/usr/share/doc/gstreamer0.10-doc/manual/html/chapter-queryevents.html is in gstreamer0.10-doc 0.10.36-1.5ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd">
<HTML
><HEAD
><TITLE
>Position tracking and seeking</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.79;charset=UTF-8"><LINK
REL="HOME"
TITLE="GStreamer Application Development Manual (0.10.36)"
HREF="index.html"><LINK
REL="UP"
TITLE="Advanced GStreamer concepts"
HREF="part-advanced.html"><LINK
REL="PREVIOUS"
TITLE="Advanced GStreamer concepts"
HREF="part-advanced.html"><LINK
REL="NEXT"
TITLE="Events: seeking (and more)"
HREF="section-eventsseek.html"></HEAD
><BODY
CLASS="chapter"
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#840084"
ALINK="#0000FF"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
><SPAN
CLASS="application"
>GStreamer</SPAN
> Application Development Manual (0.10.36)</TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="part-advanced.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
></TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="section-eventsseek.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="chapter"
><H1
><A
NAME="chapter-queryevents"
></A
>Chapter 11. Position tracking and seeking</H1
><P
> So far, we've looked at how to create a pipeline to do media processing
and how to make it run. Most application developers will be interested
in providing feedback to the user on media progress. Media players, for
example, will want to show a slider showing the progress in the song,
and usually also a label indicating stream length. Transcoding
applications will want to show a progress bar on how much percent of
the task is done. <SPAN
CLASS="application"
>GStreamer</SPAN
> has built-in support for doing all this
using a concept known as <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>querying</I
></SPAN
>. Since seeking
is very similar, it will be discussed here as well. Seeking is done
using the concept of <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>events</I
></SPAN
>.
</P
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="section-querying"
>11.1. Querying: getting the position or length of a stream</A
></H1
><P
> Querying is defined as requesting a specific stream property related
to progress tracking. This includes getting the length of a stream (if
available) or getting the current position. Those stream properties
can be retrieved in various formats such as time, audio samples, video
frames or bytes. The function most commonly used for this is
<CODE
CLASS="function"
>gst_element_query ()</CODE
>, although some convenience
wrappers are provided as well (such as
<CODE
CLASS="function"
>gst_element_query_position ()</CODE
> and
<CODE
CLASS="function"
>gst_element_query_duration ()</CODE
>). You can generally
query the pipeline directly, and it'll figure out the internal details
for you, like which element to query.
</P
><P
> Internally, queries will be sent to the sinks, and
<SPAN
CLASS="QUOTE"
>"dispatched"</SPAN
> backwards until one element can handle it;
that result will be sent back to the function caller. Usually, that
is the demuxer, although with live sources (from a webcam), it is the
source itself.
</P
><PRE
CLASS="programlisting"
>
#include <gst/gst.h>
static gboolean
cb_print_position (GstElement *pipeline)
{
GstFormat fmt = GST_FORMAT_TIME;
gint64 pos, len;
if (gst_element_query_position (pipeline, &fmt, &pos)
&& gst_element_query_duration (pipeline, &fmt, &len)) {
g_print ("Time: %" GST_TIME_FORMAT " / %" GST_TIME_FORMAT "\r",
GST_TIME_ARGS (pos), GST_TIME_ARGS (len));
}
/* call me again */
return TRUE;
}
gint
main (gint argc,
gchar *argv[])
{
GstElement *pipeline;
[..]
/* run pipeline */
g_timeout_add (200, (GSourceFunc) cb_print_position, pipeline);
g_main_loop_run (loop);
[..]
}
</PRE
></DIV
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="part-advanced.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="index.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="section-eventsseek.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>Advanced <SPAN
CLASS="application"
>GStreamer</SPAN
> concepts</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="part-advanced.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>Events: seeking (and more)</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>
|