opcodes/specfilt.xml


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<refentry id="specfilt">
<indexterm id="IndexSpecfilt"><primary>specfilt</primary></indexterm>
  <refentryinfo><title>Spectral Processing:Non-Standard</title></refentryinfo>
  <refmeta>
    <refentrytitle>specfilt</refentrytitle>
  </refmeta>


  <refnamediv>
    <refname>specfilt</refname>
    <refpurpose>
      Filters each channel of an input spectrum.
    </refpurpose>
  </refnamediv>
 
  <refsect1>
    <title>Description</title>
    <para>
      Filters each channel of an input spectrum.
    </para>
  </refsect1>
 
  <refsect1>
    <title>Syntax</title>
    <synopsis>wsig <command>specfilt</command> wsigin, ifhtim</synopsis>
  </refsect1>
 
  <refsect1>
    <title>Initialization</title>
    <para>
      <emphasis>ifhtim</emphasis> --  half-time constant.
    </para>
  </refsect1>
 
  <refsect1>
    <title>Performance</title>
    <para>
      <emphasis>wsigin</emphasis> --  the input spectrum.
    </para>

    <para>
      Filters each channel of an input spectrum. At each new frame of <emphasis>wsigin</emphasis>, each magnitude value is injected into a 1st-order lowpass recursive filter, whose half-time constant has been initially set by sampling the ftable <emphasis>ifhtim</emphasis> across the (logarithmic) frequency space of the input spectrum. This unit effectively applies a <emphasis>persistence</emphasis> factor to the data occurring in each spectral channel, and is useful for simulating the <emphasis>energy integration</emphasis> that occurs during auditory perception. It may also be used as a time-attenuated running <emphasis>histogram</emphasis> of the spectral distribution.
    </para>
  </refsect1>
 
  <refsect1>
    <title>Examples</title>
    <para>
      <informalexample>
        <programlisting>
  wsig2    <emphasis role="opc">specdiff</emphasis>    wsig1         <emphasis role="comment">; sense onsets</emphasis>
  wsig3    <emphasis role="opc">specfilt</emphasis>    wsig2, 2      <emphasis role="comment">; absorb slowly</emphasis>
           <emphasis role="opc">specdisp</emphasis>    wsig2, 0.1    <emphasis role="comment">; &amp; display both spectra</emphasis>
           <emphasis role="opc">specdisp</emphasis>    wsig3, 0.1</programlisting>
      </informalexample>
    </para>
  </refsect1>

  <refsect1>
    <title>See Also</title>
    <para>
      <link linkend="specaddm"><citetitle>specaddm</citetitle></link>,
      <link linkend="specdiff"><citetitle>specdiff</citetitle></link>,
      <link linkend="spechist"><citetitle>spechist</citetitle></link>,
      <link linkend="specscal"><citetitle>specscal</citetitle></link>
    </para>
  </refsect1>
</refentry>