/usr/lib/lv2/decay-swh.lv2/plugin.ttl is in swh-lv2 1.0.16+git20160519~repack0-3.
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 | @prefix : <http://lv2plug.in/ns/lv2core#> .
@prefix swh: <http://plugin.org.uk/swh-plugins/> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
@prefix doap: <http://usefulinc.com/ns/doap#> .
@prefix swhext: <http://plugin.org.uk/extensions#> .
@prefix pg: <http://lv2plug.in/ns/ext/port-groups#> .
@prefix pprops: <http://lv2plug.in/ns/ext/port-props#> .
swh:decay a :Plugin ;
   a :UtilityPlugin ;
   doap:name "Exponential signal decay" ;
   doap:maintainer [
      foaf:name "Steve Harris";
      foaf:homepage <http://plugin.org.uk/> ;
      foaf:mbox <mailto:steve@plugin.org.uk> ;
   ] ;
   doap:license <http://usefulinc.com/doap/licenses/gpl> ;
   :documentation <http://plugin.org.uk/ladspa-swh/docs/ladspa-swh.html#decay> ;
   :pluginProperty :hardRtCapable ;
    
   :port [
     a :InputPort, :AudioPort ;
     :name "Input" ;
     :index 0 ;
     :symbol "in" ;
   ] ;
  
   :port [
     a :OutputPort, :AudioPort ;
     :name "Output" ;
     :index 1 ;
     :symbol "out" ;
   ] ;
  
   :port [
     a :InputPort, :ControlPort ;
     :name "Decay Time (s)" ;
     :index 2 ;
     :symbol "decay_time" ;
     :minimum 0 ;
     :maximum 10 ;
     
     :default 1.0 ;
   ] ;
  
   swhext:code """
      #include "ladspa-util.h"
      #define LOG001 -6.9077552789f
    """ ;
   swhext:callback [
     swhext:event "instantiate" ;
     swhext:code """
      sample_rate = s_rate;
    """ ;
   ] ;
  
   swhext:callback [
     swhext:event "activate" ;
     swhext:code """
      plugin_data->b = 0.f;
      plugin_data->y = 0.f;
      plugin_data->last_decay_time = 0.f;
      plugin_data->first_time = 0;
    """ ;
   ] ;
  
   swhext:callback [
     swhext:event "run" ;
     swhext:code """
      int i;
      if (first_time) {
        plugin_data->last_decay_time = decay_time;
        plugin_data->b = decay_time == 0.f ? 0.f : exp (LOG001 / (decay_time * sample_rate));
        plugin_data->first_time = 0;
      }
      if (decay_time == plugin_data->last_decay_time) {
        if (b == 0.f)
          for (i=0; i<sample_count; i++)
            out[i] = y = in[i];
        else
          for (i=0; i<sample_count; i++)
            out[i] = y = in[i] + b * y;
      } else {
        LADSPA_Data b_slope;
        plugin_data->b = decay_time == 0.f ? 0.f : exp (LOG001 / (decay_time * sample_rate));
        b_slope = (plugin_data->b - b) / sample_count;
        for (i=0; i<sample_count; i++) {
          buffer_write(out[i], y = in[i] + b * y);
          b += b_slope;
        }
        plugin_data->last_decay_time = decay_time;
      }
      
      plugin_data->y = y;
    """ ;
   ] ;
  
   swhext:createdBy <http://plugin.org.uk/swh-plugins/toTurtle.xsl> .
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