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<a id="dconv"></a>
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<a id="IndexDconv" class="indexterm"></a>
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<h2>
<span class="refentrytitle">dconv</span>
</h2>
<p>dconv —
A direct convolution opcode.
</p>
</div>
<div class="refsect1">
<a id="idm281472942913848"></a>
<h2>Description</h2>
<p>
A direct convolution opcode.
</p>
</div>
<div class="refsect1">
<a id="idm281472942910280"></a>
<h2>Syntax</h2>
<pre class="synopsis">ares <span class="command"><strong>dconv</strong></span> asig, isize, ifn</pre>
</div>
<div class="refsect1">
<a id="idm281472942908072"></a>
<h2>Initialization</h2>
<p>
<span class="emphasis"><em>isize</em></span> -- the size of the convolution buffer to use. If the buffer size is smaller than the size of <span class="emphasis"><em>ifn</em></span>, then only the first <span class="emphasis"><em>isize</em></span> values will be used from the table.
</p>
<p>
<span class="emphasis"><em>ifn</em></span> -- table number of a stored function containing the impulse response for convolution.
</p>
</div>
<div class="refsect1">
<a id="idm281472942844536"></a>
<h2>Performance</h2>
<p>
Rather than the analysis/resynthesis method of the <span class="emphasis"><em>convolve</em></span> opcode, <span class="emphasis"><em>dconv</em></span> uses direct convolution to create the result. For small tables it can do this quite efficiently, however larger table require much more time to run. <span class="emphasis"><em>dconv</em></span> does (<span class="emphasis"><em>isize</em></span> * <span class="emphasis"><em>ksmps</em></span>) multiplies on every k-cycle. Therefore, reverb and delay effects are best done with other opcodes (unless the times are short).
</p>
<p>
<span class="emphasis"><em>dconv</em></span> was designed to be used with time varying tables to facilitate new realtime filtering capabilities.
</p>
</div>
<div class="refsect1">
<a id="idm281472942839976"></a>
<h2>Examples</h2>
<p>
Here is an example of the dconv opcode. It uses the file <a class="ulink" href="examples/dconv.csd" target="_top"><em class="citetitle">dconv.csd</em></a>.
</p>
<div class="example">
<a id="idm281472942838120"></a>
<p class="title">
<strong>Example 188. Example of the dconv 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="idm281472775765752"></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>
<span class="c1">; Audio out Audio in No messages</span>
-odac -iadc -d <span class="c1">;;;RT audio I/O</span>
<span class="c1">; For Non-realtime ouput leave only the line below:</span>
<span class="c1">; -o dconv.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">kr</span> <span class="o">=</span> <span class="mi">4410</span>
<span class="vg">ksmps</span> <span class="o">=</span> <span class="mi">10</span>
<span class="vg">nchnls</span> <span class="o">=</span> <span class="mi">1</span>
<span class="cp">#define</span> <span class="cp">RANDI</span>(<span class="cp">A</span><span class="p">)</span> <span class="p">#</span><span class="cp">kout randi 1, kfq, $A*.001+iseed, 1
tablew kout, $A, itable</span><span class="p">#</span>
<span class="kd">instr</span> <span class="nf">1</span>
i<span class="n">table</span> <span class="nb">init</span> <span class="mi">1</span>
i<span class="n">seed</span> <span class="nb">init</span> <span class="mf">.6</span>
i<span class="n">size</span> <span class="nb">init</span> <span class="nb">ftlen</span><span class="p">(</span>i<span class="n">table</span><span class="p">)</span>
k<span class="n">fq</span> <span class="nb">line</span> <span class="mi">1</span><span class="p">,</span> <span class="nb">p3</span><span class="p">,</span> <span class="mi">10</span>
<span class="cp">$RANDI</span><span class="p">(</span><span class="cp">0</span><span class="p">)</span>
<span class="cp">$RANDI</span><span class="p">(</span><span class="cp">1</span><span class="p">)</span>
<span class="cp">$RANDI</span><span class="p">(</span><span class="cp">2</span><span class="p">)</span>
<span class="cp">$RANDI</span><span class="p">(</span><span class="cp">3</span><span class="p">)</span>
<span class="cp">$RANDI</span><span class="p">(</span><span class="cp">4</span><span class="p">)</span>
<span class="cp">$RANDI</span><span class="p">(</span><span class="cp">5</span><span class="p">)</span>
<span class="cp">$RANDI</span><span class="p">(</span><span class="cp">6</span><span class="p">)</span>
<span class="cp">$RANDI</span><span class="p">(</span><span class="cp">7</span><span class="p">)</span>
<span class="cp">$RANDI</span><span class="p">(</span><span class="cp">8</span><span class="p">)</span>
<span class="cp">$RANDI</span><span class="p">(</span><span class="cp">9</span><span class="p">)</span>
<span class="cp">$RANDI</span><span class="p">(</span><span class="cp">10</span><span class="p">)</span>
<span class="cp">$RANDI</span><span class="p">(</span><span class="cp">11</span><span class="p">)</span>
<span class="cp">$RANDI</span><span class="p">(</span><span class="cp">12</span><span class="p">)</span>
<span class="cp">$RANDI</span><span class="p">(</span><span class="cp">13</span><span class="p">)</span>
<span class="cp">$RANDI</span><span class="p">(</span><span class="cp">14</span><span class="p">)</span>
<span class="cp">$RANDI</span><span class="p">(</span><span class="cp">15</span><span class="p">)</span>
a<span class="n">sig</span> <span class="nb">rand</span> <span class="mi">10000</span><span class="p">,</span> <span class="mf">.5</span><span class="p">,</span> <span class="mi">1</span>
a<span class="n">sig</span> <span class="nb">butlp</span> a<span class="n">sig</span><span class="p">,</span> <span class="mi">5000</span>
a<span class="n">sig</span> <span class="nb">dconv</span> a<span class="n">sig</span><span class="p">,</span> i<span class="n">size</span><span class="p">,</span> i<span class="n">table</span>
<span class="nb">out</span> a<span class="n">sig</span> <span class="o">*</span><span class="mf">.5</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">16</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">10</span>
<span class="nb">e</span>
<span class="nt"></CsScore></span>
<span class="nt"></CsoundSynthesizer></span>
</pre>
</div>
</div>
</div>
<p><br class="example-break" />
</p>
</div>
<div class="refsect1">
<a id="idm281472942833928"></a>
<h2>See also</h2>
<p>
<a class="link" href="pconvolve.html" title="pconvolve"><em class="citetitle">pconvolve</em></a>,
<a class="link" href="convolve.html" title="convolve"><em class="citetitle">convolve</em></a>,
<a class="link" href="ftconv.html" title="ftconv"><em class="citetitle">ftconv</em></a>
</p>
</div>
<div class="refsect1">
<a id="idm281472942829960"></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</td>
</tr>
<tr>
<td>2001</td>
</tr>
</table>
<p>
</p>
<p>New in version 4.12</p>
</div>
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