<?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>svfilter</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="sumarray.html" title="sumarray" />
<link rel="next" href="syncgrain.html" title="syncgrain" />
</head>
<body>
<div class="navheader">
<table width="100%" summary="Navigation header">
<tr>
<th colspan="3" align="center">svfilter</th>
</tr>
<tr>
<td width="20%" align="left"><a accesskey="p" href="sumarray.html">Prev</a> </td>
<th width="60%" align="center">Orchestra Opcodes and Operators</th>
<td width="20%" align="right"> <a accesskey="n" href="syncgrain.html">Next</a></td>
</tr>
</table>
<hr />
</div>
<div class="refentry">
<a id="svfilter"></a>
<div class="titlepage"></div>
<a id="IndexSvfilter" class="indexterm"></a>
<div class="refnamediv">
<h2>
<span class="refentrytitle">svfilter</span>
</h2>
<p>svfilter —
A resonant second order filter, with simultaneous lowpass, highpass and bandpass outputs.
</p>
</div>
<div class="refsect1">
<a id="idm281472882739048"></a>
<h2>Description</h2>
<p>
Implementation of a resonant second order filter, with simultaneous lowpass, highpass and bandpass outputs.
</p>
</div>
<div class="refsect1">
<a id="idm281472882737736"></a>
<h2>Syntax</h2>
<pre class="synopsis">alow, ahigh, aband <span class="command"><strong>svfilter</strong></span> asig, kcf, kq [, iscl] [, iskip]</pre>
</div>
<div class="refsect1">
<a id="idm281472882674760"></a>
<h2>Initialization</h2>
<p>
<span class="emphasis"><em>iscl</em></span> -- coded scaling factor, similar to
that in <a class="link" href="reson.html" title="reson"><em class="citetitle">reson</em></a>. A non-zero
value signifies a peak response factor of 1, i.e. all
frequencies other than <span class="emphasis"><em>kcf</em></span> are attenuated
in accordance with the (normalized) response curve. A zero value
signifies no scaling of the signal, leaving that to some later
adjustment (see <a class="link" href="balance.html" title="balance"><em class="citetitle">balance</em></a>). The
default value is 0.
</p>
<p>
<span class="emphasis"><em>iskip</em></span> (optional, default=0) -- 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="idm281472882669288"></a>
<h2>Performance</h2>
<p>
<span class="emphasis"><em>svfilter</em></span> is a second order state-variable filter, with k-rate controls for cutoff frequency and Q. As Q is increased, a resonant peak forms around the cutoff frequency. <span class="emphasis"><em>svfilter</em></span> has simultaneous lowpass, highpass, and bandpass filter outputs; by mixing the outputs together, a variety of frequency responses can be generated. The state-variable filter, or "multimode" filter was a common feature in early analog synthesizers, due to the wide variety of sounds available from the interaction between cutoff, resonance, and output mix ratios. <span class="emphasis"><em>svfilter</em></span> is well suited to the emulation of "analog" sounds, as well as other applications where resonant filters are called for.
</p>
<p>
<span class="emphasis"><em>kcf</em></span> -- Cutoff or resonant frequency of the filter, measured in Hz.
</p>
<p>
<span class="emphasis"><em>kq</em></span> -- Q of the filter, which is defined (for bandpass filters) as bandwidth/cutoff. <span class="emphasis"><em>kq</em></span> should be in a range between 1 and 500. As <span class="emphasis"><em>kq</em></span> is increased, the resonance of the filter increases, which corresponds to an increase in the magnitude and "sharpness" of the resonant peak. When using <span class="emphasis"><em>svfilter</em></span> without any scaling of the signal (where <span class="emphasis"><em>iscl</em></span> is either absent or 0), the volume of the resonant peak increases as Q increases. For high values of Q, it is recommended that <span class="emphasis"><em>iscl</em></span> be set to a non-zero value, or that an external scaling function such as <a class="link" href="balance.html" title="balance"><em class="citetitle">balance</em></a> is used.
</p>
<p>
<span class="emphasis"><em>svfilter</em></span> is based upon an algorithm in Hal Chamberlin's <span class="emphasis"><em>Musical Applications of Microprocessor</em></span>s (Hayden Books, 1985).
</p>
</div>
<div class="refsect1">
<a id="idm281472882658968"></a>
<h2>Examples</h2>
<p>
Here is an example of the svfilter opcode. It uses the file <a class="ulink" href="examples/svfilter.csd" target="_top"><em class="citetitle">svfilter.csd</em></a>.
</p>
<div class="example">
<a id="idm281472882657112"></a>
<p class="title">
<strong>Example 966. Example of the svfilter 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="idm281472704106920"></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>
<span class="c1">; Audio out Audio in No messages</span>
-odac -iadc -d <span class="c1">;;;RT audio I/O</span>
<span class="c1">; For Non-realtime ouput leave only the line below:</span>
<span class="c1">; -o svfilter.wav -W ;;; for file output any platform</span>
<span class="nt"></CsOptions></span>
<span class="nt"><CsInstruments></span>
<span class="c1">; Orchestra file for resonant filter sweep of a sawtooth-like waveform. </span>
<span class="c1">; The seperate outputs of the filter are scaled by values from the score,</span>
<span class="c1">; and are mixed together.</span>
<span class="vg">sr</span> <span class="o">=</span> <span class="mi">44100</span>
<span class="vg">kr</span> <span class="o">=</span> <span class="mi">2205</span>
<span class="vg">ksmps</span> <span class="o">=</span> <span class="mi">20</span>
<span class="vg">nchnls</span> <span class="o">=</span> <span class="mi">1</span>
<span class="kd">instr</span> <span class="nf">1</span>
i<span class="n">dur</span> <span class="o">=</span> <span class="nb">p3</span>
i<span class="n">freq</span> <span class="o">=</span> <span class="nb">p4</span>
i<span class="n">amp</span> <span class="o">=</span> <span class="nb">p5</span>
i<span class="n">lowamp</span> <span class="o">=</span> <span class="nb">p6</span> <span class="c1">; determines amount of lowpass output in signal</span>
i<span class="n">highamp</span> <span class="o">=</span> <span class="nb">p7</span> <span class="c1">; determines amount of highpass output in signal</span>
i<span class="n">bandamp</span> <span class="o">=</span> <span class="nb">p8</span> <span class="c1">; determines amount of bandpass output in signal</span>
i<span class="n">q</span> <span class="o">=</span> <span class="nb">p9</span> <span class="c1">; value of q</span>
i<span class="n">harms</span> <span class="o">=</span> <span class="p">(</span><span class="vg">sr</span><span class="o">*</span><span class="mf">.4</span><span class="p">)</span> <span class="o">/</span> i<span class="n">freq</span>
a<span class="n">sig</span> <span class="nb">gbuzz</span> <span class="mi">1</span><span class="p">,</span> i<span class="n">freq</span><span class="p">,</span> i<span class="n">harms</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mf">.9</span><span class="p">,</span> <span class="mi">1</span> <span class="c1">; Sawtooth-like waveform</span>
k<span class="n">freq</span> <span class="nb">linseg</span> <span class="mi">1</span><span class="p">,</span> i<span class="n">dur</span> <span class="o">*</span> <span class="mf">0.5</span><span class="p">,</span> <span class="mi">4000</span><span class="p">,</span> i<span class="n">dur</span> <span class="o">*</span> <span class="mf">0.5</span><span class="p">,</span> <span class="mi">1</span> <span class="c1">; Envelope to control filter cutoff</span>
a<span class="n">low</span><span class="p">,</span> a<span class="n">high</span><span class="p">,</span> a<span class="n">band</span> <span class="nb">svfilter</span> a<span class="n">sig</span><span class="p">,</span> k<span class="n">freq</span><span class="p">,</span> i<span class="n">q</span>
a<span class="n">out1</span> <span class="o">=</span> a<span class="n">low</span> <span class="o">*</span> i<span class="n">lowamp</span>
a<span class="n">out2</span> <span class="o">=</span> a<span class="n">high</span> <span class="o">*</span> i<span class="n">highamp</span>
a<span class="n">out3</span> <span class="o">=</span> a<span class="n">band</span> <span class="o">*</span> i<span class="n">bandamp</span>
a<span class="n">sum</span> <span class="o">=</span> a<span class="n">out1</span> <span class="o">+</span> a<span class="n">out2</span> <span class="o">+</span> a<span class="n">out3</span>
k<span class="n">env</span> <span class="nb">linseg</span> <span class="mi">0</span><span class="p">,</span> <span class="mf">.1</span><span class="p">,</span> i<span class="n">amp</span><span class="p">,</span> i<span class="n">dur</span> <span class="o">-</span><span class="mf">.2</span><span class="p">,</span> i<span class="n">amp</span><span class="p">,</span> <span class="mf">.1</span><span class="p">,</span> <span class="mi">0</span> <span class="c1">; Simple amplitude envelope</span>
<span class="nb">out</span> a<span class="n">sum</span> <span class="o">*</span> k<span class="n">env</span>
<span class="kd">endin</span>
<span class="nt"></CsInstruments></span>
<span class="nt"><CsScore></span>
<span class="nb">f</span><span class="mi">1</span> <span class="mi">0</span> <span class="mi">8192</span> <span class="mi">9</span> <span class="mi">1</span> <span class="mi">1</span> <span class="mf">.25</span>
<span class="nb">i</span><span class="mi">1</span> <span class="mi">0</span> <span class="mi">5</span> <span class="mi">100</span> <span class="mi">1000</span> <span class="mi">1</span> <span class="mi">0</span> <span class="mi">0</span> <span class="mi">5</span> <span class="c1">; lowpass sweep</span>
<span class="nb">i</span><span class="mi">1</span> <span class="mi">5</span> <span class="mi">5</span> <span class="mi">200</span> <span class="mi">1000</span> <span class="mi">1</span> <span class="mi">0</span> <span class="mi">0</span> <span class="mi">30</span> <span class="c1">; lowpass sweep, octave higher, higher q</span>
<span class="nb">i</span><span class="mi">1</span> <span class="mi">10</span> <span class="mi">5</span> <span class="mi">100</span> <span class="mi">1000</span> <span class="mi">0</span> <span class="mi">1</span> <span class="mi">0</span> <span class="mi">5</span> <span class="c1">; highpass sweep</span>
<span class="nb">i</span><span class="mi">1</span> <span class="mi">15</span> <span class="mi">5</span> <span class="mi">200</span> <span class="mi">1000</span> <span class="mi">0</span> <span class="mi">1</span> <span class="mi">0</span> <span class="mi">30</span> <span class="c1">; highpass sweep, octave higher, higher q</span>
<span class="nb">i</span><span class="mi">1</span> <span class="mi">20</span> <span class="mi">5</span> <span class="mi">100</span> <span class="mi">1000</span> <span class="mi">0</span> <span class="mi">0</span> <span class="mi">1</span> <span class="mi">5</span> <span class="c1">; bandpass sweep</span>
<span class="nb">i</span><span class="mi">1</span> <span class="mi">25</span> <span class="mi">5</span> <span class="mi">200</span> <span class="mi">1000</span> <span class="mi">0</span> <span class="mi">0</span> <span class="mi">1</span> <span class="mi">30</span> <span class="c1">; bandpass sweep, octave higher, higher q</span>
<span class="nb">i</span><span class="mi">1</span> <span class="mi">30</span> <span class="mi">5</span> <span class="mi">200</span> <span class="mi">2000</span> <span class="mf">.4</span> <span class="mf">.6</span> <span class="mi">0</span> <span class="c1">; notch sweep - notch formed by combining highpass and lowpass outputs</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="idm281472882652824"></a>
<h2>Credits</h2>
<p>
</p>
<table border="0" summary="Simple list" class="simplelist">
<tr>
<td>Author: Sean Costello</td>
</tr>
<tr>
<td>Seattle, Washington</td>
</tr>
<tr>
<td>1999</td>
</tr>
</table>
<p>
</p>
<p>New in Csound version 3.55</p>
<p>iskip new in version 6.06</p>
</div>
</div>
<div class="navfooter">
<hr />
<table width="100%" summary="Navigation footer">
<tr>
<td width="40%" align="left"><a accesskey="p" href="sumarray.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="syncgrain.html">Next</a></td>
</tr>
<tr>
<td width="40%" align="left" valign="top">sumarray </td>
<td width="20%" align="center">
<a accesskey="h" href="index.html">Home</a>
</td>
<td width="40%" align="right" valign="top"> syncgrain</td>
</tr>
</table>
</div>
</body>
</html>
distrib
>
Mageia
>
7
>
armv7hl
>
media
>
core-release
>
by-pkgid
>
5fcfcb7517038d1f44ab4e478e6e61fa
>
files
>
2996
