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<div class="refentry" title="alpass">
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<h2>
<span class="refentrytitle">alpass</span>
</h2>
<p>alpass —
Reverberates an input signal with a flat frequency response.
</p>
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<div class="refsect1" title="Description">
<a id="idp13428792"></a>
<h2>Description</h2>
<p>
Reverberates an input signal with a flat frequency response.
</p>
</div>
<div class="refsect1" title="Syntax">
<a id="idp13429552"></a>
<h2>Syntax</h2>
<pre class="synopsis">ares <span class="command"><strong>alpass</strong></span> asig, krvt, ilpt [, iskip] [, insmps]</pre>
</div>
<div class="refsect1" title="Initialization">
<a id="idp13447080"></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 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 4<span class="emphasis"><em>n</em></span>*<span class="emphasis"><em>sr</em></span> bytes. The 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" title="Performance">
<a id="idp13491416"></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 the 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 will begin to appear immediately.
</p>
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<div class="refsect1" title="Examples">
<a id="idp13493672"></a>
<h2>Examples</h2>
<p>
Here is an example of the alpass opcode. It uses the file <a class="ulink" href="examples/alpass.csd" target="_top"><em class="citetitle">alpass.csd</em></a>.
</p>
<div class="example">
<a id="idp13494648"></a>
<p class="title">
<strong>Example 44. Example of the alpass 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>
<pre class="programlisting">
<span class="csdtag"><CsoundSynthesizer></span>
<span class="csdtag"><CsOptions></span>
<span class="comment">; Select audio/midi flags here according to platform</span>
-odac <span class="comment">;;;RT audio out</span>
<span class="comment">;-iadc ;;;uncomment -iadc if RT audio input is needed too</span>
<span class="comment">; For Non-realtime ouput leave only the line below:</span>
<span class="comment">; -o alpass.wav -W ;;; for file output any platform</span>
<span class="csdtag"></CsOptions></span>
<span class="csdtag"><CsInstruments></span>
<span class="ohdr">sr</span> <span class="op">=</span> 44100
<span class="ohdr">ksmps</span> <span class="op">=</span> 32
<span class="ohdr">nchnls</span> <span class="op">=</span> 2
<span class="ohdr">0dbfs</span> <span class="op">=</span> 1
gamix <span class="opc">init</span> 0
<span class="oblock">instr</span> 1
kcps <span class="opc">expon</span> p4, p3, p5
asig <span class="opc">vco2</span> 0.6, kcps
<span class="opc">outs</span> asig, asig
gamix <span class="op">=</span> gamix <span class="op">+</span> asig
<span class="oblock">endin</span>
<span class="oblock">instr</span> 99
krvt <span class="op">=</span> 3.5
ilpt <span class="op">=</span> 0.1
aleft <span class="opc">alpass</span> gamix, krvt<span class="op">*</span>1.5, ilpt
aright <span class="opc">alpass</span> gamix, krvt, ilpt<span class="op">*</span>2
<span class="opc">outs</span> aleft, aright
gamix <span class="op">=</span> 0 <span class="comment">; clear mixer</span>
<span class="oblock">endin</span>
<span class="csdtag"></CsInstruments></span>
<span class="csdtag"><CsScore></span>
<span class="stamnt">i</span> 1 0 3 20 2000
<span class="stamnt">i</span> 99 0 8
<span class="stamnt">e</span>
<span class="csdtag"></CsScore></span>
<span class="csdtag"></CsoundSynthesizer></span>
</pre>
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<p><br class="example-break" />
</p>
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<div class="refsect1" title="See Also">
<a id="idp13496920"></a>
<h2>See Also</h2>
<p>
<a class="link" href="comb.html" title="comb"><em class="citetitle">comb</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" title="Credits">
<a id="idp13499432"></a>
<h2>Credits</h2>
<p>
</p>
<table border="0" summary="Simple list" class="simplelist">
<tr>
<td>Author: William <span class="quote">“<span class="quote">Pete</span>”</span> Moss (<span class="emphasis"><em>vcomb</em></span> and <span class="emphasis"><em>valpass</em></span>)</td>
</tr>
<tr>
<td>University of Texas at Austin</td>
</tr>
<tr>
<td>Austin, Texas USA</td>
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<td>January 2002</td>
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