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<h2>
<span class="refentrytitle">follow2</span>
</h2>
<p>follow2 —
Another controllable envelope extractor.
</p>
</div>
<div class="refsect1">
<a id="idm281472929883704"></a>
<h2>Description</h2>
<p>
A controllable envelope extractor using the algorithm attributed to Jean-Marc Jot.
</p>
</div>
<div class="refsect1">
<a id="idm281472929821464"></a>
<h2>Syntax</h2>
<pre class="synopsis">ares <span class="command"><strong>follow2</strong></span> asig, katt, krel</pre>
</div>
<div class="refsect1">
<a id="idm281472929819224"></a>
<h2>Performance</h2>
<p>
<span class="emphasis"><em>asig</em></span> -- the input signal whose envelope is followed
</p>
<p>
<span class="emphasis"><em>katt</em></span> -- the attack rate (60dB attack time in seconds)
</p>
<p>
<span class="emphasis"><em>krel</em></span> -- the decay rate (60dB decay time in seconds)
</p>
<p>
The output tracks the amplitude envelope of the input signal. The rate at which the output grows to follow the signal is controlled by the <span class="emphasis"><em>katt</em></span>, and the rate at which it decreases in response to a lower amplitude, is controlled by the <span class="emphasis"><em>krel</em></span>. This gives a smoother envelope than <span class="emphasis"><em>follow</em></span>.
</p>
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<div class="refsect1">
<a id="idm281472929813624"></a>
<h2>Examples</h2>
<p>
Here is an example of the follow2 opcode. It uses the file <a class="ulink" href="examples/follow2.csd" target="_top"><em class="citetitle">follow2.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="idm281472929811000"></a>
<p class="title">
<strong>Example 339. Example of the follow2 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="idm281472761096328"></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">;;;realtime audio out</span>
<span class="c1">;-iadc ;;;uncomment -iadc if realtime audio input is needed too</span>
<span class="c1">; For Non-realtime ouput leave only the line below:</span>
<span class="c1">; -o follow2.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">32</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>
<span class="kd">instr</span> <span class="nf">1</span>
a<span class="n">sig</span> <span class="nb">soundin</span> <span class="s">"beats.wav"</span>
<span class="nb">outs</span> a<span class="n">sig</span><span class="p">,</span> a<span class="n">sig</span>
<span class="kd">endin</span>
<span class="kd">instr</span> <span class="nf">2</span> <span class="c1">;using follow2</span>
a<span class="n">s</span> <span class="nb">soundin</span> <span class="s">"beats.wav"</span>
a<span class="n">f</span> <span class="nb">follow2</span> a<span class="n">s</span><span class="p">,</span> <span class="nb">p4</span><span class="p">,</span> <span class="nb">p5</span>
a<span class="n">r</span> <span class="nb">rand</span> <span class="mi">44100</span> <span class="c1">;noise</span>
<span class="c1">; "beats.wav" provides amplitude for noise</span>
a<span class="n">sig</span> <span class="nb">balance</span> a<span class="n">r</span><span class="p">,</span> a<span class="n">f</span>
<span class="nb">outs</span> a<span class="n">sig</span><span class="p">,</span> a<span class="n">sig</span>
<span class="kd">endin</span>
<span class="nt"></CsInstruments></span>
<span class="nt"><CsScore></span>
<span class="nb">i</span> <span class="mi">1</span> <span class="mi">0</span> <span class="mi">2</span>
<span class="nb">i</span> <span class="mi">2</span> <span class="mi">2</span> <span class="mi">2</span> <span class="mf">0.001</span> <span class="mf">0.01</span> <span class="c1">;quick attack & deacy</span>
<span class="nb">i</span> <span class="mi">2</span> <span class="mi">5</span> <span class="mi">2</span> <span class="mf">0.1</span> <span class="mf">0.5</span> <span class="c1">;slow attack & deacy </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="idm281472929806808"></a>
<h2>Credits</h2>
<p>
</p>
<table border="0" summary="Simple list" class="simplelist">
<tr>
<td>Author: John ffitch</td>
</tr>
<tr>
<td>The algorithm for the <span class="emphasis"><em>follow2</em></span> is attributed to Jean-Marc Jot.</td>
</tr>
<tr>
<td>University of Bath, Codemist Ltd.</td>
</tr>
<tr>
<td>Bath, UK</td>
</tr>
<tr>
<td>February 2000</td>
</tr>
</table>
<p>
</p>
<p>New in Csound version 4.03</p>
<p>Added notes by Rasmus Ekman on September 2002.</p>
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