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<div class="refentry" title="rms">
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<h2>
<span class="refentrytitle">rms</span>
</h2>
<p>rms —
Determines the root-mean-square amplitude of an audio signal.
</p>
</div>
<div class="refsect1" title="Description">
<a id="idp40968632"></a>
<h2>Description</h2>
<p>
Determines the root-mean-square amplitude of an audio signal. It low-pass filters the actual value, to average in the manner of a VU meter.
</p>
</div>
<div class="refsect1" title="Syntax">
<a id="idp40946168"></a>
<h2>Syntax</h2>
<pre class="synopsis">kres <span class="command"><strong>rms</strong></span> asig [, ihp] [, iskip]</pre>
</div>
<div class="refsect1" title="Initialization">
<a id="idp40947224"></a>
<h2>Initialization</h2>
<p>
<span class="emphasis"><em>ihp</em></span> (optional, default=10) -- half-power point (in Hz) of a special internal low-pass filter. The default value is 10.
</p>
<p>
<span class="emphasis"><em>iskip</em></span> (optional, default=0) -- initial disposition of internal data space (see <a class="link" href="reson.html" title="reson"><em class="citetitle">reson</em></a>). The default value is 0.
</p>
</div>
<div class="refsect1" title="Performance">
<a id="idp40991432"></a>
<h2>Performance</h2>
<p>
<span class="emphasis"><em>asig</em></span> -- input audio signal
</p>
<p>
<span class="emphasis"><em>kres</em></span> -- low-pass filtered rms value of the input signal
</p>
<p>
<span class="emphasis"><em>rms</em></span> output values <span class="emphasis"><em>kres</em></span> will trace the root-mean-square value of the audio input <span class="emphasis"><em>asig</em></span>. This unit is not a signal modifier, but functions rather as a signal power-gauge. It uses an internal low-pass filter to make the response smoother. <span class="emphasis"><em>ihp</em></span> can be used to control this smoothing. The higher the value, the "snappier" the measurement.
</p>
<p>
This opcode can also be used as an evelope follower.
</p>
<p>
The <span class="emphasis"><em>kres</em></span> output from this opcode is given in amplitude and depends on <a class="link" href="Zerodbfs.html" title="0dbfs"><em class="citetitle">0dbfs</em></a>. If you want the output in decibels, you can use <a class="link" href="dbamp.html" title="dbamp"><em class="citetitle">dbamp</em></a>
</p>
</div>
<div class="refsect1" title="Examples">
<a id="idp40995792"></a>
<h2>Examples</h2>
<p>
</p>
<div class="informalexample">
<pre class="programlisting">
arms <span class="opc">rms</span> asig <span class="comment">; get rms value of signal asig</span>
</pre>
</div>
<p>
</p>
<p>
Here is an example of the rms opcode. It uses the file <a class="ulink" href="examples/rms.csd" target="_top"><em class="citetitle">rms.csd</em></a>.
</p>
<div class="example">
<a id="idp40998192"></a>
<p class="title">
<strong>Example 726. Example of the rms 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>
<span class="comment">; Audio out Audio in No messages</span>
-odac -iadc -d -m0 <span class="comment">;;;RT audio I/O</span>
<span class="comment">; For Non-realtime ouput leave only the line below:</span>
<span class="comment">; -o rms.wav -W ;;; for file output any platform</span>
<span class="csdtag"></CsOptions></span>
<span class="csdtag"><CsInstruments></span>
<span class="comment">; Initialize the global variables.</span>
<span class="ohdr">sr</span> <span class="op">=</span> 44100
<span class="ohdr">ksmps</span> <span class="op">=</span> 128
<span class="ohdr">nchnls</span> <span class="op">=</span> 1
<span class="comment">;Example by Andres Cabrera 2007</span>
<span class="ohdr">0dbfs</span> <span class="op">=</span> 1
<span class="opc">FLpanel</span> "rms", 400, 100, 50, 50
gkrmstext, gihrmstext <span class="opc">FLtext</span> "Rms", <span class="op">-</span>100, 0, 0.1, 3, 110, 30, 60, 50
gkihp, gihandle <span class="opc">FLtext</span> "ihp", 0, 10, 0.05, 1, 100, 30, 220, 50
gkrmsslider, gihrmsslider <span class="opc">FLslider</span> "", <span class="op">-</span>60, <span class="op">-</span>0.5, <span class="op">-</span>1, 5, <span class="op">-</span>1, 380, 20, 10, 10
<span class="opc">FLpanelEnd</span>
<span class="opc">FLrun</span>
<span class="opc">FLsetVal_i</span> 5, gihandle
<span class="comment">; Instrument #1.</span>
<span class="oblock">instr</span> 1
a1 <span class="opc">inch</span> 1
<span class="olabel">label</span><span class="op">:</span>
kval <span class="opc">rms</span> a1, <span class="opc">i</span>(gkihp) <span class="comment">;measures rms of input channel 1</span>
<span class="opc">rireturn</span>
kval <span class="op">=</span> <span class="opc">dbamp</span>(kval) <span class="comment">; convert to db full scale</span>
<span class="opc">printk</span> 0.5, kval
<span class="opc">FLsetVal</span> 1, kval, gihrmsslider <span class="comment">;update the slider and text values</span>
<span class="opc">FLsetVal</span> 1, kval, gihrmstext
knewihp <span class="opc">changed</span> gkihp <span class="comment">; reinit when ihp text has changed</span>
<span class="octrl">if</span> (knewihp <span class="op">==</span> 1) then
<span class="opc">reinit</span> <span class="olabel">label</span> <span class="comment">;needed because ihp is an i-rate parameter</span>
<span class="octrl">endif</span>
<span class="oblock">endin</span>
<span class="csdtag"></CsInstruments></span>
<span class="csdtag"><CsScore></span>
<span class="comment">; Play Instrument #1 for one minute</span>
<span class="stamnt">i</span> 1 0 60
<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="idp41000456"></a>
<h2>See Also</h2>
<p>
<a class="link" href="balance.html" title="balance"><em class="citetitle">balance</em></a>,
<a class="link" href="gain.html" title="gain"><em class="citetitle">gain</em></a>
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