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<h2>
<span class="refentrytitle">comb</span>
</h2>
<p>comb —
Reverberates an input signal with a <span class="quote">“<span class="quote">colored</span>”</span> frequency response.
</p>
</div>
<div class="refsect1">
<a id="idm281472946096600"></a>
<h2>Description</h2>
<p>
Reverberates an input signal with a <span class="quote">“<span class="quote">colored</span>”</span> frequency response.
</p>
</div>
<div class="refsect1">
<a id="idm281472946094840"></a>
<h2>Syntax</h2>
<pre class="synopsis">ares <span class="command"><strong>comb</strong></span> asig, krvt, ilpt [, iskip] [, insmps]</pre>
</div>
<div class="refsect1">
<a id="idm281472946023384"></a>
<h2>Initialization</h2>
<p>
<span class="emphasis"><em>ilpt</em></span> -- loop time in seconds, which
determines the <span class="quote">“<span class="quote">echo density</span>”</span> of the
reverberation. This in turn characterizes the
<span class="quote">“<span class="quote">color</span>”</span> of the <span class="emphasis"><em>comb</em></span> filter
whose frequency response curve will contain
<span class="emphasis"><em>ilpt</em></span> * <span class="emphasis"><em>sr</em></span>/2 peaks
spaced evenly between 0 and <span class="emphasis"><em>sr</em></span>/2 (the
Nyquist frequency). Loop time can be as large as available
memory will permit. The space required for an
<span class="emphasis"><em>n</em></span> second loop is
<span class="emphasis"><em>n</em></span>*<span class="emphasis"><em>sr</em></span> floating or
double numbers (usually 4 or 8 bytes). Delay space is allocated
and returned as in <a class="link" href="delay.html" title="delay"><em class="citetitle">delay</em></a>.
</p>
<p>
<span class="emphasis"><em>iskip</em></span> (optional, default=0) -- initial disposition of delay-loop data space (cf. <a class="link" href="reson.html" title="reson"><em class="citetitle">reson</em></a>). The default value is 0.
</p>
<p>
<span class="emphasis"><em>insmps</em></span> (optional, default=0) -- delay amount, as a number of samples.
</p>
</div>
<div class="refsect1">
<a id="idm281472946013528"></a>
<h2>Performance</h2>
<p>
<span class="emphasis"><em>krvt</em></span> -- the reverberation time (defined as the time in seconds for a signal to decay to 1/1000, or 60dB down from its original amplitude).
</p>
<p>
This filter reiterates input with an echo density determined by loop time <span class="emphasis"><em>ilpt</em></span>. The attenuation rate is independent and is determined by <span class="emphasis"><em>krvt</em></span>, the reverberation time (defined as the time in seconds for a signal to decay to 1/1000, or 60dB down from its original amplitude). Output from a comb filter will appear only after <span class="emphasis"><em>ilpt</em></span> seconds.
</p>
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<div class="refsect1">
<a id="idm281472946009608"></a>
<h2>Examples</h2>
<p>
Here is an example of the comb opcode. It uses the file <a class="ulink" href="examples/comb.csd" target="_top"><em class="citetitle">comb.csd</em></a>.
</p>
<div class="example">
<a id="idm281472946007752"></a>
<p class="title">
<strong>Example 138. Example of the comb opcode.</strong>
</p>
<div class="example-contents">
<p>See the sections <a class="link" href="UsingRealTime.html" title="Real-Time Audio"><em class="citetitle">Real-time Audio</em></a> and <a class="link" href="CommandFlags.html" title="Csound command line"><em class="citetitle">Command Line Flags</em></a> for more information on using command line flags.</p>
<div class="refsect1">
<a id="idm281472779217128"></a>
<pre class="programlisting">
<span class="nt"><CsoundSynthesizer></span>
<span class="nt"><CsOptions></span>
<span class="c1">; Select audio/midi flags here according to platform</span>
-odac <span class="c1">;;;RT audio out</span>
<span class="c1">;-iadc ;;;uncomment -iadc if RT audio input is needed too</span>
<span class="c1">; For Non-realtime ouput leave only the line below:</span>
<span class="c1">; -o comb.wav -W ;;; for file output any platform</span>
<span class="nt"></CsOptions></span>
<span class="nt"><CsInstruments></span>
<span class="vg">sr</span> <span class="o">=</span> <span class="mi">44100</span>
<span class="vg">ksmps</span> <span class="o">=</span> <span class="mi">32</span>
<span class="vg">nchnls</span> <span class="o">=</span> <span class="mi">2</span>
<span class="vg">0dbfs</span> <span class="o">=</span> <span class="mi">1</span>
ga<span class="n">mix</span> <span class="nb">init</span> <span class="mi">0</span>
<span class="kd">instr</span> <span class="nf">1</span>
k<span class="n">cps</span> <span class="nb">expon</span> <span class="nb">p5</span><span class="p">,</span> <span class="nb">p3</span><span class="p">,</span> <span class="nb">p4</span>
a<span class="n">sig</span> <span class="nb">vco2</span> <span class="mf">0.3</span><span class="p">,</span> k<span class="n">cps</span>
<span class="nb">outs</span> a<span class="n">sig</span><span class="p">,</span> a<span class="n">sig</span>
ga<span class="n">mix</span> <span class="o">=</span> ga<span class="n">mix</span> <span class="o">+</span> a<span class="n">sig</span>
<span class="kd">endin</span>
<span class="kd">instr</span> <span class="nf">99</span>
k<span class="n">rvt</span> <span class="o">=</span> <span class="mf">3.5</span>
i<span class="n">lpt</span> <span class="o">=</span> <span class="mf">0.1</span>
a<span class="n">left</span> <span class="nb">comb</span> ga<span class="n">mix</span><span class="p">,</span> k<span class="n">rvt</span><span class="p">,</span> i<span class="n">lpt</span>
a<span class="n">right</span> <span class="nb">comb</span> ga<span class="n">mix</span><span class="p">,</span> k<span class="n">rvt</span><span class="p">,</span> i<span class="n">lpt</span><span class="o">*</span><span class="mf">.2</span>
<span class="nb">outs</span> a<span class="n">left</span><span class="p">,</span> a<span class="n">right</span>
<span class="nb">clear</span> ga<span class="n">mix</span> <span class="c1">; clear mixer</span>
<span class="kd">endin</span>
<span class="nt"></CsInstruments></span>
<span class="nt"><CsScore></span>
<span class="nb">i</span> <span class="mi">1</span> <span class="mi">0</span> <span class="mi">3</span> <span class="mi">20</span> <span class="mi">2000</span>
<span class="nb">i</span> <span class="mi">1</span> <span class="mi">5</span> <span class="mf">.01</span> <span class="mi">440</span> <span class="mi">440</span>
<span class="nb">i</span> <span class="mi">99</span> <span class="mi">0</span> <span class="mi">8</span>
<span class="nb">e</span>
<span class="nt"></CsScore></span>
<span class="nt"></CsoundSynthesizer></span>
</pre>
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<p><br class="example-break" />
</p>
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<div class="refsect1">
<a id="idm281472946003432"></a>
<h2>See Also</h2>
<p>
<a class="link" href="alpass.html" title="alpass"><em class="citetitle">alpass</em></a>,
<a class="link" href="reverb.html" title="reverb"><em class="citetitle">reverb</em></a>,
<a class="link" href="valpass.html" title="valpass"><em class="citetitle">valpass</em></a>,
<a class="link" href="vcomb.html" title="vcomb"><em class="citetitle">vcomb</em></a>
</p>
</div>
<div class="refsect1">
<a id="idm281472945998440"></a>
<h2>Credits</h2>
<p>
</p>
<table border="0" summary="Simple list" class="simplelist">
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<td>Barry L. Vercoe</td>
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