play with reference to the
application specified in <var>app</var>, may be prefixed by "mp4:". You
can override the value parsed from the URI through the <code>rtmp_playpath</code>
option, too.
</p>
</dd>
<dt> ‘<samp>listen</samp>’</dt>
<dd><p>Act as a server, listening for an incoming connection.
</p>
</dd>
<dt> ‘<samp>timeout</samp>’</dt>
<dd><p>Maximum time to wait for the incoming connection. Implies listen.
</p></dd>
</dl>
<p>Additionally, the following parameters can be set via command line options
(or in code via <code>AVOption</code>s):
</p><dl compact="compact">
<dt> ‘<samp>rtmp_app</samp>’</dt>
<dd><p>Name of application to connect on the RTMP server. This option
overrides the parameter specified in the URI.
</p>
</dd>
<dt> ‘<samp>rtmp_buffer</samp>’</dt>
<dd><p>Set the client buffer time in milliseconds. The default is 3000.
</p>
</dd>
<dt> ‘<samp>rtmp_conn</samp>’</dt>
<dd><p>Extra arbitrary AMF connection parameters, parsed from a string,
e.g. like <code>B:1 S:authMe O:1 NN:code:1.23 NS:flag:ok O:0</code>.
Each value is prefixed by a single character denoting the type,
B for Boolean, N for number, S for string, O for object, or Z for null,
followed by a colon. For Booleans the data must be either 0 or 1 for
FALSE or TRUE, respectively. Likewise for Objects the data must be 0 or
1 to end or begin an object, respectively. Data items in subobjects may
be named, by prefixing the type with ’N’ and specifying the name before
the value (i.e. <code>NB:myFlag:1</code>). This option may be used multiple
times to construct arbitrary AMF sequences.
</p>
</dd>
<dt> ‘<samp>rtmp_flashver</samp>’</dt>
<dd><p>Version of the Flash plugin used to run the SWF player. The default
is LNX 9,0,124,2. (When publishing, the default is FMLE/3.0 (compatible;
<libavformat version>).)
</p>
</dd>
<dt> ‘<samp>rtmp_flush_interval</samp>’</dt>
<dd><p>Number of packets flushed in the same request (RTMPT only). The default
is 10.
</p>
</dd>
<dt> ‘<samp>rtmp_live</samp>’</dt>
<dd><p>Specify that the media is a live stream. No resuming or seeking in
live streams is possible. The default value is <code>any</code>, which means the
subscriber first tries to play the live stream specified in the
playpath. If a live stream of that name is not found, it plays the
recorded stream. The other possible values are <code>live</code> and
<code>recorded</code>.
</p>
</dd>
<dt> ‘<samp>rtmp_pageurl</samp>’</dt>
<dd><p>URL of the web page in which the media was embedded. By default no
value will be sent.
</p>
</dd>
<dt> ‘<samp>rtmp_playpath</samp>’</dt>
<dd><p>Stream identifier to play or to publish. This option overrides the
parameter specified in the URI.
</p>
</dd>
<dt> ‘<samp>rtmp_subscribe</samp>’</dt>
<dd><p>Name of live stream to subscribe to. By default no value will be sent.
It is only sent if the option is specified or if rtmp_live
is set to live.
</p>
</dd>
<dt> ‘<samp>rtmp_swfhash</samp>’</dt>
<dd><p>SHA256 hash of the decompressed SWF file (32 bytes).
</p>
</dd>
<dt> ‘<samp>rtmp_swfsize</samp>’</dt>
<dd><p>Size of the decompressed SWF file, required for SWFVerification.
</p>
</dd>
<dt> ‘<samp>rtmp_swfurl</samp>’</dt>
<dd><p>URL of the SWF player for the media. By default no value will be sent.
</p>
</dd>
<dt> ‘<samp>rtmp_swfverify</samp>’</dt>
<dd><p>URL to player swf file, compute hash/size automatically.
</p>
</dd>
<dt> ‘<samp>rtmp_tcurl</samp>’</dt>
<dd><p>URL of the target stream. Defaults to proto://host[:port]/app.
</p>
</dd>
</dl>
<p>For example to read with <code>avplay</code> a multimedia resource named
"sample" from the application "vod" from an RTMP server "myserver":
</p><table><tr><td> </td><td><pre class="example">avplay rtmp://myserver/vod/sample
</pre></td></tr></table>
<p>To publish to a password protected server, passing the playpath and
app names separately:
</p><table><tr><td> </td><td><pre class="example">avconv -re -i <input> -f flv -rtmp_playpath some/long/path -rtmp_app long/app/name rtmp://username:password@myserver/
</pre></td></tr></table>
<a name="rtmpe"></a>
<h2 class="section"><a href="avconv.html#toc-rtmpe">18.12 rtmpe</a></h2>
<p>Encrypted Real-Time Messaging Protocol.
</p>
<p>The Encrypted Real-Time Messaging Protocol (RTMPE) is used for
streaming multimedia content within standard cryptographic primitives,
consisting of Diffie-Hellman key exchange and HMACSHA256, generating
a pair of RC4 keys.
</p>
<a name="rtmps"></a>
<h2 class="section"><a href="avconv.html#toc-rtmps">18.13 rtmps</a></h2>
<p>Real-Time Messaging Protocol over a secure SSL connection.
</p>
<p>The Real-Time Messaging Protocol (RTMPS) is used for streaming
multimedia content across an encrypted connection.
</p>
<a name="rtmpt"></a>
<h2 class="section"><a href="avconv.html#toc-rtmpt">18.14 rtmpt</a></h2>
<p>Real-Time Messaging Protocol tunneled through HTTP.
</p>
<p>The Real-Time Messaging Protocol tunneled through HTTP (RTMPT) is used
for streaming multimedia content within HTTP requests to traverse
firewalls.
</p>
<a name="rtmpte"></a>
<h2 class="section"><a href="avconv.html#toc-rtmpte">18.15 rtmpte</a></h2>
<p>Encrypted Real-Time Messaging Protocol tunneled through HTTP.
</p>
<p>The Encrypted Real-Time Messaging Protocol tunneled through HTTP (RTMPTE)
is used for streaming multimedia content within HTTP requests to traverse
firewalls.
</p>
<a name="rtmpts"></a>
<h2 class="section"><a href="avconv.html#toc-rtmpts">18.16 rtmpts</a></h2>
<p>Real-Time Messaging Protocol tunneled through HTTPS.
</p>
<p>The Real-Time Messaging Protocol tunneled through HTTPS (RTMPTS) is used
for streaming multimedia content within HTTPS requests to traverse
firewalls.
</p>
<a name="librtmp-rtmp_002c-rtmpe_002c-rtmps_002c-rtmpt_002c-rtmpte"></a>
<h2 class="section"><a href="avconv.html#toc-librtmp-rtmp_002c-rtmpe_002c-rtmps_002c-rtmpt_002c-rtmpte">18.17 librtmp rtmp, rtmpe, rtmps, rtmpt, rtmpte</a></h2>
<p>Real-Time Messaging Protocol and its variants supported through
librtmp.
</p>
<p>Requires the presence of the librtmp headers and library during
configuration. You need to explicitly configure the build with
"–enable-librtmp". If enabled this will replace the native RTMP
protocol.
</p>
<p>This protocol provides most client functions and a few server
functions needed to support RTMP, RTMP tunneled in HTTP (RTMPT),
encrypted RTMP (RTMPE), RTMP over SSL/TLS (RTMPS) and tunneled
variants of these encrypted types (RTMPTE, RTMPTS).
</p>
<p>The required syntax is:
</p><table><tr><td> </td><td><pre class="example"><var>rtmp_proto</var>://<var>server</var>[:<var>port</var>][/<var>app</var>][/<var>playpath</var>] <var>options</var>
</pre></td></tr></table>
<p>where <var>rtmp_proto</var> is one of the strings "rtmp", "rtmpt", "rtmpe",
"rtmps", "rtmpte", "rtmpts" corresponding to each RTMP variant, and
<var>server</var>, <var>port</var>, <var>app</var> and <var>playpath</var> have the same
meaning as specified for the RTMP native protocol.
<var>options</var> contains a list of space-separated options of the form
<var>key</var>=<var>val</var>.
</p>
<p>See the librtmp manual page (man 3 librtmp) for more information.
</p>
<p>For example, to stream a file in real-time to an RTMP server using
<code>avconv</code>:
</p><table><tr><td> </td><td><pre class="example">avconv -re -i myfile -f flv rtmp://myserver/live/mystream
</pre></td></tr></table>
<p>To play the same stream using <code>avplay</code>:
</p><table><tr><td> </td><td><pre class="example">avplay "rtmp://myserver/live/mystream live=1"
</pre></td></tr></table>
<a name="rtp"></a>
<h2 class="section"><a href="avconv.html#toc-rtp">18.18 rtp</a></h2>
<p>Real-Time Protocol.
</p>
<a name="rtsp"></a>
<h2 class="section"><a href="avconv.html#toc-rtsp">18.19 rtsp</a></h2>
<p>RTSP is not technically a protocol handler in libavformat, it is a demuxer
and muxer. The demuxer supports both normal RTSP (with data transferred
over RTP; this is used by e.g. Apple and Microsoft) and Real-RTSP (with
data transferred over RDT).
</p>
<p>The muxer can be used to send a stream using RTSP ANNOUNCE to a server
supporting it (currently Darwin Streaming Server and Mischa Spiegelmock’s
<a href="http://github.com/revmischa/rtsp-server">RTSP server</a>).
</p>
<p>The required syntax for a RTSP url is:
</p><table><tr><td> </td><td><pre class="example">rtsp://<var>hostname</var>[:<var>port</var>]/<var>path</var>
</pre></td></tr></table>
<p>The following options (set on the <code>avconv</code>/<code>avplay</code> command
line, or set in code via <code>AVOption</code>s or in <code>avformat_open_input</code>),
are supported:
</p>
<p>Flags for <code>rtsp_transport</code>:
</p>
<dl compact="compact">
<dt> ‘<samp>udp</samp>’</dt>
<dd><p>Use UDP as lower transport protocol.
</p>
</dd>
<dt> ‘<samp>tcp</samp>’</dt>
<dd><p>Use TCP (interleaving within the RTSP control channel) as lower
transport protocol.
</p>
</dd>
<dt> ‘<samp>udp_multicast</samp>’</dt>
<dd><p>Use UDP multicast as lower transport protocol.
</p>
</dd>
<dt> ‘<samp>http</samp>’</dt>
<dd><p>Use HTTP tunneling as lower transport protocol, which is useful for
passing proxies.
</p></dd>
</dl>
<p>Multiple lower transport protocols may be specified, in that case they are
tried one at a time (if the setup of one fails, the next one is tried).
For the muxer, only the <code>tcp</code> and <code>udp</code> options are supported.
</p>
<p>Flags for <code>rtsp_flags</code>:
</p>
<dl compact="compact">
<dt> ‘<samp>filter_src</samp>’</dt>
<dd><p>Accept packets only from negotiated peer address and port.
</p></dd>
<dt> ‘<samp>listen</samp>’</dt>
<dd><p>Act as a server, listening for an incoming connection.
</p></dd>
</dl>
<p>When receiving data over UDP, the demuxer tries to reorder received packets
(since they may arrive out of order, or packets may get lost totally). This
can be disabled by setting the maximum demuxing delay to zero (via
the <code>max_delay</code> field of AVFormatContext).
</p>
<p>When watching multi-bitrate Real-RTSP streams with <code>avplay</code>, the
streams to display can be chosen with <code>-vst</code> <var>n</var> and
<code>-ast</code> <var>n</var> for video and audio respectively, and can be switched
on the fly by pressing <code>v</code> and <code>a</code>.
</p>
<p>Example command lines:
</p>
<p>To watch a stream over UDP, with a max reordering delay of 0.5 seconds:
</p>
<table><tr><td> </td><td><pre class="example">avplay -max_delay 500000 -rtsp_transport udp rtsp://server/video.mp4
</pre></td></tr></table>
<p>To watch a stream tunneled over HTTP:
</p>
<table><tr><td> </td><td><pre class="example">avplay -rtsp_transport http rtsp://server/video.mp4
</pre></td></tr></table>
<p>To send a stream in realtime to a RTSP server, for others to watch:
</p>
<table><tr><td> </td><td><pre class="example">avconv -re -i <var>input</var> -f rtsp -muxdelay 0.1 rtsp://server/live.sdp
</pre></td></tr></table>
<p>To receive a stream in realtime:
</p>
<table><tr><td> </td><td><pre class="example">avconv -rtsp_flags listen -i rtsp://ownaddress/live.sdp <var>output</var>
</pre></td></tr></table>
<a name="sap"></a>
<h2 class="section"><a href="avconv.html#toc-sap">18.20 sap</a></h2>
<p>Session Announcement Protocol (RFC 2974). This is not technically a
protocol handler in libavformat, it is a muxer and demuxer.
It is used for signalling of RTP streams, by announcing the SDP for the
streams regularly on a separate port.
</p>
<a name="Muxer"></a>
<h3 class="subsection"><a href="avconv.html#toc-Muxer">18.20.1 Muxer</a></h3>
<p>The syntax for a SAP url given to the muxer is:
</p><table><tr><td> </td><td><pre class="example">sap://<var>destination</var>[:<var>port</var>][?<var>options</var>]
</pre></td></tr></table>
<p>The RTP packets are sent to <var>destination</var> on port <var>port</var>,
or to port 5004 if no port is specified.
<var>options</var> is a <code>&</code>-separated list. The following options
are supported:
</p>
<dl compact="compact">
<dt> ‘<samp>announce_addr=<var>address</var></samp>’</dt>
<dd><p>Specify the destination IP address for sending the announcements to.
If omitted, the announcements are sent to the commonly used SAP
announcement multicast address 224.2.127.254 (sap.mcast.net), or
ff0e::2:7ffe if <var>destination</var> is an IPv6 address.
</p>
</dd>
<dt> ‘<samp>announce_port=<var>port</var></samp>’</dt>
<dd><p>Specify the port to send the announcements on, defaults to
9875 if not specified.
</p>
</dd>
<dt> ‘<samp>ttl=<var>ttl</var></samp>’</dt>
<dd><p>Specify the time to live value for the announcements and RTP packets,
defaults to 255.
</p>
</dd>
<dt> ‘<samp>same_port=<var>0|1</var></samp>’</dt>
<dd><p>If set to 1, send all RTP streams on the same port pair. If zero (the
default), all streams are sent on unique ports, with each stream on a
port 2 numbers higher than the previous.
VLC/Live555 requires this to be set to 1, to be able to receive the stream.
The RTP stack in libavformat for receiving requires all streams to be sent
on unique ports.
</p></dd>
</dl>
<p>Example command lines follow.
</p>
<p>To broadcast a stream on the local subnet, for watching in VLC:
</p>
<table><tr><td> </td><td><pre class="example">avconv -re -i <var>input</var> -f sap sap://224.0.0.255?same_port=1
</pre></td></tr></table>
<p>Similarly, for watching in avplay:
</p>
<table><tr><td> </td><td><pre class="example">avconv -re -i <var>input</var> -f sap sap://224.0.0.255
</pre></td></tr></table>
<p>And for watching in avplay, over IPv6:
</p>
<table><tr><td> </td><td><pre class="example">avconv -re -i <var>input</var> -f sap sap://[ff0e::1:2:3:4]
</pre></td></tr></table>
<a name="Demuxer"></a>
<h3 class="subsection"><a href="avconv.html#toc-Demuxer">18.20.2 Demuxer</a></h3>
<p>The syntax for a SAP url given to the demuxer is:
</p><table><tr><td> </td><td><pre class="example">sap://[<var>address</var>][:<var>port</var>]
</pre></td></tr></table>
<p><var>address</var> is the multicast address to listen for announcements on,
if omitted, the default 224.2.127.254 (sap.mcast.net) is used. <var>port</var>
is the port that is listened on, 9875 if omitted.
</p>
<p>The demuxers listens for announcements on the given address and port.
Once an announcement is received, it tries to receive that particular stream.
</p>
<p>Example command lines follow.
</p>
<p>To play back the first stream announced on the normal SAP multicast address:
</p>
<table><tr><td> </td><td><pre class="example">avplay sap://
</pre></td></tr></table>
<p>To play back the first stream announced on one the default IPv6 SAP multicast address:
</p>
<table><tr><td> </td><td><pre class="example">avplay sap://[ff0e::2:7ffe]
</pre></td></tr></table>
<a name="tcp"></a>
<h2 class="section"><a href="avconv.html#toc-tcp">18.21 tcp</a></h2>
<p>Trasmission Control Protocol.
</p>
<p>The required syntax for a TCP url is:
</p><table><tr><td> </td><td><pre class="example">tcp://<var>hostname</var>:<var>port</var>[?<var>options</var>]
</pre></td></tr></table>
<dl compact="compact">
<dt> ‘<samp>listen</samp>’</dt>
<dd><p>Listen for an incoming connection
</p>
<table><tr><td> </td><td><pre class="example">avconv -i <var>input</var> -f <var>format</var> tcp://<var>hostname</var>:<var>port</var>?listen
avplay tcp://<var>hostname</var>:<var>port</var>
</pre></td></tr></table>
</dd>
</dl>
<a name="tls"></a>
<h2 class="section"><a href="avconv.html#toc-tls">18.22 tls</a></h2>
<p>Transport Layer Security (TLS) / Secure Sockets Layer (SSL)
</p>
<p>The required syntax for a TLS url is:
</p><table><tr><td> </td><td><pre class="example">tls://<var>hostname</var>:<var>port</var>
</pre></td></tr></table>
<p>The following parameters can be set via command line options
(or in code via <code>AVOption</code>s):
</p>
<dl compact="compact">
<dt> ‘<samp>ca_file</samp>’</dt>
<dd><p>A file containing certificate authority (CA) root certificates to treat
as trusted. If the linked TLS library contains a default this might not
need to be specified for verification to work, but not all libraries and
setups have defaults built in.
</p>
</dd>
<dt> ‘<samp>tls_verify=<var>1|0</var></samp>’</dt>
<dd><p>If enabled, try to verify the peer that we are communicating with.
Note, if using OpenSSL, this currently only makes sure that the
peer certificate is signed by one of the root certificates in the CA
database, but it does not validate that the certificate actually
matches the host name we are trying to connect to. (With GnuTLS,
the host name is validated as well.)
</p>
<p>This is disabled by default since it requires a CA database to be
provided by the caller in many cases.
</p>
</dd>
<dt> ‘<samp>cert_file</samp>’</dt>
<dd><p>A file containing a certificate to use in the handshake with the peer.
(When operating as server, in listen mode, this is more often required
by the peer, while client certificates only are mandated in certain
setups.)
</p>
</dd>
<dt> ‘<samp>key_file</samp>’</dt>
<dd><p>A file containing the private key for the certificate.
</p>
</dd>
<dt> ‘<samp>listen=<var>1|0</var></samp>’</dt>
<dd><p>If enabled, listen for connections on the provided port, and assume
the server role in the handshake instead of the client role.
</p>
</dd>
</dl>
<a name="udp"></a>
<h2 class="section"><a href="avconv.html#toc-udp">18.23 udp</a></h2>
<p>User Datagram Protocol.
</p>
<p>The required syntax for a UDP url is:
</p><table><tr><td> </td><td><pre class="example">udp://<var>hostname</var>:<var>port</var>[?<var>options</var>]
</pre></td></tr></table>
<p><var>options</var> contains a list of &-separated options of the form <var>key</var>=<var>val</var>.
Follow the list of supported options.
</p>
<dl compact="compact">
<dt> ‘<samp>buffer_size=<var>size</var></samp>’</dt>
<dd><p>set the UDP buffer size in bytes
</p>
</dd>
<dt> ‘<samp>localport=<var>port</var></samp>’</dt>
<dd><p>override the local UDP port to bind with
</p>
</dd>
<dt> ‘<samp>localaddr=<var>addr</var></samp>’</dt>
<dd><p>Choose the local IP address. This is useful e.g. if sending multicast
and the host has multiple interfaces, where the user can choose
which interface to send on by specifying the IP address of that interface.
</p>
</dd>
<dt> ‘<samp>pkt_size=<var>size</var></samp>’</dt>
<dd><p>set the size in bytes of UDP packets
</p>
</dd>
<dt> ‘<samp>reuse=<var>1|0</var></samp>’</dt>
<dd><p>explicitly allow or disallow reusing UDP sockets
</p>
</dd>
<dt> ‘<samp>ttl=<var>ttl</var></samp>’</dt>
<dd><p>set the time to live value (for multicast only)
</p>
</dd>
<dt> ‘<samp>connect=<var>1|0</var></samp>’</dt>
<dd><p>Initialize the UDP socket with <code>connect()</code>. In this case, the
destination address can’t be changed with ff_udp_set_remote_url later.
If the destination address isn’t known at the start, this option can
be specified in ff_udp_set_remote_url, too.
This allows finding out the source address for the packets with getsockname,
and makes writes return with AVERROR(ECONNREFUSED) if "destination
unreachable" is received.
For receiving, this gives the benefit of only receiving packets from
the specified peer address/port.
</p>
</dd>
<dt> ‘<samp>sources=<var>address</var>[,<var>address</var>]</samp>’</dt>
<dd><p>Only receive packets sent to the multicast group from one of the
specified sender IP addresses.
</p>
</dd>
<dt> ‘<samp>block=<var>address</var>[,<var>address</var>]</samp>’</dt>
<dd><p>Ignore packets sent to the multicast group from the specified
sender IP addresses.
</p></dd>
</dl>
<p>Some usage examples of the udp protocol with <code>avconv</code> follow.
</p>
<p>To stream over UDP to a remote endpoint:
</p><table><tr><td> </td><td><pre class="example">avconv -i <var>input</var> -f <var>format</var> udp://<var>hostname</var>:<var>port</var>
</pre></td></tr></table>
<p>To stream in mpegts format over UDP using 188 sized UDP packets, using a large input buffer:
</p><table><tr><td> </td><td><pre class="example">avconv -i <var>input</var> -f mpegts udp://<var>hostname</var>:<var>port</var>?pkt_size=188&buffer_size=65535
</pre></td></tr></table>
<p>To receive over UDP from a remote endpoint:
</p><table><tr><td> </td><td><pre class="example">avconv -i udp://[<var>multicast-address</var>]:<var>port</var>
</pre></td></tr></table>
<a name="unix"></a>
<h2 class="section"><a href="avconv.html#toc-unix">18.24 unix</a></h2>
<p>Unix local socket
</p>
<p>The required syntax for a Unix socket URL is:
</p>
<table><tr><td> </td><td><pre class="example">unix://<var>filepath</var>
</pre></td></tr></table>
<p>The following parameters can be set via command line options
(or in code via <code>AVOption</code>s):
</p>
<dl compact="compact">
<dt> ‘<samp>timeout</samp>’</dt>
<dd><p>Timeout in ms.
</p></dd>
<dt> ‘<samp>listen</samp>’</dt>
<dd><p>Create the Unix socket in listening mode.
</p></dd>
</dl>
<a name="Bitstream-Filters"></a>
<h1 class="chapter"><a href="avconv.html#toc-Bitstream-Filters">19. Bitstream Filters</a></h1>
<p>When you configure your Libav build, all the supported bitstream
filters are enabled by default. You can list all available ones using
the configure option <code>--list-bsfs</code>.
</p>
<p>You can disable all the bitstream filters using the configure option
<code>--disable-bsfs</code>, and selectively enable any bitstream filter using
the option <code>--enable-bsf=BSF</code>, or you can disable a particular
bitstream filter using the option <code>--disable-bsf=BSF</code>.
</p>
<p>The option <code>-bsfs</code> of the av* tools will display the list of
all the supported bitstream filters included in your build.
</p>
<p>Below is a description of the currently available bitstream filters.
</p>
<a name="aac_005fadtstoasc"></a>
<h2 class="section"><a href="avconv.html#toc-aac_005fadtstoasc">19.1 aac_adtstoasc</a></h2>
<a name="chomp"></a>
<h2 class="section"><a href="avconv.html#toc-chomp">19.2 chomp</a></h2>
<a name="dump_005fextradata"></a>
<h2 class="section"><a href="avconv.html#toc-dump_005fextradata">19.3 dump_extradata</a></h2>
<a name="h264_005fmp4toannexb"></a>
<h2 class="section"><a href="avconv.html#toc-h264_005fmp4toannexb">19.4 h264_mp4toannexb</a></h2>
<a name="imx_005fdump_005fheader"></a>
<h2 class="section"><a href="avconv.html#toc-imx_005fdump_005fheader">19.5 imx_dump_header</a></h2>
<a name="mjpeg2jpeg"></a>
<h2 class="section"><a href="avconv.html#toc-mjpeg2jpeg">19.6 mjpeg2jpeg</a></h2>
<p>Convert MJPEG/AVI1 packets to full JPEG/JFIF packets.
</p>
<p>MJPEG is a video codec wherein each video frame is essentially a
JPEG image. The individual frames can be extracted without loss,
e.g. by
</p>
<table><tr><td> </td><td><pre class="example">avconv -i ../some_mjpeg.avi -c:v copy frames_%d.jpg
</pre></td></tr></table>
<p>Unfortunately, these chunks are incomplete JPEG images, because
they lack the DHT segment required for decoding. Quoting from
<a href="http://www.digitalpreservation.gov/formats/fdd/fdd000063.shtml">http://www.digitalpreservation.gov/formats/fdd/fdd000063.shtml</a>:
</p>
<p>Avery Lee, writing in the rec.video.desktop newsgroup in 2001,
commented that "MJPEG, or at least the MJPEG in AVIs having the
MJPG fourcc, is restricted JPEG with a fixed – and *omitted* –
Huffman table. The JPEG must be YCbCr colorspace, it must be 4:2:2,
and it must use basic Huffman encoding, not arithmetic or
progressive. . . . You can indeed extract the MJPEG frames and
decode them with a regular JPEG decoder, but you have to prepend
the DHT segment to them, or else the decoder won’t have any idea
how to decompress the data. The exact table necessary is given in
the OpenDML spec."
</p>
<p>This bitstream filter patches the header of frames extracted from an MJPEG
stream (carrying the AVI1 header ID and lacking a DHT segment) to
produce fully qualified JPEG images.
</p>
<table><tr><td> </td><td><pre class="example">avconv -i mjpeg-movie.avi -c:v copy -bsf:v mjpeg2jpeg frame_%d.jpg
exiftran -i -9 frame*.jpg
avconv -i frame_%d.jpg -c:v copy rotated.avi
</pre></td></tr></table>
<a name="mjpega_005fdump_005fheader"></a>
<h2 class="section"><a href="avconv.html#toc-mjpega_005fdump_005fheader">19.7 mjpega_dump_header</a></h2>
<a name="movsub"></a>
<h2 class="section"><a href="avconv.html#toc-movsub">19.8 movsub</a></h2>
<a name="mp3_005fheader_005fcompress"></a>
<h2 class="section"><a href="avconv.html#toc-mp3_005fheader_005fcompress">19.9 mp3_header_compress</a></h2>
<a name="mp3_005fheader_005fdecompress"></a>
<h2 class="section"><a href="avconv.html#toc-mp3_005fheader_005fdecompress">19.10 mp3_header_decompress</a></h2>
<a name="noise"></a>
<h2 class="section"><a href="avconv.html#toc-noise">19.11 noise</a></h2>
<a name="remove_005fextradata"></a>
<h2 class="section"><a href="avconv.html#toc-remove_005fextradata">19.12 remove_extradata</a></h2>
<a name="Filtergraph-description"></a>
<h1 class="chapter"><a href="avconv.html#toc-Filtergraph-description">20. Filtergraph description</a></h1>
<p>A filtergraph is a directed graph of connected filters. It can contain
cycles, and there can be multiple links between a pair of
filters. Each link has one input pad on one side connecting it to one
filter from which it takes its input, and one output pad on the other
side connecting it to one filter accepting its output.
</p>
<p>Each filter in a filtergraph is an instance of a filter class
registered in the application, which defines the features and the
number of input and output pads of the filter.
</p>
<p>A filter with no input pads is called a "source", and a filter with no
output pads is called a "sink".
</p>
<p><a name="Filtergraph-syntax"></a>
</p><a name="Filtergraph-syntax-1"></a>
<h2 class="section"><a href="avconv.html#toc-Filtergraph-syntax-1">20.1 Filtergraph syntax</a></h2>
<p>A filtergraph has a textual representation, which is
recognized by the ‘<samp>-filter</samp>’/‘<samp>-vf</samp>’ and ‘<samp>-filter_complex</samp>’
options in <code>avconv</code> and ‘<samp>-vf</samp>’ in <code>avplay</code>, and by the
<code>avfilter_graph_parse()</code>/<code>avfilter_graph_parse2()</code> functions defined in
‘<tt>libavfilter/avfilter.h</tt>’.
</p>
<p>A filterchain consists of a sequence of connected filters, each one
connected to the previous one in the sequence. A filterchain is
represented by a list of ","-separated filter descriptions.
</p>
<p>A filtergraph consists of a sequence of filterchains. A sequence of
filterchains is represented by a list of ";"-separated filterchain
descriptions.
</p>
<p>A filter is represented by a string of the form:
[<var>in_link_1</var>]...[<var>in_link_N</var>]<var>filter_name</var>=<var>arguments</var>[<var>out_link_1</var>]...[<var>out_link_M</var>]
</p>
<p><var>filter_name</var> is the name of the filter class of which the
described filter is an instance of, and has to be the name of one of
the filter classes registered in the program.
The name of the filter class is optionally followed by a string
"=<var>arguments</var>".
</p>
<p><var>arguments</var> is a string which contains the parameters used to
initialize the filter instance. It may have one of two forms:
</p><ul>
<li>
A ’:’-separated list of <var>key=value</var> pairs.
</li><li>
A ’:’-separated list of <var>value</var>. In this case, the keys are assumed to be
the option names in the order they are declared. E.g. the <code>fade</code> filter
declares three options in this order – ‘<samp>type</samp>’, ‘<samp>start_frame</samp>’ and
‘<samp>nb_frames</samp>’. Then the parameter list <var>in:0:30</var> means that the value
<var>in</var> is assigned to the option ‘<samp>type</samp>’, <var>0</var> to
‘<samp>start_frame</samp>’ and <var>30</var> to ‘<samp>nb_frames</samp>’.
</li></ul>
<p>If the option value itself is a list of items (e.g. the <code>format</code> filter
takes a list of pixel formats), the items in the list are usually separated by
’|’.
</p>
<p>The list of arguments can be quoted using the character "’" as initial
and ending mark, and the character ’\’ for escaping the characters
within the quoted text; otherwise the argument string is considered
terminated when the next special character (belonging to the set
"[]=;,") is encountered.
</p>
<p>The name and arguments of the filter are optionally preceded and
followed by a list of link labels.
A link label allows to name a link and associate it to a filter output
or input pad. The preceding labels <var>in_link_1</var>
... <var>in_link_N</var>, are associated to the filter input pads,
the following labels <var>out_link_1</var> ... <var>out_link_M</var>, are
associated to the output pads.
</p>
<p>When two link labels with the same name are found in the
filtergraph, a link between the corresponding input and output pad is
created.
</p>
<p>If an output pad is not labelled, it is linked by default to the first
unlabelled input pad of the next filter in the filterchain.
For example in the filterchain
</p><table><tr><td> </td><td><pre class="example">nullsrc, split[L1], [L2]overlay, nullsink
</pre></td></tr></table>
<p>the split filter instance has two output pads, and the overlay filter
instance two input pads. The first output pad of split is labelled
"L1", the first input pad of overlay is labelled "L2", and the second
output pad of split is linked to the second input pad of overlay,
which are both unlabelled.
</p>
<p>In a complete filterchain all the unlabelled filter input and output
pads must be connected. A filtergraph is considered valid if all the
filter input and output pads of all the filterchains are connected.
</p>
<p>Libavfilter will automatically insert <a href="#scale">scale</a> filters where format
conversion is required. It is possible to specify swscale flags
for those automatically inserted scalers by prepending
<code>sws_flags=<var>flags</var>;</code>
to the filtergraph description.
</p>
<p>Here is a BNF description of the filtergraph syntax:
</p><table><tr><td> </td><td><pre class="example"><var>NAME</var> ::= sequence of alphanumeric characters and '_'
<var>LINKLABEL</var> ::= "[" <var>NAME</var> "]"
<var>LINKLABELS</var> ::= <var>LINKLABEL</var> [<var>LINKLABELS</var>]
<var>FILTER_ARGUMENTS</var> ::= sequence of chars (possibly quoted)
<var>FILTER</var> ::= [<var>LINKLABELS</var>] <var>NAME</var> ["=" <var>FILTER_ARGUMENTS</var>] [<var>LINKLABELS</var>]
<var>FILTERCHAIN</var> ::= <var>FILTER</var> [,<var>FILTERCHAIN</var>]
<var>FILTERGRAPH</var> ::= [sws_flags=<var>flags</var>;] <var>FILTERCHAIN</var> [;<var>FILTERGRAPH</var>]
</pre></td></tr></table>
<a name="Audio-Filters"></a>
<h1 class="chapter"><a href="avconv.html#toc-Audio-Filters">21. Audio Filters</a></h1>
<p>When you configure your Libav build, you can disable any of the
existing filters using –disable-filters.
The configure output will show the audio filters included in your
build.
</p>
<p>Below is a description of the currently available audio filters.
</p>
<a name="aformat"></a>
<h2 class="section"><a href="avconv.html#toc-aformat">21.1 aformat</a></h2>
<p>Convert the input audio to one of the specified formats. The framework will
negotiate the most appropriate format to minimize conversions.
</p>
<p>It accepts the following parameters:
</p><dl compact="compact">
<dt> ‘<samp>sample_fmts</samp>’</dt>
<dd><p>A ’|’-separated list of requested sample formats.
</p>
</dd>
<dt> ‘<samp>sample_rates</samp>’</dt>
<dd><p>A ’|’-separated list of requested sample rates.
</p>
</dd>
<dt> ‘<samp>channel_layouts</samp>’</dt>
<dd><p>A ’|’-separated list of requested channel layouts.
</p>
</dd>
</dl>
<p>If a parameter is omitted, all values are allowed.
</p>
<p>Force the output to either unsigned 8-bit or signed 16-bit stereo
</p><table><tr><td> </td><td><pre class="example">aformat=sample_fmts=u8|s16:channel_layouts=stereo
</pre></td></tr></table>
<a name="amix"></a>
<h2 class="section"><a href="avconv.html#toc-amix">21.2 amix</a></h2>
<p>Mixes multiple audio inputs into a single output.
</p>
<p>For example
</p><table><tr><td> </td><td><pre class="example">avconv -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex amix=inputs=3:duration=first:dropout_transition=3 OUTPUT
</pre></td></tr></table>
<p>will mix 3 input audio streams to a single output with the same duration as the
first input and a dropout transition time of 3 seconds.
</p>
<p>It accepts the following parameters:
</p><dl compact="compact">
<dt> ‘<samp>inputs</samp>’</dt>
<dd><p>The number of inputs. If unspecified, it defaults to 2.
</p>
</dd>
<dt> ‘<samp>duration</samp>’</dt>
<dd><p>How to determine the end-of-stream.
</p><dl compact="compact">
<dt> ‘<samp>longest</samp>’</dt>
<dd><p>The duration of the longest input. (default)
</p>
</dd>
<dt> ‘<samp>shortest</samp>’</dt>
<dd><p>The duration of the shortest input.
</p>
</dd>
<dt> ‘<samp>first</samp>’</dt>
<dd><p>The duration of the first input.
</p>
</dd>
</dl>
</dd>
<dt> ‘<samp>dropout_transition</samp>’</dt>
<dd><p>The transition time, in seconds, for volume renormalization when an input
stream ends. The default value is 2 seconds.
</p>
</dd>
</dl>
<a name="anull"></a>
<h2 class="section"><a href="avconv.html#toc-anull">21.3 anull</a></h2>
<p>Pass the audio source unchanged to the output.
</p>
<a name="asetpts"></a>
<h2 class="section"><a href="avconv.html#toc-asetpts">21.4 asetpts</a></h2>
<p>Change the PTS (presentation timestamp) of the input audio frames.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>expr</samp>’</dt>
<dd><p>The expression which is evaluated for each frame to construct its timestamp.
</p>
</dd>
</dl>
<p>The expression is evaluated through the eval API and can contain the following
constants:
</p>
<dl compact="compact">
<dt> ‘<samp>PTS</samp>’</dt>
<dd><p>the presentation timestamp in input
</p>
</dd>
<dt> ‘<samp>E, PI, PHI</samp>’</dt>
<dd><p>These are approximated values for the mathematical constants e
(Euler’s number), pi (Greek pi), and phi (the golden ratio).
</p>
</dd>
<dt> ‘<samp>N</samp>’</dt>
<dd><p>The number of audio samples passed through the filter so far, starting at 0.
</p>
</dd>
<dt> ‘<samp>S</samp>’</dt>
<dd><p>The number of audio samples in the current frame.
</p>
</dd>
<dt> ‘<samp>SR</samp>’</dt>
<dd><p>The audio sample rate.
</p>
</dd>
<dt> ‘<samp>STARTPTS</samp>’</dt>
<dd><p>The PTS of the first frame.
</p>
</dd>
<dt> ‘<samp>PREV_INPTS</samp>’</dt>
<dd><p>The previous input PTS.
</p>
</dd>
<dt> ‘<samp>PREV_OUTPTS</samp>’</dt>
<dd><p>The previous output PTS.
</p>
</dd>
<dt> ‘<samp>RTCTIME</samp>’</dt>
<dd><p>The wallclock (RTC) time in microseconds.
</p>
</dd>
<dt> ‘<samp>RTCSTART</samp>’</dt>
<dd><p>The wallclock (RTC) time at the start of the movie in microseconds.
</p>
</dd>
</dl>
<p>Some examples:
</p>
<table><tr><td> </td><td><pre class="example"># Start counting PTS from zero
asetpts=expr=PTS-STARTPTS
# Generate timestamps by counting samples
asetpts=expr=N/SR/TB
# Generate timestamps from a "live source" and rebase onto the current timebase
asetpts='(RTCTIME - RTCSTART) / (TB * 1000000)"
</pre></td></tr></table>
<a name="asettb"></a>
<h2 class="section"><a href="avconv.html#toc-asettb">21.5 asettb</a></h2>
<p>Set the timebase to use for the output frames timestamps.
It is mainly useful for testing timebase configuration.
</p>
<p>This filter accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>expr</samp>’</dt>
<dd><p>The expression which is evaluated into the output timebase.
</p>
</dd>
</dl>
<p>The expression can contain the constants <var>PI</var>, <var>E</var>, <var>PHI</var>, <var>AVTB</var> (the
default timebase), <var>intb</var> (the input timebase), and <var>sr</var> (the sample rate,
audio only).
</p>
<p>The default value for the input is <var>intb</var>.
</p>
<p>Some examples:
</p>
<table><tr><td> </td><td><pre class="example"># Set the timebase to 1/25:
settb=1/25
# Set the timebase to 1/10:
settb=0.1
# Set the timebase to 1001/1000:
settb=1+0.001
# Set the timebase to 2*intb:
settb=2*intb
# Set the default timebase value:
settb=AVTB
# Set the timebase to twice the sample rate:
asettb=sr*2
</pre></td></tr></table>
<a name="ashowinfo"></a>
<h2 class="section"><a href="avconv.html#toc-ashowinfo">21.6 ashowinfo</a></h2>
<p>Show a line containing various information for each input audio frame.
The input audio is not modified.
</p>
<p>The shown line contains a sequence of key/value pairs of the form
<var>key</var>:<var>value</var>.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>n</samp>’</dt>
<dd><p>The (sequential) number of the input frame, starting from 0.
</p>
</dd>
<dt> ‘<samp>pts</samp>’</dt>
<dd><p>The presentation timestamp of the input frame, in time base units; the time base
depends on the filter input pad, and is usually 1/<var>sample_rate</var>.
</p>
</dd>
<dt> ‘<samp>pts_time</samp>’</dt>
<dd><p>The presentation timestamp of the input frame in seconds.
</p>
</dd>
<dt> ‘<samp>fmt</samp>’</dt>
<dd><p>The sample format.
</p>
</dd>
<dt> ‘<samp>chlayout</samp>’</dt>
<dd><p>The channel layout.
</p>
</dd>
<dt> ‘<samp>rate</samp>’</dt>
<dd><p>The sample rate for the audio frame.
</p>
</dd>
<dt> ‘<samp>nb_samples</samp>’</dt>
<dd><p>The number of samples (per channel) in the frame.
</p>
</dd>
<dt> ‘<samp>checksum</samp>’</dt>
<dd><p>The Adler-32 checksum (printed in hexadecimal) of the audio data. For planar
audio, the data is treated as if all the planes were concatenated.
</p>
</dd>
<dt> ‘<samp>plane_checksums</samp>’</dt>
<dd><p>A list of Adler-32 checksums for each data plane.
</p></dd>
</dl>
<a name="asplit"></a>
<h2 class="section"><a href="avconv.html#toc-asplit">21.7 asplit</a></h2>
<p>Split input audio into several identical outputs.
</p>
<p>It accepts a single parameter, which specifies the number of outputs. If
unspecified, it defaults to 2.
</p>
<p>For example,
</p><table><tr><td> </td><td><pre class="example">avconv -i INPUT -filter_complex asplit=5 OUTPUT
</pre></td></tr></table>
<p>will create 5 copies of the input audio.
</p>
<a name="asyncts"></a>
<h2 class="section"><a href="avconv.html#toc-asyncts">21.8 asyncts</a></h2>
<p>Synchronize audio data with timestamps by squeezing/stretching it and/or
dropping samples/adding silence when needed.
</p>
<p>It accepts the following parameters:
</p><dl compact="compact">
<dt> ‘<samp>compensate</samp>’</dt>
<dd><p>Enable stretching/squeezing the data to make it match the timestamps. Disabled
by default. When disabled, time gaps are covered with silence.
</p>
</dd>
<dt> ‘<samp>min_delta</samp>’</dt>
<dd><p>The minimum difference between timestamps and audio data (in seconds) to trigger
adding/dropping samples. The default value is 0.1. If you get an imperfect
sync with this filter, try setting this parameter to 0.
</p>
</dd>
<dt> ‘<samp>max_comp</samp>’</dt>
<dd><p>The maximum compensation in samples per second. Only relevant with compensate=1.
The default value is 500.
</p>
</dd>
<dt> ‘<samp>first_pts</samp>’</dt>
<dd><p>Assume that the first PTS should be this value. The time base is 1 / sample
rate. This allows for padding/trimming at the start of the stream. By default,
no assumption is made about the first frame’s expected PTS, so no padding or
trimming is done. For example, this could be set to 0 to pad the beginning with
silence if an audio stream starts after the video stream or to trim any samples
with a negative PTS due to encoder delay.
</p>
</dd>
</dl>
<a name="atrim"></a>
<h2 class="section"><a href="avconv.html#toc-atrim">21.9 atrim</a></h2>
<p>Trim the input so that the output contains one continuous subpart of the input.
</p>
<p>It accepts the following parameters:
</p><dl compact="compact">
<dt> ‘<samp>start</samp>’</dt>
<dd><p>Timestamp (in seconds) of the start of the section to keep. I.e. the audio
sample with the timestamp <var>start</var> will be the first sample in the output.
</p>
</dd>
<dt> ‘<samp>end</samp>’</dt>
<dd><p>Timestamp (in seconds) of the first audio sample that will be dropped. I.e. the
audio sample immediately preceding the one with the timestamp <var>end</var> will be
the last sample in the output.
</p>
</dd>
<dt> ‘<samp>start_pts</samp>’</dt>
<dd><p>Same as <var>start</var>, except this option sets the start timestamp in samples
instead of seconds.
</p>
</dd>
<dt> ‘<samp>end_pts</samp>’</dt>
<dd><p>Same as <var>end</var>, except this option sets the end timestamp in samples instead
of seconds.
</p>
</dd>
<dt> ‘<samp>duration</samp>’</dt>
<dd><p>The maximum duration of the output in seconds.
</p>
</dd>
<dt> ‘<samp>start_sample</samp>’</dt>
<dd><p>The number of the first sample that should be output.
</p>
</dd>
<dt> ‘<samp>end_sample</samp>’</dt>
<dd><p>The number of the first sample that should be dropped.
</p></dd>
</dl>
<p>Note that the first two sets of the start/end options and the ‘<samp>duration</samp>’
option look at the frame timestamp, while the _sample options simply count the
samples that pass through the filter. So start/end_pts and start/end_sample will
give different results when the timestamps are wrong, inexact or do not start at
zero. Also note that this filter does not modify the timestamps. If you wish
to have the output timestamps start at zero, insert the asetpts filter after the
atrim filter.
</p>
<p>If multiple start or end options are set, this filter tries to be greedy and
keep all samples that match at least one of the specified constraints. To keep
only the part that matches all the constraints at once, chain multiple atrim
filters.
</p>
<p>The defaults are such that all the input is kept. So it is possible to set e.g.
just the end values to keep everything before the specified time.
</p>
<p>Examples:
</p><ul>
<li>
Drop everything except the second minute of input:
<table><tr><td> </td><td><pre class="example">avconv -i INPUT -af atrim=60:120
</pre></td></tr></table>
</li><li>
Keep only the first 1000 samples:
<table><tr><td> </td><td><pre class="example">avconv -i INPUT -af atrim=end_sample=1000
</pre></td></tr></table>
</li></ul>
<a name="bs2b"></a>
<h2 class="section"><a href="avconv.html#toc-bs2b">21.10 bs2b</a></h2>
<p>Bauer stereo to binaural transformation, which improves headphone listening of
stereo audio records.
</p>
<p>It accepts the following parameters:
</p><dl compact="compact">
<dt> ‘<samp>profile</samp>’</dt>
<dd><p>Pre-defined crossfeed level.
</p><dl compact="compact">
<dt> ‘<samp>default</samp>’</dt>
<dd><p>Default level (fcut=700, feed=50).
</p>
</dd>
<dt> ‘<samp>cmoy</samp>’</dt>
<dd><p>Chu Moy circuit (fcut=700, feed=60).
</p>
</dd>
<dt> ‘<samp>jmeier</samp>’</dt>
<dd><p>Jan Meier circuit (fcut=650, feed=95).
</p>
</dd>
</dl>
</dd>
<dt> ‘<samp>fcut</samp>’</dt>
<dd><p>Cut frequency (in Hz).
</p>
</dd>
<dt> ‘<samp>feed</samp>’</dt>
<dd><p>Feed level (in Hz).
</p>
</dd>
</dl>
<a name="channelsplit"></a>
<h2 class="section"><a href="avconv.html#toc-channelsplit">21.11 channelsplit</a></h2>
<p>Split each channel from an input audio stream into a separate output stream.
</p>
<p>It accepts the following parameters:
</p><dl compact="compact">
<dt> ‘<samp>channel_layout</samp>’</dt>
<dd><p>The channel layout of the input stream. The default is "stereo".
</p></dd>
</dl>
<p>For example, assuming a stereo input MP3 file,
</p><table><tr><td> </td><td><pre class="example">avconv -i in.mp3 -filter_complex channelsplit out.mkv
</pre></td></tr></table>
<p>will create an output Matroska file with two audio streams, one containing only
the left channel and the other the right channel.
</p>
<p>Split a 5.1 WAV file into per-channel files:
</p><table><tr><td> </td><td><pre class="example">avconv -i in.wav -filter_complex
'channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR]'
-map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]'
front_center.wav -map '[LFE]' lfe.wav -map '[SL]' side_left.wav -map '[SR]'
side_right.wav
</pre></td></tr></table>
<a name="channelmap"></a>
<h2 class="section"><a href="avconv.html#toc-channelmap">21.12 channelmap</a></h2>
<p>Remap input channels to new locations.
</p>
<p>It accepts the following parameters:
</p><dl compact="compact">
<dt> ‘<samp>channel_layout</samp>’</dt>
<dd><p>The channel layout of the output stream.
</p>
</dd>
<dt> ‘<samp>map</samp>’</dt>
<dd><p>Map channels from input to output. The argument is a ’|’-separated list of
mappings, each in the <code><var>in_channel</var>-<var>out_channel</var></code> or
<var>in_channel</var> form. <var>in_channel</var> can be either the name of the input
channel (e.g. FL for front left) or its index in the input channel layout.
<var>out_channel</var> is the name of the output channel or its index in the output
channel layout. If <var>out_channel</var> is not given then it is implicitly an
index, starting with zero and increasing by one for each mapping.
</p></dd>
</dl>
<p>If no mapping is present, the filter will implicitly map input channels to
output channels, preserving indices.
</p>
<p>For example, assuming a 5.1+downmix input MOV file,
</p><table><tr><td> </td><td><pre class="example">avconv -i in.mov -filter 'channelmap=map=DL-FL|DR-FR' out.wav
</pre></td></tr></table>
<p>will create an output WAV file tagged as stereo from the downmix channels of
the input.
</p>
<p>To fix a 5.1 WAV improperly encoded in AAC’s native channel order
</p><table><tr><td> </td><td><pre class="example">avconv -i in.wav -filter 'channelmap=1|2|0|5|3|4:channel_layout=5.1' out.wav
</pre></td></tr></table>
<a name="compand"></a>
<h2 class="section"><a href="avconv.html#toc-compand">21.13 compand</a></h2>
<p>Compress or expand the audio’s dynamic range.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>attacks</samp>’</dt>
<dt> ‘<samp>decays</samp>’</dt>
<dd><p>A list of times in seconds for each channel over which the instantaneous level
of the input signal is averaged to determine its volume. <var>attacks</var> refers to
increase of volume and <var>decays</var> refers to decrease of volume. For most
situations, the attack time (response to the audio getting louder) should be
shorter than the decay time, because the human ear is more sensitive to sudden
loud audio than sudden soft audio. A typical value for attack is 0.3 seconds and
a typical value for decay is 0.8 seconds.
</p>
</dd>
<dt> ‘<samp>points</samp>’</dt>
<dd><p>A list of points for the transfer function, specified in dB relative to the
maximum possible signal amplitude. Each key points list must be defined using
the following syntax: <code>x0/y0|x1/y1|x2/y2|....</code>
</p>
<p>The input values must be in strictly increasing order but the transfer function
does not have to be monotonically rising. The point <code>0/0</code> is assumed but
may be overridden (by <code>0/out-dBn</code>). Typical values for the transfer
function are <code>-70/-70|-60/-20</code>.
</p>
</dd>
<dt> ‘<samp>soft-knee</samp>’</dt>
<dd><p>Set the curve radius in dB for all joints. It defaults to 0.01.
</p>
</dd>
<dt> ‘<samp>gain</samp>’</dt>
<dd><p>Set the additional gain in dB to be applied at all points on the transfer
function. This allows for easy adjustment of the overall gain.
It defaults to 0.
</p>
</dd>
<dt> ‘<samp>volume</samp>’</dt>
<dd><p>Set an initial volume, in dB, to be assumed for each channel when filtering
starts. This permits the user to supply a nominal level initially, so that, for
example, a very large gain is not applied to initial signal levels before the
companding has begun to operate. A typical value for audio which is initially
quiet is -90 dB. It defaults to 0.
</p>
</dd>
<dt> ‘<samp>delay</samp>’</dt>
<dd><p>Set a delay, in seconds. The input audio is analyzed immediately, but audio is
delayed before being fed to the volume adjuster. Specifying a delay
approximately equal to the attack/decay times allows the filter to effectively
operate in predictive rather than reactive mode. It defaults to 0.
</p>
</dd>
</dl>
<a name="Examples"></a>
<h3 class="subsection"><a href="avconv.html#toc-Examples">21.13.1 Examples</a></h3>
<ul>
<li>
Make music with both quiet and loud passages suitable for listening to in a
noisy environment:
<table><tr><td> </td><td><pre class="example">compand=.3|.3:1|1:-90/-60|-60/-40|-40/-30|-20/-20:6:0:-90:0.2
</pre></td></tr></table>
</li><li>
A noise gate for when the noise is at a lower level than the signal:
<table><tr><td> </td><td><pre class="example">compand=.1|.1:.2|.2:-900/-900|-50.1/-900|-50/-50:.01:0:-90:.1
</pre></td></tr></table>
</li><li>
Here is another noise gate, this time for when the noise is at a higher level
than the signal (making it, in some ways, similar to squelch):
<table><tr><td> </td><td><pre class="example">compand=.1|.1:.1|.1:-45.1/-45.1|-45/-900|0/-900:.01:45:-90:.1
</pre></td></tr></table>
</li></ul>
<a name="join"></a>
<h2 class="section"><a href="avconv.html#toc-join">21.14 join</a></h2>
<p>Join multiple input streams into one multi-channel stream.
</p>
<p>It accepts the following parameters:
</p><dl compact="compact">
<dt> ‘<samp>inputs</samp>’</dt>
<dd><p>The number of input streams. It defaults to 2.
</p>
</dd>
<dt> ‘<samp>channel_layout</samp>’</dt>
<dd><p>The desired output channel layout. It defaults to stereo.
</p>
</dd>
<dt> ‘<samp>map</samp>’</dt>
<dd><p>Map channels from inputs to output. The argument is a ’|’-separated list of
mappings, each in the <code><var>input_idx</var>.<var>in_channel</var>-<var>out_channel</var></code>
form. <var>input_idx</var> is the 0-based index of the input stream. <var>in_channel</var>
can be either the name of the input channel (e.g. FL for front left) or its
index in the specified input stream. <var>out_channel</var> is the name of the output
channel.
</p></dd>
</dl>
<p>The filter will attempt to guess the mappings when they are not specified
explicitly. It does so by first trying to find an unused matching input channel
and if that fails it picks the first unused input channel.
</p>
<p>Join 3 inputs (with properly set channel layouts):
</p><table><tr><td> </td><td><pre class="example">avconv -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex join=inputs=3 OUTPUT
</pre></td></tr></table>
<p>Build a 5.1 output from 6 single-channel streams:
</p><table><tr><td> </td><td><pre class="example">avconv -i fl -i fr -i fc -i sl -i sr -i lfe -filter_complex
'join=inputs=6:channel_layout=5.1:map=0.0-FL|1.0-FR|2.0-FC|3.0-SL|4.0-SR|5.0-LFE'
out
</pre></td></tr></table>
<a name="resample"></a>
<h2 class="section"><a href="avconv.html#toc-resample">21.15 resample</a></h2>
<p>Convert the audio sample format, sample rate and channel layout. It is
not meant to be used directly; it is inserted automatically by libavfilter
whenever conversion is needed. Use the <var>aformat</var> filter to force a specific
conversion.
</p>
<a name="volume"></a>
<h2 class="section"><a href="avconv.html#toc-volume">21.16 volume</a></h2>
<p>Adjust the input audio volume.
</p>
<p>It accepts the following parameters:
</p><dl compact="compact">
<dt> ‘<samp>volume</samp>’</dt>
<dd><p>This expresses how the audio volume will be increased or decreased.
</p>
<p>Output values are clipped to the maximum value.
</p>
<p>The output audio volume is given by the relation:
</p><table><tr><td> </td><td><pre class="example"><var>output_volume</var> = <var>volume</var> * <var>input_volume</var>
</pre></td></tr></table>
<p>The default value for <var>volume</var> is 1.0.
</p>
</dd>
<dt> ‘<samp>precision</samp>’</dt>
<dd><p>This parameter represents the mathematical precision.
</p>
<p>It determines which input sample formats will be allowed, which affects the
precision of the volume scaling.
</p>
<dl compact="compact">
<dt> ‘<samp>fixed</samp>’</dt>
<dd><p>8-bit fixed-point; this limits input sample format to U8, S16, and S32.
</p></dd>
<dt> ‘<samp>float</samp>’</dt>
<dd><p>32-bit floating-point; this limits input sample format to FLT. (default)
</p></dd>
<dt> ‘<samp>double</samp>’</dt>
<dd><p>64-bit floating-point; this limits input sample format to DBL.
</p></dd>
</dl>
</dd>
<dt> ‘<samp>replaygain</samp>’</dt>
<dd><p>Choose the behaviour on encountering ReplayGain side data in input frames.
</p>
<dl compact="compact">
<dt> ‘<samp>drop</samp>’</dt>
<dd><p>Remove ReplayGain side data, ignoring its contents (the default).
</p>
</dd>
<dt> ‘<samp>ignore</samp>’</dt>
<dd><p>Ignore ReplayGain side data, but leave it in the frame.
</p>
</dd>
<dt> ‘<samp>track</samp>’</dt>
<dd><p>Prefer the track gain, if present.
</p>
</dd>
<dt> ‘<samp>album</samp>’</dt>
<dd><p>Prefer the album gain, if present.
</p></dd>
</dl>
</dd>
<dt> ‘<samp>replaygain_preamp</samp>’</dt>
<dd><p>Pre-amplification gain in dB to apply to the selected replaygain gain.
</p>
<p>Default value for <var>replaygain_preamp</var> is 0.0.
</p>
</dd>
<dt> ‘<samp>replaygain_noclip</samp>’</dt>
<dd><p>Prevent clipping by limiting the gain applied.
</p>
<p>Default value for <var>replaygain_noclip</var> is 1.
</p>
</dd>
</dl>
<a name="Examples-2"></a>
<h3 class="subsection"><a href="avconv.html#toc-Examples-2">21.16.1 Examples</a></h3>
<ul>
<li>
Halve the input audio volume:
<table><tr><td> </td><td><pre class="example">volume=volume=0.5
volume=volume=1/2
volume=volume=-6.0206dB
</pre></td></tr></table>
</li><li>
Increase input audio power by 6 decibels using fixed-point precision:
<table><tr><td> </td><td><pre class="example">volume=volume=6dB:precision=fixed
</pre></td></tr></table>
</li></ul>
<a name="Audio-Sources"></a>
<h1 class="chapter"><a href="avconv.html#toc-Audio-Sources">22. Audio Sources</a></h1>
<p>Below is a description of the currently available audio sources.
</p>
<a name="anullsrc"></a>
<h2 class="section"><a href="avconv.html#toc-anullsrc">22.1 anullsrc</a></h2>
<p>The null audio source; it never returns audio frames. It is mainly useful as a
template and for use in analysis / debugging tools.
</p>
<p>It accepts, as an optional parameter, a string of the form
<var>sample_rate</var>:<var>channel_layout</var>.
</p>
<p><var>sample_rate</var> specifies the sample rate, and defaults to 44100.
</p>
<p><var>channel_layout</var> specifies the channel layout, and can be either an
integer or a string representing a channel layout. The default value
of <var>channel_layout</var> is 3, which corresponds to CH_LAYOUT_STEREO.
</p>
<p>Check the channel_layout_map definition in
‘<tt>libavutil/channel_layout.c</tt>’ for the mapping between strings and
channel layout values.
</p>
<p>Some examples:
</p><table><tr><td> </td><td><pre class="example"># Set the sample rate to 48000 Hz and the channel layout to CH_LAYOUT_MONO
anullsrc=48000:4
# The same as above
anullsrc=48000:mono
</pre></td></tr></table>
<a name="abuffer"></a>
<h2 class="section"><a href="avconv.html#toc-abuffer">22.2 abuffer</a></h2>
<p>Buffer audio frames, and make them available to the filter chain.
</p>
<p>This source is not intended to be part of user-supplied graph descriptions; it
is for insertion by calling programs, through the interface defined in
‘<tt>libavfilter/buffersrc.h</tt>’.
</p>
<p>It accepts the following parameters:
</p><dl compact="compact">
<dt> ‘<samp>time_base</samp>’</dt>
<dd><p>The timebase which will be used for timestamps of submitted frames. It must be
either a floating-point number or in <var>numerator</var>/<var>denominator</var> form.
</p>
</dd>
<dt> ‘<samp>sample_rate</samp>’</dt>
<dd><p>The audio sample rate.
</p>
</dd>
<dt> ‘<samp>sample_fmt</samp>’</dt>
<dd><p>The name of the sample format, as returned by <code>av_get_sample_fmt_name()</code>.
</p>
</dd>
<dt> ‘<samp>channel_layout</samp>’</dt>
<dd><p>The channel layout of the audio data, in the form that can be accepted by
<code>av_get_channel_layout()</code>.
</p></dd>
</dl>
<p>All the parameters need to be explicitly defined.
</p>
<a name="Audio-Sinks"></a>
<h1 class="chapter"><a href="avconv.html#toc-Audio-Sinks">23. Audio Sinks</a></h1>
<p>Below is a description of the currently available audio sinks.
</p>
<a name="anullsink"></a>
<h2 class="section"><a href="avconv.html#toc-anullsink">23.1 anullsink</a></h2>
<p>Null audio sink; do absolutely nothing with the input audio. It is
mainly useful as a template and for use in analysis / debugging
tools.
</p>
<a name="abuffersink"></a>
<h2 class="section"><a href="avconv.html#toc-abuffersink">23.2 abuffersink</a></h2>
<p>This sink is intended for programmatic use. Frames that arrive on this sink can
be retrieved by the calling program, using the interface defined in
‘<tt>libavfilter/buffersink.h</tt>’.
</p>
<p>It does not accept any parameters.
</p>
<a name="Video-Filters"></a>
<h1 class="chapter"><a href="avconv.html#toc-Video-Filters">24. Video Filters</a></h1>
<p>When you configure your Libav build, you can disable any of the
existing filters using –disable-filters.
The configure output will show the video filters included in your
build.
</p>
<p>Below is a description of the currently available video filters.
</p>
<a name="blackframe"></a>
<h2 class="section"><a href="avconv.html#toc-blackframe">24.1 blackframe</a></h2>
<p>Detect frames that are (almost) completely black. Can be useful to
detect chapter transitions or commercials. Output lines consist of
the frame number of the detected frame, the percentage of blackness,
the position in the file if known or -1 and the timestamp in seconds.
</p>
<p>In order to display the output lines, you need to set the loglevel at
least to the AV_LOG_INFO value.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>amount</samp>’</dt>
<dd><p>The percentage of the pixels that have to be below the threshold; it defaults to
98.
</p>
</dd>
<dt> ‘<samp>threshold</samp>’</dt>
<dd><p>The threshold below which a pixel value is considered black; it defaults to 32.
</p>
</dd>
</dl>
<a name="boxblur"></a>
<h2 class="section"><a href="avconv.html#toc-boxblur">24.2 boxblur</a></h2>
<p>Apply a boxblur algorithm to the input video.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>luma_radius</samp>’</dt>
<dt> ‘<samp>luma_power</samp>’</dt>
<dt> ‘<samp>chroma_radius</samp>’</dt>
<dt> ‘<samp>chroma_power</samp>’</dt>
<dt> ‘<samp>alpha_radius</samp>’</dt>
<dt> ‘<samp>alpha_power</samp>’</dt>
</dl>
<p>The chroma and alpha parameters are optional. If not specified, they default
to the corresponding values set for <var>luma_radius</var> and
<var>luma_power</var>.
</p>
<p><var>luma_radius</var>, <var>chroma_radius</var>, and <var>alpha_radius</var> represent
the radius in pixels of the box used for blurring the corresponding
input plane. They are expressions, and can contain the following
constants:
</p><dl compact="compact">
<dt> ‘<samp>w, h</samp>’</dt>
<dd><p>The input width and height in pixels.
</p>
</dd>
<dt> ‘<samp>cw, ch</samp>’</dt>
<dd><p>The input chroma image width and height in pixels.
</p>
</dd>
<dt> ‘<samp>hsub, vsub</samp>’</dt>
<dd><p>The horizontal and vertical chroma subsample values. For example, for the
pixel format "yuv422p", <var>hsub</var> is 2 and <var>vsub</var> is 1.
</p></dd>
</dl>
<p>The radius must be a non-negative number, and must not be greater than
the value of the expression <code>min(w,h)/2</code> for the luma and alpha planes,
and of <code>min(cw,ch)/2</code> for the chroma planes.
</p>
<p><var>luma_power</var>, <var>chroma_power</var>, and <var>alpha_power</var> represent
how many times the boxblur filter is applied to the corresponding
plane.
</p>
<p>Some examples:
</p>
<ul>
<li>
Apply a boxblur filter with the luma, chroma, and alpha radii
set to 2:
<table><tr><td> </td><td><pre class="example">boxblur=luma_radius=2:luma_power=1
</pre></td></tr></table>
</li><li>
Set the luma radius to 2, and alpha and chroma radius to 0:
<table><tr><td> </td><td><pre class="example">boxblur=2:1:0:0:0:0
</pre></td></tr></table>
</li><li>
Set the luma and chroma radii to a fraction of the video dimension:
<table><tr><td> </td><td><pre class="example">boxblur=luma_radius=min(h\,w)/10:luma_power=1:chroma_radius=min(cw\,ch)/10:chroma_power=1
</pre></td></tr></table>
</li></ul>
<a name="copy"></a>
<h2 class="section"><a href="avconv.html#toc-copy">24.3 copy</a></h2>
<p>Copy the input source unchanged to the output. This is mainly useful for
testing purposes.
</p>
<a name="crop"></a>
<h2 class="section"><a href="avconv.html#toc-crop">24.4 crop</a></h2>
<p>Crop the input video to given dimensions.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>out_w</samp>’</dt>
<dd><p>The width of the output video.
</p>
</dd>
<dt> ‘<samp>out_h</samp>’</dt>
<dd><p>The height of the output video.
</p>
</dd>
<dt> ‘<samp>x</samp>’</dt>
<dd><p>The horizontal position, in the input video, of the left edge of the output
video.
</p>
</dd>
<dt> ‘<samp>y</samp>’</dt>
<dd><p>The vertical position, in the input video, of the top edge of the output video.
</p>
</dd>
</dl>
<p>The parameters are expressions containing the following constants:
</p>
<dl compact="compact">
<dt> ‘<samp>E, PI, PHI</samp>’</dt>
<dd><p>These are approximated values for the mathematical constants e
(Euler’s number), pi (Greek pi), and phi (the golden ratio).
</p>
</dd>
<dt> ‘<samp>x, y</samp>’</dt>
<dd><p>The computed values for <var>x</var> and <var>y</var>. They are evaluated for
each new frame.
</p>
</dd>
<dt> ‘<samp>in_w, in_h</samp>’</dt>
<dd><p>The input width and height.
</p>
</dd>
<dt> ‘<samp>iw, ih</samp>’</dt>
<dd><p>These are the same as <var>in_w</var> and <var>in_h</var>.
</p>
</dd>
<dt> ‘<samp>out_w, out_h</samp>’</dt>
<dd><p>The output (cropped) width and height.
</p>
</dd>
<dt> ‘<samp>ow, oh</samp>’</dt>
<dd><p>These are the same as <var>out_w</var> and <var>out_h</var>.
</p>
</dd>
<dt> ‘<samp>n</samp>’</dt>
<dd><p>The number of the input frame, starting from 0.
</p>
</dd>
<dt> ‘<samp>t</samp>’</dt>
<dd><p>The timestamp expressed in seconds. It’s NAN if the input timestamp is unknown.
</p>
</dd>
</dl>
<p>The <var>out_w</var> and <var>out_h</var> parameters specify the expressions for
the width and height of the output (cropped) video. They are only
evaluated during the configuration of the filter.
</p>
<p>The default value of <var>out_w</var> is "in_w", and the default value of
<var>out_h</var> is "in_h".
</p>
<p>The expression for <var>out_w</var> may depend on the value of <var>out_h</var>,
and the expression for <var>out_h</var> may depend on <var>out_w</var>, but they
cannot depend on <var>x</var> and <var>y</var>, as <var>x</var> and <var>y</var> are
evaluated after <var>out_w</var> and <var>out_h</var>.
</p>
<p>The <var>x</var> and <var>y</var> parameters specify the expressions for the
position of the top-left corner of the output (non-cropped) area. They
are evaluated for each frame. If the evaluated value is not valid, it
is approximated to the nearest valid value.
</p>
<p>The default value of <var>x</var> is "(in_w-out_w)/2", and the default
value for <var>y</var> is "(in_h-out_h)/2", which set the cropped area at
the center of the input image.
</p>
<p>The expression for <var>x</var> may depend on <var>y</var>, and the expression
for <var>y</var> may depend on <var>x</var>.
</p>
<p>Some examples:
</p><table><tr><td> </td><td><pre class="example"># Crop the central input area with size 100x100
crop=out_w=100:out_h=100
# Crop the central input area with size 2/3 of the input video
"crop=out_w=2/3*in_w:out_h=2/3*in_h"
# Crop the input video central square
crop=out_w=in_h
# Delimit the rectangle with the top-left corner placed at position
# 100:100 and the right-bottom corner corresponding to the right-bottom
# corner of the input image
crop=out_w=in_w-100:out_h=in_h-100:x=100:y=100
# Crop 10 pixels from the left and right borders, and 20 pixels from
# the top and bottom borders
"crop=out_w=in_w-2*10:out_h=in_h-2*20"
# Keep only the bottom right quarter of the input image
"crop=out_w=in_w/2:out_h=in_h/2:x=in_w/2:y=in_h/2"
# Crop height for getting Greek harmony
"crop=out_w=in_w:out_h=1/PHI*in_w"
# Trembling effect
"crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(n/10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(n/7)"
# Erratic camera effect depending on timestamp
"crop=out_w=in_w/2:out_h=in_h/2:x=(in_w-out_w)/2+((in_w-out_w)/2)*sin(t*10):y=(in_h-out_h)/2 +((in_h-out_h)/2)*sin(t*13)"
# Set x depending on the value of y
"crop=in_w/2:in_h/2:y:10+10*sin(n/10)"
</pre></td></tr></table>
<a name="cropdetect"></a>
<h2 class="section"><a href="avconv.html#toc-cropdetect">24.5 cropdetect</a></h2>
<p>Auto-detect the crop size.
</p>
<p>It calculates the necessary cropping parameters and prints the
recommended parameters via the logging system. The detected dimensions
correspond to the non-black area of the input video.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>limit</samp>’</dt>
<dd><p>The threshold, an optional parameter between nothing (0) and
everything (255). It defaults to 24.
</p>
</dd>
<dt> ‘<samp>round</samp>’</dt>
<dd><p>The value which the width/height should be divisible by. It defaults to
16. The offset is automatically adjusted to center the video. Use 2 to
get only even dimensions (needed for 4:2:2 video). 16 is best when
encoding to most video codecs.
</p>
</dd>
<dt> ‘<samp>reset</samp>’</dt>
<dd><p>A counter that determines how many frames cropdetect will reset
the previously detected largest video area after. It will then start over
and detect the current optimal crop area. It defaults to 0.
</p>
<p>This can be useful when channel logos distort the video area. 0
indicates ’never reset’, and returns the largest area encountered during
playback.
</p></dd>
</dl>
<a name="delogo"></a>
<h2 class="section"><a href="avconv.html#toc-delogo">24.6 delogo</a></h2>
<p>Suppress a TV station logo by a simple interpolation of the surrounding
pixels. Just set a rectangle covering the logo and watch it disappear
(and sometimes something even uglier appear - your mileage may vary).
</p>
<p>It accepts the following parameters:
</p><dl compact="compact">
<dt> ‘<samp>x, y</samp>’</dt>
<dd><p>Specify the top left corner coordinates of the logo. They must be
specified.
</p>
</dd>
<dt> ‘<samp>w, h</samp>’</dt>
<dd><p>Specify the width and height of the logo to clear. They must be
specified.
</p>
</dd>
<dt> ‘<samp>band, t</samp>’</dt>
<dd><p>Specify the thickness of the fuzzy edge of the rectangle (added to
<var>w</var> and <var>h</var>). The default value is 4.
</p>
</dd>
<dt> ‘<samp>show</samp>’</dt>
<dd><p>When set to 1, a green rectangle is drawn on the screen to simplify
finding the right <var>x</var>, <var>y</var>, <var>w</var>, <var>h</var> parameters, and
<var>band</var> is set to 4. The default value is 0.
</p>
</dd>
</dl>
<p>An example:
</p>
<ul>
<li>
Set a rectangle covering the area with top left corner coordinates 0,0
and size 100x77, and a band of size 10:
<table><tr><td> </td><td><pre class="example">delogo=x=0:y=0:w=100:h=77:band=10
</pre></td></tr></table>
</li></ul>
<a name="drawbox"></a>
<h2 class="section"><a href="avconv.html#toc-drawbox">24.7 drawbox</a></h2>
<p>Draw a colored box on the input image.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>x, y</samp>’</dt>
<dd><p>Specify the top left corner coordinates of the box. It defaults to 0.
</p>
</dd>
<dt> ‘<samp>width, height</samp>’</dt>
<dd><p>Specify the width and height of the box; if 0 they are interpreted as
the input width and height. It defaults to 0.
</p>
</dd>
<dt> ‘<samp>color</samp>’</dt>
<dd><p>Specify the color of the box to write. It can be the name of a color
(case insensitive match) or a 0xRRGGBB[AA] sequence.
</p></dd>
</dl>
<p>Some examples:
</p><table><tr><td> </td><td><pre class="example"># Draw a black box around the edge of the input image
drawbox
# Draw a box with color red and an opacity of 50%
drawbox=x=10:y=20:width=200:height=60:color=red@0.5"
</pre></td></tr></table>
<a name="drawtext"></a>
<h2 class="section"><a href="avconv.html#toc-drawtext">24.8 drawtext</a></h2>
<p>Draw a text string or text from a specified file on top of a video, using the
libfreetype library.
</p>
<p>To enable compilation of this filter, you need to configure Libav with
<code>--enable-libfreetype</code>.
To enable default font fallback and the <var>font</var> option you need to
configure Libav with <code>--enable-libfontconfig</code>.
</p>
<p>The filter also recognizes strftime() sequences in the provided text
and expands them accordingly. Check the documentation of strftime().
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>font</samp>’</dt>
<dd><p>The font family to be used for drawing text. By default Sans.
</p>
</dd>
<dt> ‘<samp>fontfile</samp>’</dt>
<dd><p>The font file to be used for drawing text. The path must be included.
This parameter is mandatory if the fontconfig support is disabled.
</p>
</dd>
<dt> ‘<samp>text</samp>’</dt>
<dd><p>The text string to be drawn. The text must be a sequence of UTF-8
encoded characters.
This parameter is mandatory if no file is specified with the parameter
<var>textfile</var>.
</p>
</dd>
<dt> ‘<samp>textfile</samp>’</dt>
<dd><p>A text file containing text to be drawn. The text must be a sequence
of UTF-8 encoded characters.
</p>
<p>This parameter is mandatory if no text string is specified with the
parameter <var>text</var>.
</p>
<p>If both text and textfile are specified, an error is thrown.
</p>
</dd>
<dt> ‘<samp>x, y</samp>’</dt>
<dd><p>The offsets where text will be drawn within the video frame.
It is relative to the top/left border of the output image.
They accept expressions similar to the <a href="#overlay">overlay</a> filter:
</p><dl compact="compact">
<dt> ‘<samp>x, y</samp>’</dt>
<dd><p>The computed values for <var>x</var> and <var>y</var>. They are evaluated for
each new frame.
</p>
</dd>
<dt> ‘<samp>main_w, main_h</samp>’</dt>
<dd><p>The main input width and height.
</p>
</dd>
<dt> ‘<samp>W, H</samp>’</dt>
<dd><p>These are the same as <var>main_w</var> and <var>main_h</var>.
</p>
</dd>
<dt> ‘<samp>text_w, text_h</samp>’</dt>
<dd><p>The rendered text’s width and height.
</p>
</dd>
<dt> ‘<samp>w, h</samp>’</dt>
<dd><p>These are the same as <var>text_w</var> and <var>text_h</var>.
</p>
</dd>
<dt> ‘<samp>n</samp>’</dt>
<dd><p>The number of frames processed, starting from 0.
</p>
</dd>
<dt> ‘<samp>t</samp>’</dt>
<dd><p>The timestamp, expressed in seconds. It’s NAN if the input timestamp is unknown.
</p>
</dd>
</dl>
<p>The default value of <var>x</var> and <var>y</var> is 0.
</p>
</dd>
<dt> ‘<samp>fontsize</samp>’</dt>
<dd><p>The font size to be used for drawing text.
The default value of <var>fontsize</var> is 16.
</p>
</dd>
<dt> ‘<samp>fontcolor</samp>’</dt>
<dd><p>The color to be used for drawing fonts.
It is either a string (e.g. "red"), or in 0xRRGGBB[AA] format
(e.g. "0xff000033"), possibly followed by an alpha specifier.
The default value of <var>fontcolor</var> is "black".
</p>
</dd>
<dt> ‘<samp>boxcolor</samp>’</dt>
<dd><p>The color to be used for drawing box around text.
It is either a string (e.g. "yellow") or in 0xRRGGBB[AA] format
(e.g. "0xff00ff"), possibly followed by an alpha specifier.
The default value of <var>boxcolor</var> is "white".
</p>
</dd>
<dt> ‘<samp>box</samp>’</dt>
<dd><p>Used to draw a box around text using the background color.
The value must be either 1 (enable) or 0 (disable).
The default value of <var>box</var> is 0.
</p>
</dd>
<dt> ‘<samp>shadowx, shadowy</samp>’</dt>
<dd><p>The x and y offsets for the text shadow position with respect to the
position of the text. They can be either positive or negative
values. The default value for both is "0".
</p>
</dd>
<dt> ‘<samp>shadowcolor</samp>’</dt>
<dd><p>The color to be used for drawing a shadow behind the drawn text. It
can be a color name (e.g. "yellow") or a string in the 0xRRGGBB[AA]
form (e.g. "0xff00ff"), possibly followed by an alpha specifier.
The default value of <var>shadowcolor</var> is "black".
</p>
</dd>
<dt> ‘<samp>ft_load_flags</samp>’</dt>
<dd><p>The flags to be used for loading the fonts.
</p>
<p>The flags map the corresponding flags supported by libfreetype, and are
a combination of the following values:
</p><dl compact="compact">
<dt> <var>default</var></dt>
<dt> <var>no_scale</var></dt>
<dt> <var>no_hinting</var></dt>
<dt> <var>render</var></dt>
<dt> <var>no_bitmap</var></dt>
<dt> <var>vertical_layout</var></dt>
<dt> <var>force_autohint</var></dt>
<dt> <var>crop_bitmap</var></dt>
<dt> <var>pedantic</var></dt>
<dt> <var>ignore_global_advance_width</var></dt>
<dt> <var>no_recurse</var></dt>
<dt> <var>ignore_transform</var></dt>
<dt> <var>monochrome</var></dt>
<dt> <var>linear_design</var></dt>
<dt> <var>no_autohint</var></dt>
<dt> <var>end table</var></dt>
</dl>
<p>Default value is "render".
</p>
<p>For more information consult the documentation for the FT_LOAD_*
libfreetype flags.
</p>
</dd>
<dt> ‘<samp>tabsize</samp>’</dt>
<dd><p>The size in number of spaces to use for rendering the tab.
Default value is 4.
</p>
</dd>
<dt> ‘<samp>fix_bounds</samp>’</dt>
<dd><p>If true, check and fix text coords to avoid clipping.
</p></dd>
</dl>
<p>For example the command:
</p><table><tr><td> </td><td><pre class="example">drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"
</pre></td></tr></table>
<p>will draw "Test Text" with font FreeSerif, using the default values
for the optional parameters.
</p>
<p>The command:
</p><table><tr><td> </td><td><pre class="example">drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
x=100: y=50: fontsize=24: fontcolor=yellow@0.2: box=1: boxcolor=red@0.2"
</pre></td></tr></table>
<p>will draw ’Test Text’ with font FreeSerif of size 24 at position x=100
and y=50 (counting from the top-left corner of the screen), text is
yellow with a red box around it. Both the text and the box have an
opacity of 20%.
</p>
<p>Note that the double quotes are not necessary if spaces are not used
within the parameter list.
</p>
<p>For more information about libfreetype, check:
<a href="http://www.freetype.org/">http://www.freetype.org/</a>.
</p>
<a name="fade"></a>
<h2 class="section"><a href="avconv.html#toc-fade">24.9 fade</a></h2>
<p>Apply a fade-in/out effect to the input video.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>type</samp>’</dt>
<dd><p>The effect type can be either "in" for a fade-in, or "out" for a fade-out
effect.
</p>
</dd>
<dt> ‘<samp>start_frame</samp>’</dt>
<dd><p>The number of the frame to start applying the fade effect at.
</p>
</dd>
<dt> ‘<samp>nb_frames</samp>’</dt>
<dd><p>The number of frames that the fade effect lasts. At the end of the
fade-in effect, the output video will have the same intensity as the input video.
At the end of the fade-out transition, the output video will be completely black.
</p>
</dd>
</dl>
<p>Some examples:
</p><table><tr><td> </td><td><pre class="example"># Fade in the first 30 frames of video
fade=type=in:nb_frames=30
# Fade out the last 45 frames of a 200-frame video
fade=type=out:start_frame=155:nb_frames=45
# Fade in the first 25 frames and fade out the last 25 frames of a 1000-frame video
fade=type=in:start_frame=0:nb_frames=25, fade=type=out:start_frame=975:nb_frames=25
# Make the first 5 frames black, then fade in from frame 5-24
fade=type=in:start_frame=5:nb_frames=20
</pre></td></tr></table>
<a name="fieldorder"></a>
<h2 class="section"><a href="avconv.html#toc-fieldorder">24.10 fieldorder</a></h2>
<p>Transform the field order of the input video.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>order</samp>’</dt>
<dd><p>The output field order. Valid values are <var>tff</var> for top field first or <var>bff</var>
for bottom field first.
</p></dd>
</dl>
<p>The default value is "tff".
</p>
<p>The transformation is done by shifting the picture content up or down
by one line, and filling the remaining line with appropriate picture content.
This method is consistent with most broadcast field order converters.
</p>
<p>If the input video is not flagged as being interlaced, or it is already
flagged as being of the required output field order, then this filter does
not alter the incoming video.
</p>
<p>It is very useful when converting to or from PAL DV material,
which is bottom field first.
</p>
<p>For example:
</p><table><tr><td> </td><td><pre class="example">./avconv -i in.vob -vf "fieldorder=order=bff" out.dv
</pre></td></tr></table>
<a name="fifo"></a>
<h2 class="section"><a href="avconv.html#toc-fifo">24.11 fifo</a></h2>
<p>Buffer input images and send them when they are requested.
</p>
<p>It is mainly useful when auto-inserted by the libavfilter
framework.
</p>
<p>It does not take parameters.
</p>
<a name="format"></a>
<h2 class="section"><a href="avconv.html#toc-format">24.12 format</a></h2>
<p>Convert the input video to one of the specified pixel formats.
Libavfilter will try to pick one that is suitable as input to
the next filter.
</p>
<p>It accepts the following parameters:
</p><dl compact="compact">
<dt> ‘<samp>pix_fmts</samp>’</dt>
<dd><p>A ’|’-separated list of pixel format names, such as
"pix_fmts=yuv420p|monow|rgb24".
</p>
</dd>
</dl>
<p>Some examples:
</p><table><tr><td> </td><td><pre class="example"># Convert the input video to the "yuv420p" format
format=pix_fmts=yuv420p
# Convert the input video to any of the formats in the list
format=pix_fmts=yuv420p|yuv444p|yuv410p
</pre></td></tr></table>
<p><a name="fps"></a>
</p><a name="fps-1"></a>
<h2 class="section"><a href="avconv.html#toc-fps-1">24.13 fps</a></h2>
<p>Convert the video to specified constant framerate by duplicating or dropping
frames as necessary.
</p>
<p>It accepts the following parameters:
</p><dl compact="compact">
<dt> ‘<samp>fps</samp>’</dt>
<dd><p>The desired output framerate.
</p>
</dd>
<dt> ‘<samp>start_time</samp>’</dt>
<dd><p>Assume the first PTS should be the given value, in seconds. This allows for
padding/trimming at the start of stream. By default, no assumption is made
about the first frame’s expected PTS, so no padding or trimming is done.
For example, this could be set to 0 to pad the beginning with duplicates of
the first frame if a video stream starts after the audio stream or to trim any
frames with a negative PTS.
</p>
</dd>
</dl>
<a name="framepack"></a>
<h2 class="section"><a href="avconv.html#toc-framepack">24.14 framepack</a></h2>
<p>Pack two different video streams into a stereoscopic video, setting proper
metadata on supported codecs. The two views should have the same size and
framerate and processing will stop when the shorter video ends. Please note
that you may conveniently adjust view properties with the <a href="#scale">scale</a> and
<a href="#fps">fps</a> filters.
</p>
<p>It accepts the following parameters:
</p><dl compact="compact">
<dt> ‘<samp>format</samp>’</dt>
<dd><p>The desired packing format. Supported values are:
</p>
<dl compact="compact">
<dt> ‘<samp>sbs</samp>’</dt>
<dd><p>The views are next to each other (default).
</p>
</dd>
<dt> ‘<samp>tab</samp>’</dt>
<dd><p>The views are on top of each other.
</p>
</dd>
<dt> ‘<samp>lines</samp>’</dt>
<dd><p>The views are packed by line.
</p>
</dd>
<dt> ‘<samp>columns</samp>’</dt>
<dd><p>The views are packed by column.
</p>
</dd>
<dt> ‘<samp>frameseq</samp>’</dt>
<dd><p>The views are temporally interleaved.
</p>
</dd>
</dl>
</dd>
</dl>
<p>Some examples:
</p>
<table><tr><td> </td><td><pre class="example"># Convert left and right views into a frame-sequential video
avconv -i LEFT -i RIGHT -filter_complex framepack=frameseq OUTPUT
# Convert views into a side-by-side video with the same output resolution as the input
avconv -i LEFT -i RIGHT -filter_complex [0:v]scale=w=iw/2[left],[1:v]scale=w=iw/2[right],[left][right]framepack=sbs OUTPUT
</pre></td></tr></table>
<p><a name="frei0r"></a>
</p><a name="frei0r-1"></a>
<h2 class="section"><a href="avconv.html#toc-frei0r-1">24.15 frei0r</a></h2>
<p>Apply a frei0r effect to the input video.
</p>
<p>To enable the compilation of this filter, you need to install the frei0r
header and configure Libav with –enable-frei0r.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>filter_name</samp>’</dt>
<dd><p>The name of the frei0r effect to load. If the environment variable
<code>FREI0R_PATH</code> is defined, the frei0r effect is searched for in each of the
directories specified by the colon-separated list in <code>FREIOR_PATH</code>.
Otherwise, the standard frei0r paths are searched, in this order:
‘<tt>HOME/.frei0r-1/lib/</tt>’, ‘<tt>/usr/local/lib/frei0r-1/</tt>’,
‘<tt>/usr/lib/frei0r-1/</tt>’.
</p>
</dd>
<dt> ‘<samp>filter_params</samp>’</dt>
<dd><p>A ’|’-separated list of parameters to pass to the frei0r effect.
</p>
</dd>
</dl>
<p>A frei0r effect parameter can be a boolean (its value is either
"y" or "n"), a double, a color (specified as
<var>R</var>/<var>G</var>/<var>B</var>, where <var>R</var>, <var>G</var>, and <var>B</var> are floating point
numbers between 0.0 and 1.0, inclusive) or by an <code>av_parse_color()</code> color
description), a position (specified as <var>X</var>/<var>Y</var>, where
<var>X</var> and <var>Y</var> are floating point numbers) and/or a string.
</p>
<p>The number and types of parameters depend on the loaded effect. If an
effect parameter is not specified, the default value is set.
</p>
<p>Some examples:
</p><table><tr><td> </td><td><pre class="example"># Apply the distort0r effect, setting the first two double parameters
frei0r=filter_name=distort0r:filter_params=0.5|0.01
# Apply the colordistance effect, taking a color as the first parameter
frei0r=colordistance:0.2/0.3/0.4
frei0r=colordistance:violet
frei0r=colordistance:0x112233
# Apply the perspective effect, specifying the top left and top right
# image positions
frei0r=perspective:0.2/0.2|0.8/0.2
</pre></td></tr></table>
<p>For more information, see
<a href="http://piksel.org/frei0r">http://piksel.org/frei0r</a>
</p>
<a name="gradfun"></a>
<h2 class="section"><a href="avconv.html#toc-gradfun">24.16 gradfun</a></h2>
<p>Fix the banding artifacts that are sometimes introduced into nearly flat
regions by truncation to 8bit colordepth.
Interpolate the gradients that should go where the bands are, and
dither them.
</p>
<p>It is designed for playback only. Do not use it prior to
lossy compression, because compression tends to lose the dither and
bring back the bands.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>strength</samp>’</dt>
<dd><p>The maximum amount by which the filter will change any one pixel. This is also
the threshold for detecting nearly flat regions. Acceptable values range from
.51 to 64; the default value is 1.2. Out-of-range values will be clipped to the
valid range.
</p>
</dd>
<dt> ‘<samp>radius</samp>’</dt>
<dd><p>The neighborhood to fit the gradient to. A larger radius makes for smoother
gradients, but also prevents the filter from modifying the pixels near detailed
regions. Acceptable values are 8-32; the default value is 16. Out-of-range
values will be clipped to the valid range.
</p>
</dd>
</dl>
<table><tr><td> </td><td><pre class="example"># Default parameters
gradfun=strength=1.2:radius=16
# Omitting the radius
gradfun=1.2
</pre></td></tr></table>
<a name="hflip"></a>
<h2 class="section"><a href="avconv.html#toc-hflip">24.17 hflip</a></h2>
<p>Flip the input video horizontally.
</p>
<p>For example, to horizontally flip the input video with <code>avconv</code>:
</p><table><tr><td> </td><td><pre class="example">avconv -i in.avi -vf "hflip" out.avi
</pre></td></tr></table>
<a name="hqdn3d"></a>
<h2 class="section"><a href="avconv.html#toc-hqdn3d">24.18 hqdn3d</a></h2>
<p>This is a high precision/quality 3d denoise filter. It aims to reduce
image noise, producing smooth images and making still images really
still. It should enhance compressibility.
</p>
<p>It accepts the following optional parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>luma_spatial</samp>’</dt>
<dd><p>A non-negative floating point number which specifies spatial luma strength.
It defaults to 4.0.
</p>
</dd>
<dt> ‘<samp>chroma_spatial</samp>’</dt>
<dd><p>A non-negative floating point number which specifies spatial chroma strength.
It defaults to 3.0*<var>luma_spatial</var>/4.0.
</p>
</dd>
<dt> ‘<samp>luma_tmp</samp>’</dt>
<dd><p>A floating point number which specifies luma temporal strength. It defaults to
6.0*<var>luma_spatial</var>/4.0.
</p>
</dd>
<dt> ‘<samp>chroma_tmp</samp>’</dt>
<dd><p>A floating point number which specifies chroma temporal strength. It defaults to
<var>luma_tmp</var>*<var>chroma_spatial</var>/<var>luma_spatial</var>.
</p></dd>
</dl>
<a name="interlace"></a>
<h2 class="section"><a href="avconv.html#toc-interlace">24.19 interlace</a></h2>
<p>Simple interlacing filter from progressive contents. This interleaves upper (or
lower) lines from odd frames with lower (or upper) lines from even frames,
halving the frame rate and preserving image height.
</p>
<table><tr><td> </td><td><pre class="example"> Original Original New Frame
Frame 'j' Frame 'j+1' (tff)
========== =========== ==================
Line 0 --------------------> Frame 'j' Line 0
Line 1 Line 1 ----> Frame 'j+1' Line 1
Line 2 ---------------------> Frame 'j' Line 2
Line 3 Line 3 ----> Frame 'j+1' Line 3
... ... ...
New Frame + 1 will be generated by Frame 'j+2' and Frame 'j+3' and so on
</pre></td></tr></table>
<p>It accepts the following optional parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>scan</samp>’</dt>
<dd><p>This determines whether the interlaced frame is taken from the even
(tff - default) or odd (bff) lines of the progressive frame.
</p>
</dd>
<dt> ‘<samp>lowpass</samp>’</dt>
<dd><p>Enable (default) or disable the vertical lowpass filter to avoid twitter
interlacing and reduce moire patterns.
</p></dd>
</dl>
<a name="lut_002c-lutrgb_002c-lutyuv"></a>
<h2 class="section"><a href="avconv.html#toc-lut_002c-lutrgb_002c-lutyuv">24.20 lut, lutrgb, lutyuv</a></h2>
<p>Compute a look-up table for binding each pixel component input value
to an output value, and apply it to the input video.
</p>
<p><var>lutyuv</var> applies a lookup table to a YUV input video, <var>lutrgb</var>
to an RGB input video.
</p>
<p>These filters accept the following parameters:
</p><dl compact="compact">
<dt> ‘<samp><var>c0</var> (first pixel component)</samp>’</dt>
<dt> ‘<samp><var>c1</var> (second pixel component)</samp>’</dt>
<dt> ‘<samp><var>c2</var> (third pixel component)</samp>’</dt>
<dt> ‘<samp><var>c3</var> (fourth pixel component, corresponds to the alpha component)</samp>’</dt>
<dt> ‘<samp><var>r</var> (red component)</samp>’</dt>
<dt> ‘<samp><var>g</var> (green component)</samp>’</dt>
<dt> ‘<samp><var>b</var> (blue component)</samp>’</dt>
<dt> ‘<samp><var>a</var> (alpha component)</samp>’</dt>
<dt> ‘<samp><var>y</var> (Y/luminance component)</samp>’</dt>
<dt> ‘<samp><var>u</var> (U/Cb component)</samp>’</dt>
<dt> ‘<samp><var>v</var> (V/Cr component)</samp>’</dt>
</dl>
<p>Each of them specifies the expression to use for computing the lookup table for
the corresponding pixel component values.
</p>
<p>The exact component associated to each of the <var>c*</var> options depends on the
format in input.
</p>
<p>The <var>lut</var> filter requires either YUV or RGB pixel formats in input,
<var>lutrgb</var> requires RGB pixel formats in input, and <var>lutyuv</var> requires YUV.
</p>
<p>The expressions can contain the following constants and functions:
</p>
<dl compact="compact">
<dt> ‘<samp>E, PI, PHI</samp>’</dt>
<dd><p>These are approximated values for the mathematical constants e
(Euler’s number), pi (Greek pi), and phi (the golden ratio).
</p>
</dd>
<dt> ‘<samp>w, h</samp>’</dt>
<dd><p>The input width and height.
</p>
</dd>
<dt> ‘<samp>val</samp>’</dt>
<dd><p>The input value for the pixel component.
</p>
</dd>
<dt> ‘<samp>clipval</samp>’</dt>
<dd><p>The input value, clipped to the <var>minval</var>-<var>maxval</var> range.
</p>
</dd>
<dt> ‘<samp>maxval</samp>’</dt>
<dd><p>The maximum value for the pixel component.
</p>
</dd>
<dt> ‘<samp>minval</samp>’</dt>
<dd><p>The minimum value for the pixel component.
</p>
</dd>
<dt> ‘<samp>negval</samp>’</dt>
<dd><p>The negated value for the pixel component value, clipped to the
<var>minval</var>-<var>maxval</var> range; it corresponds to the expression
"maxval-clipval+minval".
</p>
</dd>
<dt> ‘<samp>clip(val)</samp>’</dt>
<dd><p>The computed value in <var>val</var>, clipped to the
<var>minval</var>-<var>maxval</var> range.
</p>
</dd>
<dt> ‘<samp>gammaval(gamma)</samp>’</dt>
<dd><p>The computed gamma correction value of the pixel component value,
clipped to the <var>minval</var>-<var>maxval</var> range. It corresponds to the
expression
"pow((clipval-minval)/(maxval-minval)\,<var>gamma</var>)*(maxval-minval)+minval"
</p>
</dd>
</dl>
<p>All expressions default to "val".
</p>
<p>Some examples:
</p><table><tr><td> </td><td><pre class="example"># Negate input video
lutrgb="r=maxval+minval-val:g=maxval+minval-val:b=maxval+minval-val"
lutyuv="y=maxval+minval-val:u=maxval+minval-val:v=maxval+minval-val"
# The above is the same as
lutrgb="r=negval:g=negval:b=negval"
lutyuv="y=negval:u=negval:v=negval"
# Negate luminance
lutyuv=negval
# Remove chroma components, turning the video into a graytone image
lutyuv="u=128:v=128"
# Apply a luma burning effect
lutyuv="y=2*val"
# Remove green and blue components
lutrgb="g=0:b=0"
# Set a constant alpha channel value on input
format=rgba,lutrgb=a="maxval-minval/2"
# Correct luminance gamma by a factor of 0.5
lutyuv=y=gammaval(0.5)
</pre></td></tr></table>
<a name="negate"></a>
<h2 class="section"><a href="avconv.html#toc-negate">24.21 negate</a></h2>
<p>Negate input video.
</p>
<p>It accepts an integer in input; if non-zero it negates the
alpha component (if available). The default value in input is 0.
</p>
<a name="noformat"></a>
<h2 class="section"><a href="avconv.html#toc-noformat">24.22 noformat</a></h2>
<p>Force libavfilter not to use any of the specified pixel formats for the
input to the next filter.
</p>
<p>It accepts the following parameters:
</p><dl compact="compact">
<dt> ‘<samp>pix_fmts</samp>’</dt>
<dd><p>A ’|’-separated list of pixel format names, such as
apix_fmts=yuv420p|monow|rgb24".
</p>
</dd>
</dl>
<p>Some examples:
</p><table><tr><td> </td><td><pre class="example"># Force libavfilter to use a format different from "yuv420p" for the
# input to the vflip filter
noformat=pix_fmts=yuv420p,vflip
# Convert the input video to any of the formats not contained in the list
noformat=yuv420p|yuv444p|yuv410p
</pre></td></tr></table>
<a name="null-1"></a>
<h2 class="section"><a href="avconv.html#toc-null-1">24.23 null</a></h2>
<p>Pass the video source unchanged to the output.
</p>
<a name="ocv"></a>
<h2 class="section"><a href="avconv.html#toc-ocv">24.24 ocv</a></h2>
<p>Apply a video transform using libopencv.
</p>
<p>To enable this filter, install the libopencv library and headers and
configure Libav with –enable-libopencv.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>filter_name</samp>’</dt>
<dd><p>The name of the libopencv filter to apply.
</p>
</dd>
<dt> ‘<samp>filter_params</samp>’</dt>
<dd><p>The parameters to pass to the libopencv filter. If not specified, the default
values are assumed.
</p>
</dd>
</dl>
<p>Refer to the official libopencv documentation for more precise
information:
<a href="http://opencv.willowgarage.com/documentation/c/image_filtering.html">http://opencv.willowgarage.com/documentation/c/image_filtering.html</a>
</p>
<p>Several libopencv filters are supported; see the following subsections.
</p>
<p><a name="dilate"></a>
</p><a name="dilate-1"></a>
<h3 class="subsection"><a href="avconv.html#toc-dilate-1">24.24.1 dilate</a></h3>
<p>Dilate an image by using a specific structuring element.
It corresponds to the libopencv function <code>cvDilate</code>.
</p>
<p>It accepts the parameters: <var>struct_el</var>|<var>nb_iterations</var>.
</p>
<p><var>struct_el</var> represents a structuring element, and has the syntax:
<var>cols</var>x<var>rows</var>+<var>anchor_x</var>x<var>anchor_y</var>/<var>shape</var>
</p>
<p><var>cols</var> and <var>rows</var> represent the number of columns and rows of
the structuring element, <var>anchor_x</var> and <var>anchor_y</var> the anchor
point, and <var>shape</var> the shape for the structuring element. <var>shape</var>
must be "rect", "cross", "ellipse", or "custom".
</p>
<p>If the value for <var>shape</var> is "custom", it must be followed by a
string of the form "=<var>filename</var>". The file with name
<var>filename</var> is assumed to represent a binary image, with each
printable character corresponding to a bright pixel. When a custom
<var>shape</var> is used, <var>cols</var> and <var>rows</var> are ignored, the number
or columns and rows of the read file are assumed instead.
</p>
<p>The default value for <var>struct_el</var> is "3x3+0x0/rect".
</p>
<p><var>nb_iterations</var> specifies the number of times the transform is
applied to the image, and defaults to 1.
</p>
<p>Some examples:
</p><table><tr><td> </td><td><pre class="example"># Use the default values
ocv=dilate
# Dilate using a structuring element with a 5x5 cross, iterating two times
ocv=filter_name=dilate:filter_params=5x5+2x2/cross|2
# Read the shape from the file diamond.shape, iterating two times.
# The file diamond.shape may contain a pattern of characters like this
# *
# ***
# *****
# ***
# *
# The specified columns and rows are ignored
# but the anchor point coordinates are not
ocv=dilate:0x0+2x2/custom=diamond.shape|2
</pre></td></tr></table>
<a name="erode"></a>
<h3 class="subsection"><a href="avconv.html#toc-erode">24.24.2 erode</a></h3>
<p>Erode an image by using a specific structuring element.
It corresponds to the libopencv function <code>cvErode</code>.
</p>
<p>It accepts the parameters: <var>struct_el</var>:<var>nb_iterations</var>,
with the same syntax and semantics as the <a href="#dilate">dilate</a> filter.
</p>
<a name="smooth"></a>
<h3 class="subsection"><a href="avconv.html#toc-smooth">24.24.3 smooth</a></h3>
<p>Smooth the input video.
</p>
<p>The filter takes the following parameters:
<var>type</var>|<var>param1</var>|<var>param2</var>|<var>param3</var>|<var>param4</var>.
</p>
<p><var>type</var> is the type of smooth filter to apply, and must be one of
the following values: "blur", "blur_no_scale", "median", "gaussian",
or "bilateral". The default value is "gaussian".
</p>
<p>The meaning of <var>param1</var>, <var>param2</var>, <var>param3</var>, and <var>param4</var>
depend on the smooth type. <var>param1</var> and
<var>param2</var> accept integer positive values or 0. <var>param3</var> and
<var>param4</var> accept floating point values.
</p>
<p>The default value for <var>param1</var> is 3. The default value for the
other parameters is 0.
</p>
<p>These parameters correspond to the parameters assigned to the
libopencv function <code>cvSmooth</code>.
</p>
<p><a name="overlay"></a>
</p><a name="overlay-1"></a>
<h2 class="section"><a href="avconv.html#toc-overlay-1">24.25 overlay</a></h2>
<p>Overlay one video on top of another.
</p>
<p>It takes two inputs and has one output. The first input is the "main"
video on which the second input is overlayed.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>x</samp>’</dt>
<dd><p>The horizontal position of the left edge of the overlaid video on the main video.
</p>
</dd>
<dt> ‘<samp>y</samp>’</dt>
<dd><p>The vertical position of the top edge of the overlaid video on the main video.
</p>
</dd>
</dl>
<p>The parameters are expressions containing the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>main_w, main_h</samp>’</dt>
<dd><p>The main input width and height.
</p>
</dd>
<dt> ‘<samp>W, H</samp>’</dt>
<dd><p>These are the same as <var>main_w</var> and <var>main_h</var>.
</p>
</dd>
<dt> ‘<samp>overlay_w, overlay_h</samp>’</dt>
<dd><p>The overlay input width and height.
</p>
</dd>
<dt> ‘<samp>w, h</samp>’</dt>
<dd><p>These are the same as <var>overlay_w</var> and <var>overlay_h</var>.
</p>
</dd>
<dt> ‘<samp>eof_action</samp>’</dt>
<dd><p>The action to take when EOF is encountered on the secondary input; it accepts
one of the following values:
</p>
<dl compact="compact">
<dt> ‘<samp>repeat</samp>’</dt>
<dd><p>Repeat the last frame (the default).
</p></dd>
<dt> ‘<samp>endall</samp>’</dt>
<dd><p>End both streams.
</p></dd>
<dt> ‘<samp>pass</samp>’</dt>
<dd><p>Pass the main input through.
</p></dd>
</dl>
</dd>
</dl>
<p>Be aware that frames are taken from each input video in timestamp
order, hence, if their initial timestamps differ, it is a a good idea
to pass the two inputs through a <var>setpts=PTS-STARTPTS</var> filter to
have them begin in the same zero timestamp, as the example for
the <var>movie</var> filter does.
</p>
<p>Some examples:
</p><table><tr><td> </td><td><pre class="example"># Draw the overlay at 10 pixels from the bottom right
# corner of the main video
overlay=x=main_w-overlay_w-10:y=main_h-overlay_h-10
# Insert a transparent PNG logo in the bottom left corner of the input
avconv -i input -i logo -filter_complex 'overlay=x=10:y=main_h-overlay_h-10' output
# Insert 2 different transparent PNG logos (second logo on bottom
# right corner)
avconv -i input -i logo1 -i logo2 -filter_complex
'overlay=x=10:y=H-h-10,overlay=x=W-w-10:y=H-h-10' output
# Add a transparent color layer on top of the main video;
# WxH specifies the size of the main input to the overlay filter
color=red.3:WxH [over]; [in][over] overlay [out]
# Mask 10-20 seconds of a video by applying the delogo filter to a section
avconv -i test.avi -codec:v:0 wmv2 -ar 11025 -b:v 9000k
-vf '[in]split[split_main][split_delogo];[split_delogo]trim=start=360:end=371,delogo=0:0:640:480[delogoed];[split_main][delogoed]overlay=eof_action=pass[out]'
masked.avi
</pre></td></tr></table>
<p>You can chain together more overlays but the efficiency of such
approach is yet to be tested.
</p>
<a name="pad"></a>
<h2 class="section"><a href="avconv.html#toc-pad">24.26 pad</a></h2>
<p>Add paddings to the input image, and place the original input at the
provided <var>x</var>, <var>y</var> coordinates.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>width, height</samp>’</dt>
<dd>
<p>Specify the size of the output image with the paddings added. If the
value for <var>width</var> or <var>height</var> is 0, the corresponding input size
is used for the output.
</p>
<p>The <var>width</var> expression can reference the value set by the
<var>height</var> expression, and vice versa.
</p>
<p>The default value of <var>width</var> and <var>height</var> is 0.
</p>
</dd>
<dt> ‘<samp>x, y</samp>’</dt>
<dd>
<p>Specify the offsets to place the input image at within the padded area,
with respect to the top/left border of the output image.
</p>
<p>The <var>x</var> expression can reference the value set by the <var>y</var>
expression, and vice versa.
</p>
<p>The default value of <var>x</var> and <var>y</var> is 0.
</p>
</dd>
<dt> ‘<samp>color</samp>’</dt>
<dd>
<p>Specify the color of the padded area. It can be the name of a color
(case insensitive match) or an 0xRRGGBB[AA] sequence.
</p>
<p>The default value of <var>color</var> is "black".
</p>
</dd>
</dl>
<p>The parameters <var>width</var>, <var>height</var>, <var>x</var>, and <var>y</var> are
expressions containing the following constants:
</p>
<dl compact="compact">
<dt> ‘<samp>E, PI, PHI</samp>’</dt>
<dd><p>These are approximated values for the mathematical constants e
(Euler’s number), pi (Greek pi), and phi (the golden ratio).
</p>
</dd>
<dt> ‘<samp>in_w, in_h</samp>’</dt>
<dd><p>The input video width and height.
</p>
</dd>
<dt> ‘<samp>iw, ih</samp>’</dt>
<dd><p>These are the same as <var>in_w</var> and <var>in_h</var>.
</p>
</dd>
<dt> ‘<samp>out_w, out_h</samp>’</dt>
<dd><p>The output width and height (the size of the padded area), as
specified by the <var>width</var> and <var>height</var> expressions.
</p>
</dd>
<dt> ‘<samp>ow, oh</samp>’</dt>
<dd><p>These are the same as <var>out_w</var> and <var>out_h</var>.
</p>
</dd>
<dt> ‘<samp>x, y</samp>’</dt>
<dd><p>The x and y offsets as specified by the <var>x</var> and <var>y</var>
expressions, or NAN if not yet specified.
</p>
</dd>
<dt> ‘<samp>a</samp>’</dt>
<dd><p>The input display aspect ratio, same as <var>iw</var> / <var>ih</var>.
</p>
</dd>
<dt> ‘<samp>hsub, vsub</samp>’</dt>
<dd><p>The horizontal and vertical chroma subsample values. For example for the
pixel format "yuv422p" <var>hsub</var> is 2 and <var>vsub</var> is 1.
</p></dd>
</dl>
<p>Some examples:
</p>
<table><tr><td> </td><td><pre class="example"># Add paddings with the color "violet" to the input video. The output video
# size is 640x480, and the top-left corner of the input video is placed at
# column 0, row 40
pad=width=640:height=480:x=0:y=40:color=violet
# Pad the input to get an output with dimensions increased by 3/2,
# and put the input video at the center of the padded area
pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"
# Pad the input to get a squared output with size equal to the maximum
# value between the input width and height, and put the input video at
# the center of the padded area
pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"
# Pad the input to get a final w/h ratio of 16:9
pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"
# Double the output size and put the input video in the bottom-right
# corner of the output padded area
pad="2*iw:2*ih:ow-iw:oh-ih"
</pre></td></tr></table>
<a name="pixdesctest"></a>
<h2 class="section"><a href="avconv.html#toc-pixdesctest">24.27 pixdesctest</a></h2>
<p>Pixel format descriptor test filter, mainly useful for internal
testing. The output video should be equal to the input video.
</p>
<p>For example:
</p><table><tr><td> </td><td><pre class="example">format=monow, pixdesctest
</pre></td></tr></table>
<p>can be used to test the monowhite pixel format descriptor definition.
</p>
<p><a name="scale"></a>
</p><a name="scale-1"></a>
<h2 class="section"><a href="avconv.html#toc-scale-1">24.28 scale</a></h2>
<p>Scale the input video and/or convert the image format.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>w</samp>’</dt>
<dd><p>The output video width.
</p>
</dd>
<dt> ‘<samp>h</samp>’</dt>
<dd><p>The output video height.
</p>
</dd>
</dl>
<p>The parameters <var>w</var> and <var>h</var> are expressions containing
the following constants:
</p>
<dl compact="compact">
<dt> ‘<samp>E, PI, PHI</samp>’</dt>
<dd><p>These are approximated values for the mathematical constants e
(Euler’s number), pi (Greek pi), and phi (the golden ratio).
</p>
</dd>
<dt> ‘<samp>in_w, in_h</samp>’</dt>
<dd><p>The input width and height.
</p>
</dd>
<dt> ‘<samp>iw, ih</samp>’</dt>
<dd><p>These are the same as <var>in_w</var> and <var>in_h</var>.
</p>
</dd>
<dt> ‘<samp>out_w, out_h</samp>’</dt>
<dd><p>The output (cropped) width and height.
</p>
</dd>
<dt> ‘<samp>ow, oh</samp>’</dt>
<dd><p>These are the same as <var>out_w</var> and <var>out_h</var>.
</p>
</dd>
<dt> ‘<samp>a</samp>’</dt>
<dd><p>This is the same as <var>iw</var> / <var>ih</var>.
</p>
</dd>
<dt> ‘<samp>sar</samp>’</dt>
<dd><p>input sample aspect ratio
</p>
</dd>
<dt> ‘<samp>dar</samp>’</dt>
<dd><p>The input display aspect ratio; it is the same as
(<var>iw</var> / <var>ih</var>) * <var>sar</var>.
</p>
</dd>
<dt> ‘<samp>hsub, vsub</samp>’</dt>
<dd><p>The horizontal and vertical chroma subsample values. For example, for the
pixel format "yuv422p" <var>hsub</var> is 2 and <var>vsub</var> is 1.
</p></dd>
</dl>
<p>If the input image format is different from the format requested by
the next filter, the scale filter will convert the input to the
requested format.
</p>
<p>If the value for <var>w</var> or <var>h</var> is 0, the respective input
size is used for the output.
</p>
<p>If the value for <var>w</var> or <var>h</var> is -1, the scale filter will use, for the
respective output size, a value that maintains the aspect ratio of the input
image.
</p>
<p>The default value of <var>w</var> and <var>h</var> is 0.
</p>
<p>Some examples:
</p><table><tr><td> </td><td><pre class="example"># Scale the input video to a size of 200x100
scale=w=200:h=100
# Scale the input to 2x
scale=w=2*iw:h=2*ih
# The above is the same as
scale=2*in_w:2*in_h
# Scale the input to half the original size
scale=w=iw/2:h=ih/2
# Increase the width, and set the height to the same size
scale=3/2*iw:ow
# Seek Greek harmony
scale=iw:1/PHI*iw
scale=ih*PHI:ih
# Increase the height, and set the width to 3/2 of the height
scale=w=3/2*oh:h=3/5*ih
# Increase the size, making the size a multiple of the chroma
scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"
# Increase the width to a maximum of 500 pixels,
# keeping the same aspect ratio as the input
scale=w='min(500\, iw*3/2):h=-1'
</pre></td></tr></table>
<a name="select"></a>
<h2 class="section"><a href="avconv.html#toc-select">24.29 select</a></h2>
<p>Select frames to pass in output.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>expr</samp>’</dt>
<dd><p>An expression, which is evaluated for each input frame. If the expression is
evaluated to a non-zero value, the frame is selected and passed to the output,
otherwise it is discarded.
</p>
</dd>
</dl>
<p>The expression can contain the following constants:
</p>
<dl compact="compact">
<dt> ‘<samp>E, PI, PHI</samp>’</dt>
<dd><p>These are approximated values for the mathematical constants e
(Euler’s number), pi (Greek pi), and phi (the golden ratio).
</p>
</dd>
<dt> ‘<samp>n</samp>’</dt>
<dd><p>The (sequential) number of the filtered frame, starting from 0.
</p>
</dd>
<dt> ‘<samp>selected_n</samp>’</dt>
<dd><p>The (sequential) number of the selected frame, starting from 0.
</p>
</dd>
<dt> ‘<samp>prev_selected_n</samp>’</dt>
<dd><p>The sequential number of the last selected frame. It’s NAN if undefined.
</p>
</dd>
<dt> ‘<samp>TB</samp>’</dt>
<dd><p>The timebase of the input timestamps.
</p>
</dd>
<dt> ‘<samp>pts</samp>’</dt>
<dd><p>The PTS (Presentation TimeStamp) of the filtered video frame,
expressed in <var>TB</var> units. It’s NAN if undefined.
</p>
</dd>
<dt> ‘<samp>t</samp>’</dt>
<dd><p>The PTS of the filtered video frame,
expressed in seconds. It’s NAN if undefined.
</p>
</dd>
<dt> ‘<samp>prev_pts</samp>’</dt>
<dd><p>The PTS of the previously filtered video frame. It’s NAN if undefined.
</p>
</dd>
<dt> ‘<samp>prev_selected_pts</samp>’</dt>
<dd><p>The PTS of the last previously filtered video frame. It’s NAN if undefined.
</p>
</dd>
<dt> ‘<samp>prev_selected_t</samp>’</dt>
<dd><p>The PTS of the last previously selected video frame. It’s NAN if undefined.
</p>
</dd>
<dt> ‘<samp>start_pts</samp>’</dt>
<dd><p>The PTS of the first video frame in the video. It’s NAN if undefined.
</p>
</dd>
<dt> ‘<samp>start_t</samp>’</dt>
<dd><p>The time of the first video frame in the video. It’s NAN if undefined.
</p>
</dd>
<dt> ‘<samp>pict_type</samp>’</dt>
<dd><p>The type of the filtered frame. It can assume one of the following
values:
</p><dl compact="compact">
<dt> ‘<samp>I</samp>’</dt>
<dt> ‘<samp>P</samp>’</dt>
<dt> ‘<samp>B</samp>’</dt>
<dt> ‘<samp>S</samp>’</dt>
<dt> ‘<samp>SI</samp>’</dt>
<dt> ‘<samp>SP</samp>’</dt>
<dt> ‘<samp>BI</samp>’</dt>
</dl>
</dd>
<dt> ‘<samp>interlace_type</samp>’</dt>
<dd><p>The frame interlace type. It can assume one of the following values:
</p><dl compact="compact">
<dt> ‘<samp>PROGRESSIVE</samp>’</dt>
<dd><p>The frame is progressive (not interlaced).
</p></dd>
<dt> ‘<samp>TOPFIRST</samp>’</dt>
<dd><p>The frame is top-field-first.
</p></dd>
<dt> ‘<samp>BOTTOMFIRST</samp>’</dt>
<dd><p>The frame is bottom-field-first.
</p></dd>
</dl>
</dd>
<dt> ‘<samp>key</samp>’</dt>
<dd><p>This is 1 if the filtered frame is a key-frame, 0 otherwise.
</p>
</dd>
</dl>
<p>The default value of the select expression is "1".
</p>
<p>Some examples:
</p>
<table><tr><td> </td><td><pre class="example"># Select all the frames in input
select
# The above is the same as
select=expr=1
# Skip all frames
select=expr=0
# Select only I-frames
select='expr=eq(pict_type\,I)'
# Select one frame per 100
select='not(mod(n\,100))'
# Select only frames contained in the 10-20 time interval
select='gte(t\,10)*lte(t\,20)'
# Select only I frames contained in the 10-20 time interval
select='gte(t\,10)*lte(t\,20)*eq(pict_type\,I)'
# Select frames with a minimum distance of 10 seconds
select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'
</pre></td></tr></table>
<p><a name="setdar"></a>
</p><a name="setdar-1"></a>
<h2 class="section"><a href="avconv.html#toc-setdar-1">24.30 setdar</a></h2>
<p>Set the Display Aspect Ratio for the filter output video.
</p>
<p>This is done by changing the specified Sample (aka Pixel) Aspect
Ratio, according to the following equation:
<em>DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR</em>
</p>
<p>Keep in mind that this filter does not modify the pixel dimensions of
the video frame. Also, the display aspect ratio set by this filter may
be changed by later filters in the filterchain, e.g. in case of
scaling or if another "setdar" or a "setsar" filter is applied.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>dar</samp>’</dt>
<dd><p>The output display aspect ratio.
</p>
</dd>
</dl>
<p>The parameter <var>dar</var> is an expression containing
the following constants:
</p>
<dl compact="compact">
<dt> ‘<samp>E, PI, PHI</samp>’</dt>
<dd><p>These are approximated values for the mathematical constants e
(Euler’s number), pi (Greek pi), and phi (the golden ratio).
</p>
</dd>
<dt> ‘<samp>w, h</samp>’</dt>
<dd><p>The input width and height.
</p>
</dd>
<dt> ‘<samp>a</samp>’</dt>
<dd><p>This is the same as <var>w</var> / <var>h</var>.
</p>
</dd>
<dt> ‘<samp>sar</samp>’</dt>
<dd><p>The input sample aspect ratio.
</p>
</dd>
<dt> ‘<samp>dar</samp>’</dt>
<dd><p>The input display aspect ratio. It is the same as
(<var>w</var> / <var>h</var>) * <var>sar</var>.
</p>
</dd>
<dt> ‘<samp>hsub, vsub</samp>’</dt>
<dd><p>The horizontal and vertical chroma subsample values. For example, for the
pixel format "yuv422p" <var>hsub</var> is 2 and <var>vsub</var> is 1.
</p></dd>
</dl>
<p>To change the display aspect ratio to 16:9, specify:
</p><table><tr><td> </td><td><pre class="example">setdar=dar=16/9
# The above is equivalent to
setdar=dar=1.77777
</pre></td></tr></table>
<p>Also see the the <a href="#setsar">setsar</a> filter documentation.
</p>
<a name="setpts"></a>
<h2 class="section"><a href="avconv.html#toc-setpts">24.31 setpts</a></h2>
<p>Change the PTS (presentation timestamp) of the input video frames.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>expr</samp>’</dt>
<dd><p>The expression which is evaluated for each frame to construct its timestamp.
</p>
</dd>
</dl>
<p>The expression is evaluated through the eval API and can contain the following
constants:
</p>
<dl compact="compact">
<dt> ‘<samp>PTS</samp>’</dt>
<dd><p>The presentation timestamp in input.
</p>
</dd>
<dt> ‘<samp>E, PI, PHI</samp>’</dt>
<dd><p>These are approximated values for the mathematical constants e
(Euler’s number), pi (Greek pi), and phi (the golden ratio).
</p>
</dd>
<dt> ‘<samp>N</samp>’</dt>
<dd><p>The count of the input frame, starting from 0.
</p>
</dd>
<dt> ‘<samp>STARTPTS</samp>’</dt>
<dd><p>The PTS of the first video frame.
</p>
</dd>
<dt> ‘<samp>INTERLACED</samp>’</dt>
<dd><p>State whether the current frame is interlaced.
</p>
</dd>
<dt> ‘<samp>PREV_INPTS</samp>’</dt>
<dd><p>The previous input PTS.
</p>
</dd>
<dt> ‘<samp>PREV_OUTPTS</samp>’</dt>
<dd><p>The previous output PTS.
</p>
</dd>
<dt> ‘<samp>RTCTIME</samp>’</dt>
<dd><p>The wallclock (RTC) time in microseconds.
</p>
</dd>
<dt> ‘<samp>RTCSTART</samp>’</dt>
<dd><p>The wallclock (RTC) time at the start of the movie in microseconds.
</p>
</dd>
<dt> ‘<samp>TB</samp>’</dt>
<dd><p>The timebase of the input timestamps.
</p>
</dd>
</dl>
<p>Some examples:
</p>
<table><tr><td> </td><td><pre class="example"># Start counting the PTS from zero
setpts=expr=PTS-STARTPTS
# Fast motion
setpts=expr=0.5*PTS
# Slow motion
setpts=2.0*PTS
# Fixed rate 25 fps
setpts=N/(25*TB)
# Fixed rate 25 fps with some jitter
setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
# Generate timestamps from a "live source" and rebase onto the current timebase
setpts='(RTCTIME - RTCSTART) / (TB * 1000000)"
</pre></td></tr></table>
<p><a name="setsar"></a>
</p><a name="setsar-1"></a>
<h2 class="section"><a href="avconv.html#toc-setsar-1">24.32 setsar</a></h2>
<p>Set the Sample (aka Pixel) Aspect Ratio for the filter output video.
</p>
<p>Note that as a consequence of the application of this filter, the
output display aspect ratio will change according to the following
equation:
<em>DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR</em>
</p>
<p>Keep in mind that the sample aspect ratio set by this filter may be
changed by later filters in the filterchain, e.g. if another "setsar"
or a "setdar" filter is applied.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>sar</samp>’</dt>
<dd><p>The output sample aspect ratio.
</p>
</dd>
</dl>
<p>The parameter <var>sar</var> is an expression containing
the following constants:
</p>
<dl compact="compact">
<dt> ‘<samp>E, PI, PHI</samp>’</dt>
<dd><p>These are approximated values for the mathematical constants e
(Euler’s number), pi (Greek pi), and phi (the golden ratio).
</p>
</dd>
<dt> ‘<samp>w, h</samp>’</dt>
<dd><p>The input width and height.
</p>
</dd>
<dt> ‘<samp>a</samp>’</dt>
<dd><p>These are the same as <var>w</var> / <var>h</var>.
</p>
</dd>
<dt> ‘<samp>sar</samp>’</dt>
<dd><p>The input sample aspect ratio.
</p>
</dd>
<dt> ‘<samp>dar</samp>’</dt>
<dd><p>The input display aspect ratio. It is the same as
(<var>w</var> / <var>h</var>) * <var>sar</var>.
</p>
</dd>
<dt> ‘<samp>hsub, vsub</samp>’</dt>
<dd><p>Horizontal and vertical chroma subsample values. For example, for the
pixel format "yuv422p" <var>hsub</var> is 2 and <var>vsub</var> is 1.
</p></dd>
</dl>
<p>To change the sample aspect ratio to 10:11, specify:
</p><table><tr><td> </td><td><pre class="example">setsar=sar=10/11
</pre></td></tr></table>
<a name="settb"></a>
<h2 class="section"><a href="avconv.html#toc-settb">24.33 settb</a></h2>
<p>Set the timebase to use for the output frames timestamps.
It is mainly useful for testing timebase configuration.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>expr</samp>’</dt>
<dd><p>The expression which is evaluated into the output timebase.
</p>
</dd>
</dl>
<p>The expression can contain the constants "PI", "E", "PHI", "AVTB" (the
default timebase), and "intb" (the input timebase).
</p>
<p>The default value for the input is "intb".
</p>
<p>Some examples:
</p>
<table><tr><td> </td><td><pre class="example"># Set the timebase to 1/25
settb=expr=1/25
# Set the timebase to 1/10
settb=expr=0.1
# Set the timebase to 1001/1000
settb=1+0.001
#Set the timebase to 2*intb
settb=2*intb
#Set the default timebase value
settb=AVTB
</pre></td></tr></table>
<a name="showinfo"></a>
<h2 class="section"><a href="avconv.html#toc-showinfo">24.34 showinfo</a></h2>
<p>Show a line containing various information for each input video frame.
The input video is not modified.
</p>
<p>The shown line contains a sequence of key/value pairs of the form
<var>key</var>:<var>value</var>.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>n</samp>’</dt>
<dd><p>The (sequential) number of the input frame, starting from 0.
</p>
</dd>
<dt> ‘<samp>pts</samp>’</dt>
<dd><p>The Presentation TimeStamp of the input frame, expressed as a number of
time base units. The time base unit depends on the filter input pad.
</p>
</dd>
<dt> ‘<samp>pts_time</samp>’</dt>
<dd><p>The Presentation TimeStamp of the input frame, expressed as a number of
seconds.
</p>
</dd>
<dt> ‘<samp>pos</samp>’</dt>
<dd><p>The position of the frame in the input stream, or -1 if this information is
unavailable and/or meaningless (for example in case of synthetic video).
</p>
</dd>
<dt> ‘<samp>fmt</samp>’</dt>
<dd><p>The pixel format name.
</p>
</dd>
<dt> ‘<samp>sar</samp>’</dt>
<dd><p>The sample aspect ratio of the input frame, expressed in the form
<var>num</var>/<var>den</var>.
</p>
</dd>
<dt> ‘<samp>s</samp>’</dt>
<dd><p>The size of the input frame, expressed in the form
<var>width</var>x<var>height</var>.
</p>
</dd>
<dt> ‘<samp>i</samp>’</dt>
<dd><p>The type of interlaced mode ("P" for "progressive", "T" for top field first, "B"
for bottom field first).
</p>
</dd>
<dt> ‘<samp>iskey</samp>’</dt>
<dd><p>This is 1 if the frame is a key frame, 0 otherwise.
</p>
</dd>
<dt> ‘<samp>type</samp>’</dt>
<dd><p>The picture type of the input frame ("I" for an I-frame, "P" for a
P-frame, "B" for a B-frame, or "?" for an unknown type).
Also refer to the documentation of the <code>AVPictureType</code> enum and of
the <code>av_get_picture_type_char</code> function defined in
‘<tt>libavutil/avutil.h</tt>’.
</p>
</dd>
<dt> ‘<samp>checksum</samp>’</dt>
<dd><p>The Adler-32 checksum of all the planes of the input frame.
</p>
</dd>
<dt> ‘<samp>plane_checksum</samp>’</dt>
<dd><p>The Adler-32 checksum of each plane of the input frame, expressed in the form
"[<var>c0</var> <var>c1</var> <var>c2</var> <var>c3</var>]".
</p></dd>
</dl>
<a name="shuffleplanes"></a>
<h2 class="section"><a href="avconv.html#toc-shuffleplanes">24.35 shuffleplanes</a></h2>
<p>Reorder and/or duplicate video planes.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>map0</samp>’</dt>
<dd><p>The index of the input plane to be used as the first output plane.
</p>
</dd>
<dt> ‘<samp>map1</samp>’</dt>
<dd><p>The index of the input plane to be used as the second output plane.
</p>
</dd>
<dt> ‘<samp>map2</samp>’</dt>
<dd><p>The index of the input plane to be used as the third output plane.
</p>
</dd>
<dt> ‘<samp>map3</samp>’</dt>
<dd><p>The index of the input plane to be used as the fourth output plane.
</p>
</dd>
</dl>
<p>The first plane has the index 0. The default is to keep the input unchanged.
</p>
<p>Swap the second and third planes of the input:
</p><table><tr><td> </td><td><pre class="example">avconv -i INPUT -vf shuffleplanes=0:2:1:3 OUTPUT
</pre></td></tr></table>
<a name="split"></a>
<h2 class="section"><a href="avconv.html#toc-split">24.36 split</a></h2>
<p>Split input video into several identical outputs.
</p>
<p>It accepts a single parameter, which specifies the number of outputs. If
unspecified, it defaults to 2.
</p>
<p>Create 5 copies of the input video:
</p><table><tr><td> </td><td><pre class="example">avconv -i INPUT -filter_complex split=5 OUTPUT
</pre></td></tr></table>
<a name="transpose"></a>
<h2 class="section"><a href="avconv.html#toc-transpose">24.37 transpose</a></h2>
<p>Transpose rows with columns in the input video and optionally flip it.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>dir</samp>’</dt>
<dd><p>The direction of the transpose.
</p>
</dd>
</dl>
<p>The direction can assume the following values:
</p>
<dl compact="compact">
<dt> ‘<samp>cclock_flip</samp>’</dt>
<dd><p>Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
</p><table><tr><td> </td><td><pre class="example">L.R L.l
. . -> . .
l.r R.r
</pre></td></tr></table>
</dd>
<dt> ‘<samp>clock</samp>’</dt>
<dd><p>Rotate by 90 degrees clockwise, that is:
</p><table><tr><td> </td><td><pre class="example">L.R l.L
. . -> . .
l.r r.R
</pre></td></tr></table>
</dd>
<dt> ‘<samp>cclock</samp>’</dt>
<dd><p>Rotate by 90 degrees counterclockwise, that is:
</p><table><tr><td> </td><td><pre class="example">L.R R.r
. . -> . .
l.r L.l
</pre></td></tr></table>
</dd>
<dt> ‘<samp>clock_flip</samp>’</dt>
<dd><p>Rotate by 90 degrees clockwise and vertically flip, that is:
</p><table><tr><td> </td><td><pre class="example">L.R r.R
. . -> . .
l.r l.L
</pre></td></tr></table>
</dd>
</dl>
<a name="trim"></a>
<h2 class="section"><a href="avconv.html#toc-trim">24.38 trim</a></h2>
<p>Trim the input so that the output contains one continuous subpart of the input.
</p>
<p>It accepts the following parameters:
</p><dl compact="compact">
<dt> ‘<samp>start</samp>’</dt>
<dd><p>The timestamp (in seconds) of the start of the kept section. The frame with the
timestamp <var>start</var> will be the first frame in the output.
</p>
</dd>
<dt> ‘<samp>end</samp>’</dt>
<dd><p>The timestamp (in seconds) of the first frame that will be dropped. The frame
immediately preceding the one with the timestamp <var>end</var> will be the last
frame in the output.
</p>
</dd>
<dt> ‘<samp>start_pts</samp>’</dt>
<dd><p>This is the same as <var>start</var>, except this option sets the start timestamp
in timebase units instead of seconds.
</p>
</dd>
<dt> ‘<samp>end_pts</samp>’</dt>
<dd><p>This is the same as <var>end</var>, except this option sets the end timestamp
in timebase units instead of seconds.
</p>
</dd>
<dt> ‘<samp>duration</samp>’</dt>
<dd><p>The maximum duration of the output in seconds.
</p>
</dd>
<dt> ‘<samp>start_frame</samp>’</dt>
<dd><p>The number of the first frame that should be passed to the output.
</p>
</dd>
<dt> ‘<samp>end_frame</samp>’</dt>
<dd><p>The number of the first frame that should be dropped.
</p></dd>
</dl>
<p>Note that the first two sets of the start/end options and the ‘<samp>duration</samp>’
option look at the frame timestamp, while the _frame variants simply count the
frames that pass through the filter. Also note that this filter does not modify
the timestamps. If you wish for the output timestamps to start at zero, insert a
setpts filter after the trim filter.
</p>
<p>If multiple start or end options are set, this filter tries to be greedy and
keep all the frames that match at least one of the specified constraints. To keep
only the part that matches all the constraints at once, chain multiple trim
filters.
</p>
<p>The defaults are such that all the input is kept. So it is possible to set e.g.
just the end values to keep everything before the specified time.
</p>
<p>Examples:
</p><ul>
<li>
Drop everything except the second minute of input:
<table><tr><td> </td><td><pre class="example">avconv -i INPUT -vf trim=60:120
</pre></td></tr></table>
</li><li>
Keep only the first second:
<table><tr><td> </td><td><pre class="example">avconv -i INPUT -vf trim=duration=1
</pre></td></tr></table>
</li></ul>
<a name="unsharp"></a>
<h2 class="section"><a href="avconv.html#toc-unsharp">24.39 unsharp</a></h2>
<p>Sharpen or blur the input video.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>luma_msize_x</samp>’</dt>
<dd><p>Set the luma matrix horizontal size. It must be an integer between 3
and 13. The default value is 5.
</p>
</dd>
<dt> ‘<samp>luma_msize_y</samp>’</dt>
<dd><p>Set the luma matrix vertical size. It must be an integer between 3
and 13. The default value is 5.
</p>
</dd>
<dt> ‘<samp>luma_amount</samp>’</dt>
<dd><p>Set the luma effect strength. It must be a floating point number between -2.0
and 5.0. The default value is 1.0.
</p>
</dd>
<dt> ‘<samp>chroma_msize_x</samp>’</dt>
<dd><p>Set the chroma matrix horizontal size. It must be an integer between 3
and 13. The default value is 5.
</p>
</dd>
<dt> ‘<samp>chroma_msize_y</samp>’</dt>
<dd><p>Set the chroma matrix vertical size. It must be an integer between 3
and 13. The default value is 5.
</p>
</dd>
<dt> ‘<samp>chroma_amount</samp>’</dt>
<dd><p>Set the chroma effect strength. It must be a floating point number between -2.0
and 5.0. The default value is 0.0.
</p>
</dd>
</dl>
<p>Negative values for the amount will blur the input video, while positive
values will sharpen. All parameters are optional and default to the
equivalent of the string ’5:5:1.0:5:5:0.0’.
</p>
<table><tr><td> </td><td><pre class="example"># Strong luma sharpen effect parameters
unsharp=luma_msize_x=7:luma_msize_y=7:luma_amount=2.5
# A strong blur of both luma and chroma parameters
unsharp=7:7:-2:7:7:-2
# Use the default values with <code>avconv</code>
./avconv -i in.avi -vf "unsharp" out.mp4
</pre></td></tr></table>
<a name="vflip"></a>
<h2 class="section"><a href="avconv.html#toc-vflip">24.40 vflip</a></h2>
<p>Flip the input video vertically.
</p>
<table><tr><td> </td><td><pre class="example">./avconv -i in.avi -vf "vflip" out.avi
</pre></td></tr></table>
<a name="yadif"></a>
<h2 class="section"><a href="avconv.html#toc-yadif">24.41 yadif</a></h2>
<p>Deinterlace the input video ("yadif" means "yet another deinterlacing
filter").
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>mode</samp>’</dt>
<dd><p>The interlacing mode to adopt. It accepts one of the following values:
</p>
<dl compact="compact">
<dt> ‘<samp>0</samp>’</dt>
<dd><p>Output one frame for each frame.
</p></dd>
<dt> ‘<samp>1</samp>’</dt>
<dd><p>Output one frame for each field.
</p></dd>
<dt> ‘<samp>2</samp>’</dt>
<dd><p>Like 0, but it skips the spatial interlacing check.
</p></dd>
<dt> ‘<samp>3</samp>’</dt>
<dd><p>Like 1, but it skips the spatial interlacing check.
</p></dd>
</dl>
<p>The default value is 0.
</p>
</dd>
<dt> ‘<samp>parity</samp>’</dt>
<dd><p>The picture field parity assumed for the input interlaced video. It accepts one
of the following values:
</p>
<dl compact="compact">
<dt> ‘<samp>0</samp>’</dt>
<dd><p>Assume the top field is first.
</p></dd>
<dt> ‘<samp>1</samp>’</dt>
<dd><p>Assume the bottom field is first.
</p></dd>
<dt> ‘<samp>-1</samp>’</dt>
<dd><p>Enable automatic detection of field parity.
</p></dd>
</dl>
<p>The default value is -1.
If the interlacing is unknown or the decoder does not export this information,
top field first will be assumed.
</p>
</dd>
<dt> ‘<samp>auto</samp>’</dt>
<dd><p>Whether the deinterlacer should trust the interlaced flag and only deinterlace
frames marked as interlaced.
</p>
<dl compact="compact">
<dt> ‘<samp>0</samp>’</dt>
<dd><p>Deinterlace all frames.
</p></dd>
<dt> ‘<samp>1</samp>’</dt>
<dd><p>Only deinterlace frames marked as interlaced.
</p></dd>
</dl>
<p>The default value is 0.
</p>
</dd>
</dl>
<a name="Video-Sources"></a>
<h1 class="chapter"><a href="avconv.html#toc-Video-Sources">25. Video Sources</a></h1>
<p>Below is a description of the currently available video sources.
</p>
<a name="buffer"></a>
<h2 class="section"><a href="avconv.html#toc-buffer">25.1 buffer</a></h2>
<p>Buffer video frames, and make them available to the filter chain.
</p>
<p>This source is mainly intended for a programmatic use, in particular
through the interface defined in ‘<tt>libavfilter/vsrc_buffer.h</tt>’.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>width</samp>’</dt>
<dd><p>The input video width.
</p>
</dd>
<dt> ‘<samp>height</samp>’</dt>
<dd><p>The input video height.
</p>
</dd>
<dt> ‘<samp>pix_fmt</samp>’</dt>
<dd><p>The name of the input video pixel format.
</p>
</dd>
<dt> ‘<samp>time_base</samp>’</dt>
<dd><p>The time base used for input timestamps.
</p>
</dd>
<dt> ‘<samp>sar</samp>’</dt>
<dd><p>The sample (pixel) aspect ratio of the input video.
</p>
</dd>
</dl>
<p>For example:
</p><table><tr><td> </td><td><pre class="example">buffer=width=320:height=240:pix_fmt=yuv410p:time_base=1/24:sar=1
</pre></td></tr></table>
<p>will instruct the source to accept video frames with size 320x240 and
with format "yuv410p", assuming 1/24 as the timestamps timebase and
square pixels (1:1 sample aspect ratio).
</p>
<a name="color"></a>
<h2 class="section"><a href="avconv.html#toc-color">25.2 color</a></h2>
<p>Provide an uniformly colored input.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>color</samp>’</dt>
<dd><p>Specify the color of the source. It can be the name of a color (case
insensitive match) or a 0xRRGGBB[AA] sequence, possibly followed by an
alpha specifier. The default value is "black".
</p>
</dd>
<dt> ‘<samp>size</samp>’</dt>
<dd><p>Specify the size of the sourced video, it may be a string of the form
<var>width</var>x<var>height</var>, or the name of a size abbreviation. The
default value is "320x240".
</p>
</dd>
<dt> ‘<samp>framerate</samp>’</dt>
<dd><p>Specify the frame rate of the sourced video, as the number of frames
generated per second. It has to be a string in the format
<var>frame_rate_num</var>/<var>frame_rate_den</var>, an integer number, a floating point
number or a valid video frame rate abbreviation. The default value is
"25".
</p>
</dd>
</dl>
<p>The following graph description will generate a red source
with an opacity of 0.2, with size "qcif" and a frame rate of 10
frames per second, which will be overlayed over the source connected
to the pad with identifier "in":
</p>
<table><tr><td> </td><td><pre class="example">"color=red@0.2:qcif:10 [color]; [in][color] overlay [out]"
</pre></td></tr></table>
<a name="movie"></a>
<h2 class="section"><a href="avconv.html#toc-movie">25.3 movie</a></h2>
<p>Read a video stream from a movie container.
</p>
<p>Note that this source is a hack that bypasses the standard input path. It can be
useful in applications that do not support arbitrary filter graphs, but its use
is discouraged in those that do. It should never be used with
<code>avconv</code>; the ‘<samp>-filter_complex</samp>’ option fully replaces it.
</p>
<p>It accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>filename</samp>’</dt>
<dd><p>The name of the resource to read (not necessarily a file; it can also be a
device or a stream accessed through some protocol).
</p>
</dd>
<dt> ‘<samp>format_name, f</samp>’</dt>
<dd><p>Specifies the format assumed for the movie to read, and can be either
the name of a container or an input device. If not specified, the
format is guessed from <var>movie_name</var> or by probing.
</p>
</dd>
<dt> ‘<samp>seek_point, sp</samp>’</dt>
<dd><p>Specifies the seek point in seconds. The frames will be output
starting from this seek point. The parameter is evaluated with
<code>av_strtod</code>, so the numerical value may be suffixed by an IS
postfix. The default value is "0".
</p>
</dd>
<dt> ‘<samp>stream_index, si</samp>’</dt>
<dd><p>Specifies the index of the video stream to read. If the value is -1,
the most suitable video stream will be automatically selected. The default
value is "-1".
</p>
</dd>
</dl>
<p>It allows overlaying a second video on top of the main input of
a filtergraph, as shown in this graph:
</p><table><tr><td> </td><td><pre class="example">input -----------> deltapts0 --> overlay --> output
^
|
movie --> scale--> deltapts1 -------+
</pre></td></tr></table>
<p>Some examples:
</p><table><tr><td> </td><td><pre class="example"># Skip 3.2 seconds from the start of the AVI file in.avi, and overlay it
# on top of the input labelled "in"
movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
[in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
# Read from a video4linux2 device, and overlay it on top of the input
# labelled "in"
movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
[in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
</pre></td></tr></table>
<a name="nullsrc"></a>
<h2 class="section"><a href="avconv.html#toc-nullsrc">25.4 nullsrc</a></h2>
<p>Null video source: never return images. It is mainly useful as a
template and to be employed in analysis / debugging tools.
</p>
<p>It accepts a string of the form
<var>width</var>:<var>height</var>:<var>timebase</var> as an optional parameter.
</p>
<p><var>width</var> and <var>height</var> specify the size of the configured
source. The default values of <var>width</var> and <var>height</var> are
respectively 352 and 288 (corresponding to the CIF size format).
</p>
<p><var>timebase</var> specifies an arithmetic expression representing a
timebase. The expression can contain the constants "PI", "E", "PHI", and
"AVTB" (the default timebase), and defaults to the value "AVTB".
</p>
<a name="frei0r_005fsrc"></a>
<h2 class="section"><a href="avconv.html#toc-frei0r_005fsrc">25.5 frei0r_src</a></h2>
<p>Provide a frei0r source.
</p>
<p>To enable compilation of this filter you need to install the frei0r
header and configure Libav with –enable-frei0r.
</p>
<p>This source accepts the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>size</samp>’</dt>
<dd><p>The size of the video to generate. It may be a string of the form
<var>width</var>x<var>height</var> or a frame size abbreviation.
</p>
</dd>
<dt> ‘<samp>framerate</samp>’</dt>
<dd><p>The framerate of the generated video. It may be a string of the form
<var>num</var>/<var>den</var> or a frame rate abbreviation.
</p>
</dd>
<dt> ‘<samp>filter_name</samp>’</dt>
<dd><p>The name to the frei0r source to load. For more information regarding frei0r and
how to set the parameters, read the <a href="#frei0r">frei0r</a> section in the video filters
documentation.
</p>
</dd>
<dt> ‘<samp>filter_params</samp>’</dt>
<dd><p>A ’|’-separated list of parameters to pass to the frei0r source.
</p>
</dd>
</dl>
<p>An example:
</p><table><tr><td> </td><td><pre class="example"># Generate a frei0r partik0l source with size 200x200 and framerate 10
# which is overlayed on the overlay filter main input
frei0r_src=size=200x200:framerate=10:filter_name=partik0l:filter_params=1234 [overlay]; [in][overlay] overlay
</pre></td></tr></table>
<a name="rgbtestsrc_002c-testsrc"></a>
<h2 class="section"><a href="avconv.html#toc-rgbtestsrc_002c-testsrc">25.6 rgbtestsrc, testsrc</a></h2>
<p>The <code>rgbtestsrc</code> source generates an RGB test pattern useful for
detecting RGB vs BGR issues. You should see a red, green and blue
stripe from top to bottom.
</p>
<p>The <code>testsrc</code> source generates a test video pattern, showing a
color pattern, a scrolling gradient and a timestamp. This is mainly
intended for testing purposes.
</p>
<p>The sources accept the following parameters:
</p>
<dl compact="compact">
<dt> ‘<samp>size, s</samp>’</dt>
<dd><p>Specify the size of the sourced video, it may be a string of the form
<var>width</var>x<var>height</var>, or the name of a size abbreviation. The
default value is "320x240".
</p>
</dd>
<dt> ‘<samp>rate, r</samp>’</dt>
<dd><p>Specify the frame rate of the sourced video, as the number of frames
generated per second. It has to be a string in the format
<var>frame_rate_num</var>/<var>frame_rate_den</var>, an integer number, a floating point
number or a valid video frame rate abbreviation. The default value is
"25".
</p>
</dd>
<dt> ‘<samp>sar</samp>’</dt>
<dd><p>Set the sample aspect ratio of the sourced video.
</p>
</dd>
<dt> ‘<samp>duration</samp>’</dt>
<dd><p>Set the video duration of the sourced video. The accepted syntax is:
</p><table><tr><td> </td><td><pre class="example">[-]HH[:MM[:SS[.m...]]]
[-]S+[.m...]
</pre></td></tr></table>
<p>Also see the the <code>av_parse_time()</code> function.
</p>
<p>If not specified, or the expressed duration is negative, the video is
supposed to be generated forever.
</p></dd>
</dl>
<p>For example the following:
</p><table><tr><td> </td><td><pre class="example">testsrc=duration=5.3:size=qcif:rate=10
</pre></td></tr></table>
<p>will generate a video with a duration of 5.3 seconds, with size
176x144 and a framerate of 10 frames per second.
</p>
<a name="Video-Sinks"></a>
<h1 class="chapter"><a href="avconv.html#toc-Video-Sinks">26. Video Sinks</a></h1>
<p>Below is a description of the currently available video sinks.
</p>
<a name="buffersink"></a>
<h2 class="section"><a href="avconv.html#toc-buffersink">26.1 buffersink</a></h2>
<p>Buffer video frames, and make them available to the end of the filter
graph.
</p>
<p>This sink is intended for programmatic use through the interface defined in
‘<tt>libavfilter/buffersink.h</tt>’.
</p>
<a name="nullsink"></a>
<h2 class="section"><a href="avconv.html#toc-nullsink">26.2 nullsink</a></h2>
<p>Null video sink: do absolutely nothing with the input video. It is
mainly useful as a template and for use in analysis / debugging
tools.
</p>
<a name="Metadata"></a>
<h1 class="chapter"><a href="avconv.html#toc-Metadata">27. Metadata</a></h1>
<p>Libav is able to dump metadata from media files into a simple UTF-8-encoded
INI-like text file and then load it back using the metadata muxer/demuxer.
</p>
<p>The file format is as follows:
</p><ol>
<li>
A file consists of a header and a number of metadata tags divided into sections,
each on its own line.
</li><li>
The header is a ’;FFMETADATA’ string, followed by a version number (now 1).
</li><li>
Metadata tags are of the form ’key=value’
</li><li>
Immediately after header follows global metadata
</li><li>
After global metadata there may be sections with per-stream/per-chapter
metadata.
</li><li>
A section starts with the section name in uppercase (i.e. STREAM or CHAPTER) in
brackets (’[’, ’]’) and ends with next section or end of file.
</li><li>
At the beginning of a chapter section there may be an optional timebase to be
used for start/end values. It must be in form ’TIMEBASE=num/den’, where num and
den are integers. If the timebase is missing then start/end times are assumed to
be in milliseconds.
Next a chapter section must contain chapter start and end times in form
’START=num’, ’END=num’, where num is a positive integer.
</li><li>
Empty lines and lines starting with ’;’ or ’#’ are ignored.
</li><li>
Metadata keys or values containing special characters (’=’, ’;’, ’#’, ’\’ and a
newline) must be escaped with a backslash ’\’.
</li><li>
Note that whitespace in metadata (e.g. foo = bar) is considered to be a part of
the tag (in the example above key is ’foo ’, value is ’ bar’).
</li></ol>
<p>A ffmetadata file might look like this:
</p><table><tr><td> </td><td><pre class="example">;FFMETADATA1
title=bike\\shed
;this is a comment
artist=Libav troll team
[CHAPTER]
TIMEBASE=1/1000
START=0
#chapter ends at 0:01:00
END=60000
title=chapter \#1
[STREAM]
title=multi\
line
</pre></td></tr></table>
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