<?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>eqfil</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="ephasor.html" title="ephasor" /> <link rel="next" href="evalstr.html" title="evalstr" /> </head> <body> <div class="navheader"> <table width="100%" summary="Navigation header"> <tr> <th colspan="3" align="center">eqfil</th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="ephasor.html">Prev</a> </td> <th width="60%" align="center">Orchestra Opcodes and Operators</th> <td width="20%" align="right"> <a accesskey="n" href="evalstr.html">Next</a></td> </tr> </table> <hr /> </div> <div class="refentry"> <a id="eqfil"></a> <div class="titlepage"></div> <a id="Indexeqfil" class="indexterm"></a> <div class="refnamediv"> <h2> <span class="refentrytitle">eqfil</span> </h2> <p>eqfil — Equalizer filter </p> </div> <div class="refsect1"> <a id="idm281472939416584"></a> <h2>Description</h2> <p> The opcode eqfil is a 2nd order tunable equalisation filter based on Regalia and Mitra design ("Tunable Digital Frequency Response Equalization Filters", IEEE Trans. on Ac., Sp. and Sig Proc., 35 (1), 1987). It provides a peak/notch filter for building parametric/graphic equalisers. </p> <p> The amplitude response for this filter will be flat (=1) for <span class="emphasis"><em>kgain</em></span>=1. With <span class="emphasis"><em>kgain</em></span> bigger than 1, there will be a peak at the centre frequency, whose width is given by the <span class="emphasis"><em>kbw</em></span> parameter, but outside this band, the response will tend towards 1. Conversely, if <span class="emphasis"><em>kgain</em></span> is smaller than 1, a notch will be created around the CF. </p> </div> <div class="refsect1"> <a id="idm281472939402552"></a> <h2>Syntax</h2> <pre class="synopsis">asig <span class="command"><strong>eqfil</strong></span> ain, kcf, kbw, kgain[, istor]</pre> </div> <div class="refsect1"> <a id="idm281472939400328"></a> <h2>Initialization</h2> <p> <span class="emphasis"><em>istor</em></span> --initial disposition of internal data space. Since filtering incorporates a feedback loop of previous output, the initial status of the storage space used is significant. A zero value will clear the space; a non-zero value will allow previous information to remain. The default value is 0. </p> </div> <div class="refsect1"> <a id="idm281472939345224"></a> <h2>Performance</h2> <p> <span class="emphasis"><em>asig</em></span> -- filtered output signal. </p> <p> <span class="emphasis"><em>ain</em></span> -- input signal. </p> <p> <span class="emphasis"><em>kcf</em></span> -- filter centre frequency. </p> <p> <span class="emphasis"><em>kbw</em></span> -- peak/notch bandwidth (Hz). </p> <p> <span class="emphasis"><em>kgain</em></span> -- peak/notch gain. </p> </div> <div class="refsect1"> <a id="idm281472939340616"></a> <h2>Examples</h2> <p> Here is an example of the eqfil opcode. It uses the file <a class="ulink" href="examples/eqfil.csd" target="_top"><em class="citetitle">eqfil.csd</em></a>. </p> <div class="example"> <a id="idm281472939338968"></a> <p class="title"> <strong>Example 245. Example of the eqfil 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="idm281472771587304"></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 eqfil.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> k<span class="n">cf</span> <span class="o">=</span> <span class="nb">p4</span> k<span class="n">fe</span> <span class="nb">expseg</span> <span class="mi">10</span><span class="p">,</span> <span class="nb">p3</span><span class="o">*</span><span class="mf">0.9</span><span class="p">,</span> <span class="mi">1800</span><span class="p">,</span> <span class="nb">p3</span><span class="o">*</span><span class="mf">0.1</span><span class="p">,</span> <span class="mi">175</span> k<span class="n">env</span> <span class="nb">linen</span> <span class="mf">.03</span><span class="p">,</span> <span class="mf">0.05</span><span class="p">,</span> <span class="nb">p3</span><span class="p">,</span> <span class="mf">0.05</span> <span class="c1">;low amplitude is needed to avoid clipping</span> a<span class="n">sig</span> <span class="nb">buzz</span> k<span class="n">env</span><span class="p">,</span> k<span class="n">fe</span><span class="p">,</span> <span class="vg">sr</span><span class="o">/</span><span class="p">(</span><span class="mi">2</span><span class="o">*</span>k<span class="n">fe</span><span class="p">),</span> <span class="mi">1</span> a<span class="n">fil</span> <span class="nb">eqfil</span> a<span class="n">sig</span><span class="p">,</span> k<span class="n">cf</span><span class="p">,</span> <span class="mi">200</span><span class="p">,</span> <span class="mi">10</span> <span class="nb">outs</span> a<span class="n">fil</span><span class="o">*</span><span class="mi">20</span><span class="p">,</span> a<span class="n">fil</span><span class="o">*</span><span class="mi">20</span> <span class="kd">endin</span> <span class="nt"></CsInstruments></span> <span class="nt"><CsScore></span> <span class="c1">; a sine wave.</span> <span class="nb">f</span> <span class="mi">1</span> <span class="mi">0</span> <span class="mi">16384</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">10</span> <span class="mi">200</span> <span class="c1">;filter centre freq=200</span> <span class="nb">i</span> <span class="mi">1</span> <span class="o">+</span> <span class="mi">10</span> <span class="mi">1500</span> <span class="c1">;filter centre freq=1500</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="idm281472939335560"></a> <h2>Credits</h2> <p> </p> <table border="0" summary="Simple list" class="simplelist"> <tr> <td>Author: Victor Lazzarini</td> </tr> <tr> <td>April 2007</td> </tr> </table> <p> </p> <p>New in version 5.06</p> </div> </div> <div class="navfooter"> <hr /> <table width="100%" summary="Navigation footer"> <tr> <td width="40%" align="left"><a accesskey="p" href="ephasor.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="evalstr.html">Next</a></td> </tr> <tr> <td width="40%" align="left" valign="top">ephasor </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> <td width="40%" align="right" valign="top"> evalstr</td> </tr> </table> </div> </body> </html>