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<div class="refentry" title="dam">
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<h2>
<span class="refentrytitle">dam</span>
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<p>dam —
A dynamic compressor/expander.
</p>
</div>
<div class="refsect1" title="Description">
<a id="idp17480976"></a>
<h2>Description</h2>
<p>
This opcode dynamically modifies a gain value applied to the input sound <span class="emphasis"><em>ain</em></span> by comparing its power level to a given threshold level. The signal will be compressed/expanded with different factors regarding that it is over or under the threshold.
</p>
</div>
<div class="refsect1" title="Syntax">
<a id="idp17481864"></a>
<h2>Syntax</h2>
<pre class="synopsis">ares <span class="command"><strong>dam</strong></span> asig, kthreshold, icomp1, icomp2, irtime, iftime</pre>
</div>
<div class="refsect1" title="Initialization">
<a id="idp17556440"></a>
<h2>Initialization</h2>
<p>
<span class="emphasis"><em>icomp1</em></span> -- compression ratio for upper zone.
</p>
<p>
<span class="emphasis"><em>icomp2</em></span> -- compression ratio for lower zone
</p>
<p>
<span class="emphasis"><em>irtime</em></span> -- gain rise time in seconds. Time over which the gain factor is allowed to raise of one unit.
</p>
<p>
<span class="emphasis"><em>iftime</em></span> -- gain fall time in seconds. Time over which the gain factor is allowed to decrease of one unit.
</p>
</div>
<div class="refsect1" title="Performance">
<a id="idp17559120"></a>
<h2>Performance</h2>
<p>
<span class="emphasis"><em>asig</em></span> -- input signal to be modified
</p>
<p>
<span class="emphasis"><em>kthreshold</em></span> -- level of input signal which acts as the threshold. Can be changed at k-time (e.g. for ducking)
</p>
<p>
Note on the compression factors: A compression ratio of one leaves the sound unchanged. Setting the ratio to a value smaller than one will compress the signal (reduce its volume) while setting the ratio to a value greater than one will expand the signal (augment its volume).
</p>
</div>
<div class="refsect1" title="Examples">
<a id="idp17561440"></a>
<h2>Examples</h2>
<p>
Because the results of the <span class="emphasis"><em>dam</em></span> opcode can be subtle, I recommend looking at them in a graphical audio editor program like <span class="emphasis"><em>audacity</em></span>. <span class="emphasis"><em>audacity</em></span> is available for Linux, Windows, and the MacOS and may be downloaded from <a class="ulink" href="http://audacity.sourceforge.net/" target="_top"><em class="citetitle">http://audacity.sourceforge.net</em></a>.
</p>
<p>
Here is an example of the dam opcode. It uses the file <a class="ulink" href="examples/dam.csd" target="_top"><em class="citetitle">dam.csd</em></a>, and <a class="ulink" href="examples/beats.wav" target="_top"><em class="citetitle">beats.wav</em></a>.
</p>
<div class="example">
<a id="idp17564368"></a>
<p class="title">
<strong>Example 149. An example of the dam opcode compressing an audio signal.</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 dam.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
<span class="oblock">instr</span> 1 <span class="comment">;normal audio</span>
asig <span class="opc">diskin2</span> "beats.wav", 1, 0, 1
<span class="opc">outs</span> asig, asig
<span class="oblock">endin</span>
<span class="oblock">instr</span> 2 <span class="comment">; compressed audio</span>
kthreshold <span class="op">=</span> 0.2
icomp1 <span class="op">=</span> 0.8
icomp2 <span class="op">=</span> 0.2
irtime <span class="op">=</span> 0.01
iftime <span class="op">=</span> 0.5
asig <span class="opc">diskin2</span> "beats.wav", 1, 0, 1
asig <span class="opc">dam</span> asig, kthreshold, icomp1, icomp2, irtime, iftime
<span class="opc">outs</span> asig, asig
<span class="oblock">endin</span>
<span class="csdtag"></CsInstruments></span>
<span class="csdtag"><CsScore></span>
<span class="stamnt">i</span> 1 0 2
<span class="stamnt">i</span> 2 2.5 8.5
<span class="stamnt">e</span>
<span class="csdtag"></CsScore></span>
<span class="csdtag"></CsoundSynthesizer></span>
</pre>
</div>
</div>
<p><br class="example-break" />
This example compresses the audio file <span class="quote">“<span class="quote">beats.wav</span>”</span>. You should hear a drum pattern repeat twice. The second time, the sound should be quieter (compressed) than the first.
</p>
<p>
Here is another example of the dam opcode. It uses the file <a class="ulink" href="examples/dam_expanded.csd" target="_top"><em class="citetitle">dam_expanded.csd</em></a>, and <a class="ulink" href="examples/beats.wav" target="_top"><em class="citetitle">beats.wav</em></a>.
</p>
<div class="example">
<a id="idp17568144"></a>
<p class="title">
<strong>Example 150. An example of the dam opcode expanding an audio signal.</strong>
</p>
<div class="example-contents">
<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 dam_expanded.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
<span class="oblock">instr</span> 1
asig <span class="opc">diskin2</span> "beats.wav", 1, 0, 1
<span class="opc">outs</span> asig, asig
<span class="oblock">endin</span>
<span class="oblock">instr</span> 2 <span class="comment">;expanded audio</span>
kthreshold <span class="op">=</span> .5
icomp1 <span class="op">=</span> 2
icomp2 <span class="op">=</span> 3
irtime <span class="op">=</span> 0.01
iftime <span class="op">=</span> 0.1
asig <span class="opc">diskin2</span> "beats.wav", 1, 0, 1
asig <span class="opc">dam</span> asig, kthreshold, icomp1, icomp2, irtime, iftime
<span class="opc">outs</span> asig<span class="op">*</span>.2, asig<span class="op">*</span>.2 <span class="comment">;adjust volume of expanded beat</span>
<span class="oblock">endin</span>
<span class="csdtag"></CsInstruments></span>
<span class="csdtag"><CsScore></span>
<span class="stamnt">i</span> 1 0 2
<span class="stamnt">i</span> 2 2.5 6.5
<span class="stamnt">e</span>
<span class="csdtag"></CsScore></span>
<span class="csdtag"></CsoundSynthesizer></span>
</pre>
</div>
</div>
<p><br class="example-break" />
This example expands the audio file <span class="quote">“<span class="quote">beats.wav</span>”</span>. You should hear a drum pattern repeat twice. The second time, the sound should be louder (expanded) than the first. To prevent distortion the volume of the signal has been lowered.
</p>
</div>
<div class="refsect1" title="See Also">
<a id="idp17569856"></a>
<h2>See Also</h2>
<p>
<a class="link" href="compress.html" title="compress"><em class="citetitle">compress</em></a>
</p>
</div>
<div class="refsect1" title="Credits">
<a id="idp17570912"></a>
<h2>Credits</h2>
<p>
</p>
<table border="0" summary="Simple list" class="simplelist">
<tr>
<td>Author: Marc Resibois</td>
</tr>
<tr>
<td>Belgium</td>
</tr>
<tr>
<td>1997</td>
</tr>
</table>
<p>
</p>
<p>New in version 3.47</p>
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