<?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" type="text/css" href="csound.css" /> <link rel="stylesheet" type="text/css" href="syntax-highlighting.css" /> <meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /> <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"> <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"> <a id="idm281472929944200"></a> <h2>Description</h2> <p> Envelope follower unit generator. </p> </div> <div class="refsect1"> <a id="idm281472929942872"></a> <h2>Syntax</h2> <pre class="synopsis">ares <span class="command"><strong>follow</strong></span> asig, idt</pre> </div> <div class="refsect1"> <a id="idm281472929869592"></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"> <a id="idm281472929866136"></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"> <a id="idm281472929864360"></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="idm281472929861656"></a> <p class="title"> <strong>Example 338. Example of the follow 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="idm281472761119256"></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 follow.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">;envelope follower</span> a<span class="n">s</span> <span class="nb">soundin</span> <span class="s">"beats.wav"</span> a<span class="n">s</span> <span class="o">=</span> a<span class="n">s</span><span class="o">*</span><span class="mf">.7</span> <span class="c1">;reduce volume a bit</span> a<span class="n">t</span> <span class="nb">tone</span> a<span class="n">s</span><span class="p">,</span> <span class="mi">500</span> <span class="c1">;smooth estimated envelope</span> a<span class="n">f</span> <span class="nb">follow</span> a<span class="n">t</span><span class="p">,</span> <span class="nb">p4</span> a<span class="n">sin</span> <span class="nb">poscil3</span> <span class="mf">.5</span><span class="p">,</span> <span class="mi">440</span><span class="p">,</span> <span class="mi">1</span> <span class="c1">; "beats.wav" provides amplitude for poscil</span> a<span class="n">sig</span> <span class="nb">balance</span> a<span class="n">sin</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="c1">;sine wave.</span> <span class="nb">f</span> <span class="mi">1</span> <span class="mi">0</span> <span class="mi">32768</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">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="c1">;follow quickly</span> <span class="nb">i</span> <span class="mi">2</span> <span class="mi">5</span> <span class="mi">3</span> <span class="mf">0.2</span> <span class="c1">;follow slowly</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> <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"> <a id="idm281472929856744"></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>