<?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>spectrum</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="specsum.html" title="specsum" /> <link rel="next" href="splitrig.html" title="splitrig" /> </head> <body> <div class="navheader"> <table width="100%" summary="Navigation header"> <tr> <th colspan="3" align="center">spectrum</th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="specsum.html">Prev</a> </td> <th width="60%" align="center">Orchestra Opcodes and Operators</th> <td width="20%" align="right"> <a accesskey="n" href="splitrig.html">Next</a></td> </tr> </table> <hr /> </div> <div class="refentry"> <a id="spectrum"></a> <div class="titlepage"></div> <a id="IndexSpectrum" class="indexterm"></a> <div class="refnamediv"> <h2> <span class="refentrytitle">spectrum</span> </h2> <p>spectrum — Generate a constant-Q, exponentially-spaced DFT. </p> </div> <div class="refsect1"> <a id="idm281472886175224"></a> <h2>Description</h2> <p> Generate a constant-Q, exponentially-spaced DFT across all octaves of a multiply-downsampled control or audio input signal. </p> </div> <div class="refsect1"> <a id="idm281472886173896"></a> <h2>Syntax</h2> <pre class="synopsis">wsig <span class="command"><strong>spectrum</strong></span> xsig, iprd, iocts, ifrqa [, iq] [, ihann] [, idbout] \ [, idsprd] [, idsinrs]</pre> </div> <div class="refsect1"> <a id="idm281472886171720"></a> <h2>Initialization</h2> <p> <span class="emphasis"><em>ihann</em></span> (optional) -- apply a Hamming or Hanning window to the input. The default is 0 (Hamming window) </p> <p> <span class="emphasis"><em>idbout</em></span> (optional) -- coded conversion of the DFT output: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p>0 = magnitude</p> </li> <li class="listitem"> <p>1 = dB</p> </li> <li class="listitem"> <p>2 = mag squared</p> </li> <li class="listitem"> <p>3 = root magnitude</p> </li> </ul> </div> <p> The default value is 0 (magnitude). </p> <p> <span class="emphasis"><em>idisprd</em></span> (optional) -- if non-zero, display the composite downsampling buffer every <span class="emphasis"><em>idisprd</em></span> seconds. The default value is 0 (no display). </p> <p> <span class="emphasis"><em>idsines</em></span> (optional) -- if non-zero, display the Hamming or Hanning windowed sinusoids used in DFT filtering. The default value is 0 (no sinusoid display). </p> </div> <div class="refsect1"> <a id="idm281472886097416"></a> <h2>Performance</h2> <p> This unit first puts signal <span class="emphasis"><em>asig</em></span> or <span class="emphasis"><em>ksig</em></span> through <span class="emphasis"><em>iocts</em></span> of successive octave decimation and downsampling, and preserves a buffer of down-sampled values in each octave (optionally displayed as a composite buffer every <span class="emphasis"><em>idisprd</em></span> seconds). Then at every <span class="emphasis"><em>iprd</em></span> seconds, the preserved samples are passed through a filter bank (<span class="emphasis"><em>ifrqs</em></span> parallel filters per octave, exponentially spaced, with frequency/bandwidth Q of <span class="emphasis"><em>iq</em></span>), and the output magnitudes optionally converted (<span class="emphasis"><em>idbout </em></span>) to produce a band-limited spectrum that can be read by other units. </p> <p> The stages in this process are computationally intensive, and computation time varies directly with <span class="emphasis"><em>iocts</em></span>, <span class="emphasis"><em>ifrqs</em></span>, <span class="emphasis"><em>iq</em></span>, and inversely with <span class="emphasis"><em>iprd</em></span>. Settings of <span class="emphasis"><em>ifrqs</em></span> = 12, <span class="emphasis"><em>iq</em></span> = 10, <span class="emphasis"><em>idbout</em></span> = 3, and <span class="emphasis"><em>iprd</em></span> = .02 will normally be adequate, but experimentation is encouraged. <span class="emphasis"><em>ifrqs</em></span> currently has a maximum of 120 divisions per octave. For audio input, the frequency bins are tuned to coincide with A440. </p> <p> This unit produces a self-defining spectral datablock <span class="emphasis"><em>wsig</em></span>, whose characteristics used (<span class="emphasis"><em>iprd</em></span>, <span class="emphasis"><em>iocts</em></span>, <span class="emphasis"><em>ifrqs</em></span>, <span class="emphasis"><em>idbout</em></span>) are passed via the data block itself to all derivative <span class="emphasis"><em>wsigs</em></span>. There can be any number of <span class="emphasis"><em>spectrum</em></span> units in an instrument or orchestra, but all <span class="emphasis"><em>wsig</em></span> names must be unique. </p> </div> <div class="refsect1"> <a id="idm281472886083608"></a> <h2>Examples</h2> <p> </p> <div class="informalexample"> <pre class="programlisting"> asig <span class="opc">in</span> <span class="comment">; get external audio</span> wsig <span class="opc">spectrum</span> asig, 0.02, 6, 12, 33, 0, 1, 1 <span class="comment">; downsample in 6 octs & calc a 72 pt dft</span> <span class="comment">; (Q 33, dB out) every 20 msecs</span></pre> </div> <p> </p> </div> </div> <div class="navfooter"> <hr /> <table width="100%" summary="Navigation footer"> <tr> <td width="40%" align="left"><a accesskey="p" href="specsum.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="splitrig.html">Next</a></td> </tr> <tr> <td width="40%" align="left" valign="top">specsum </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> <td width="40%" align="right" valign="top"> splitrig</td> </tr> </table> </div> </body> </html>