<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>follow</title>
<link rel="stylesheet" href="csound.css" type="text/css" />
<meta name="generator" content="DocBook XSL Stylesheets V1.75.2" />
<link rel="home" href="index.html" title="The Canonical Csound Reference Manual" />
<link rel="up" href="OpcodesTop.html" title="Orchestra Opcodes and Operators" />
<link rel="prev" href="fold.html" title="fold" />
<link rel="next" href="follow2.html" title="follow2" />
</head>
<body>
<div class="navheader">
<table width="100%" summary="Navigation header">
<tr>
<th colspan="3" align="center">follow</th>
</tr>
<tr>
<td width="20%" align="left"><a accesskey="p" href="fold.html">Prev</a> </td>
<th width="60%" align="center">Orchestra Opcodes and Operators</th>
<td width="20%" align="right"> <a accesskey="n" href="follow2.html">Next</a></td>
</tr>
</table>
<hr />
</div>
<div class="refentry" title="follow">
<a id="follow"></a>
<div class="titlepage"></div>
<a id="IndexFollow" class="indexterm"></a>
<div class="refnamediv">
<h2>
<span class="refentrytitle">follow</span>
</h2>
<p>follow —
Envelope follower unit generator.
</p>
</div>
<div class="refsect1" title="Description">
<a id="id2913617"></a>
<h2>Description</h2>
<p>
Envelope follower unit generator.
</p>
</div>
<div class="refsect1" title="Syntax">
<a id="id2913245"></a>
<h2>Syntax</h2>
<pre class="synopsis">ares <span class="command"><strong>follow</strong></span> asig, idt</pre>
</div>
<div class="refsect1" title="Initialization">
<a id="id2913264"></a>
<h2>Initialization</h2>
<p>
<span class="emphasis"><em>idt</em></span> -- This is the period, in seconds, that the average amplitude of <span class="emphasis"><em>asig</em></span> is reported. If the frequency of <span class="emphasis"><em>asig</em></span> is low then <span class="emphasis"><em>idt</em></span> must be large (more than half the period of <span class="emphasis"><em>asig</em></span> )
</p>
</div>
<div class="refsect1" title="Performance">
<a id="id2914020"></a>
<h2>Performance</h2>
<p>
<span class="emphasis"><em>asig</em></span> -- This is the signal from which to extract the envelope.
</p>
</div>
<div class="refsect1" title="Examples">
<a id="id2914036"></a>
<h2>Examples</h2>
<p>
Here is an example of the follow opcode. It uses the file <a class="ulink" href="examples/follow.csd" target="_top"><em class="citetitle">follow.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="id2914059"></a>
<p class="title">
<b>Example 258. Example of the follow opcode.</b>
</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 <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 follow.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">kr</span> <span class="op">=</span> 4410
<span class="ohdr">ksmps</span> <span class="op">=</span> 10
<span class="ohdr">nchnls</span> <span class="op">=</span> 1
<span class="comment">; Instrument #1 - play a WAV file.</span>
<span class="oblock">instr</span> 1
a1 <span class="opc">soundin</span> "beats.wav"
<span class="opc">out</span> a1
<span class="oblock">endin</span>
<span class="comment">; Instrument #2 - have another waveform follow the WAV file.</span>
<span class="oblock">instr</span> 2
<span class="comment">; Follow the WAV file.</span>
as <span class="opc">soundin</span> "beats.wav"
af <span class="opc">follow</span> as, 0.01
<span class="comment">; Use a sine waveform.</span>
as <span class="opc">oscil</span> 4000, 440, 1
<span class="comment">; Have it use the amplitude of the followed WAV file.</span>
a1 <span class="opc">balance</span> as, af
<span class="opc">out</span> a1
<span class="oblock">endin</span>
<span class="csdtag"></CsInstruments></span>
<span class="csdtag"><CsScore></span>
<span class="comment">; Just generate a nice, ordinary sine wave.</span>
<span class="stamnt">f</span> 1 0 32768 10 1
<span class="comment">; Play Instrument #1 for two seconds.</span>
<span class="stamnt">i</span> 1 0 2
<span class="comment">; Play Instrument #2 for two seconds.</span>
<span class="stamnt">i</span> 2 2 2
<span class="stamnt">e</span>
<span class="csdtag"></CsScore></span>
<span class="csdtag"></CsoundSynthesizer></span>
</pre>
</div>
</div>
<p><br class="example-break" />
</p>
<p>
To avoid zipper noise, by discontinuities produced from complex envelope tracking, a lowpass filter could be used, to smooth the estimated envelope.
</p>
</div>
<div class="refsect1" title="Credits">
<a id="id2914106"></a>
<h2>Credits</h2>
<p>
</p>
<table border="0" summary="Simple list" class="simplelist">
<tr>
<td>Author: Paris Smaragdis</td>
</tr>
<tr>
<td>MIT, Cambridge</td>
</tr>
<tr>
<td>1995</td>
</tr>
</table>
<p>
</p>
</div>
</div>
<div class="navfooter">
<hr />
<table width="100%" summary="Navigation footer">
<tr>
<td width="40%" align="left"><a accesskey="p" href="fold.html">Prev</a> </td>
<td width="20%" align="center">
<a accesskey="u" href="OpcodesTop.html">Up</a>
</td>
<td width="40%" align="right"> <a accesskey="n" href="follow2.html">Next</a></td>
</tr>
<tr>
<td width="40%" align="left" valign="top">fold </td>
<td width="20%" align="center">
<a accesskey="h" href="index.html">Home</a>
</td>
<td width="40%" align="right" valign="top"> follow2</td>
</tr>
</table>
</div>
</body>
</html>
