decay_1886.xml

<?xml version="1.0"?>
<!DOCTYPE ladspa SYSTEM "ladspa-swh.dtd">
<?xml-stylesheet href="ladspa.css" type="text/css"?>

<ladspa>
  <global>
    <meta name="maker" value="Andy Wingo &lt;wingo at pobox dot com&gt;"/>
    <meta name="copyright" value="GPL"/>
    <meta name="properties" value="HARD_RT_CAPABLE"/>
    <code><![CDATA[
      #include "ladspa-util.h"

      #define LOG001 -6.9077552789f
    ]]></code>
  </global>

  <!-- ******   DECAY   ****** -->

  <plugin label="decay" id="1886" class="UtilityPlugin">
    <name>Exponential signal decay</name>
    <p>Based on work by James McCartney in SuperCollider.</p>
    
    <callback event="instantiate"><![CDATA[
      sample_rate = s_rate;

      // Uninitialized variables
      b = 0;
      first_time = 0;
      last_decay_time = 0;
      y = 0;
    ]]></callback>
    
    <callback event="activate"><![CDATA[
      b = 0.f;
      y = 0.f;
      last_decay_time = 0.f;
      first_time = 0;
    ]]></callback>
    
    <callback event="run"><![CDATA[
      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 == 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;
    ]]></callback>

    <port label="in" dir="input" type="audio">
      <name>Input</name>
    </port>

    <port label="out" dir="output" type="audio">
      <name>Output</name>
    </port>

    <port label="decay_time" dir="input" type="control" hint="default_1">
      <name>Decay Time (s)</name>
      <range min="0"/>
      <p>
       Time for the echoes to decay by 60 decibels.
      </p>
    </port>

    <instance-data label="y" type="LADSPA_Data" />
    <instance-data label="b" type="LADSPA_Data" />
    <instance-data label="last_decay_time" type="LADSPA_Data" />
    <instance-data label="sample_rate" type="LADSPA_Data" />
    <instance-data label="first_time" type="char" />
  </plugin>
</ladspa>