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<h2>
<span class="refentrytitle">alpass</span>
</h2>
<p>alpass —
Reverberates an input signal with a flat frequency response.
</p>
</div>
<div class="refsect1">
<a id="idm281472951751688"></a>
<h2>Description</h2>
<p>
Reverberates an input signal with a flat frequency response.
</p>
</div>
<div class="refsect1">
<a id="idm281472951740072"></a>
<h2>Syntax</h2>
<pre class="synopsis">ares <span class="command"><strong>alpass</strong></span> asig, xrvt, ilpt [, iskip] [, insmps]</pre>
</div>
<div class="refsect1">
<a id="idm281472951737816"></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">
<a id="idm281472951658104"></a>
<h2>Performance</h2>
<p>
<span class="emphasis"><em>xrvt</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>xrvt</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">
<a id="idm281472951654488"></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="idm281472951652632"></a>
<p class="title">
<strong>Example 50. 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>
<div class="refsect1">
<a id="idm281472787279400"></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 alpass.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">100</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>
a<span class="n">cps</span> <span class="nb">expon</span> <span class="nb">p4</span><span class="p">,</span> <span class="nb">p3</span><span class="p">,</span> <span class="nb">p5</span>
a<span class="n">sig</span> <span class="nb">vco</span> <span class="mf">0.6</span><span class="p">,</span> a<span class="n">cps</span><span class="p">,</span> <span class="mi">1</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>
a<span class="n">rvt1</span> <span class="nb">line</span> <span class="mf">3.5</span><span class="o">*</span><span class="mf">1.5</span><span class="p">,</span> <span class="nb">p3</span><span class="p">,</span> <span class="mi">6</span>
a<span class="n">rvt2</span> <span class="nb">line</span> <span class="mf">3.5</span><span class="p">,</span> <span class="nb">p3</span><span class="p">,</span> <span class="mi">4</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">alpass</span> ga<span class="n">mix</span><span class="p">,</span> a<span class="n">rvt1</span><span class="p">,</span> i<span class="n">lpt</span>
a<span class="n">right</span> <span class="nb">alpass</span> ga<span class="n">mix</span><span class="p">,</span> a<span class="n">rvt2</span><span class="p">,</span> i<span class="n">lpt</span><span class="o">*</span><span class="mi">2</span>
<span class="nb">outs</span> a<span class="n">left</span><span class="p">,</span> a<span class="n">right</span>
ga<span class="n">mix</span> <span class="o">=</span> <span class="mi">0</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">f</span><span class="mi">1</span> <span class="mi">0</span> <span class="mi">4096</span> <span class="mi">10</span> <span class="mi">1</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">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="idm281472951648408"></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">
<a id="idm281472951643416"></a>
<h2>Credits</h2>
<p>Audio rate parameter introduced in version 6.02</p>
<p>November 2013.</p>
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