<?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>rfft</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="rezzy.html" title="rezzy" /> <link rel="next" href="rifft.html" title="rifft" /> </head> <body> <div class="navheader"> <table width="100%" summary="Navigation header"> <tr> <th colspan="3" align="center">rfft</th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="rezzy.html">Prev</a> </td> <th width="60%" align="center">Orchestra Opcodes and Operators</th> <td width="20%" align="right"> <a accesskey="n" href="rifft.html">Next</a></td> </tr> </table> <hr /> </div> <div class="refentry"> <a id="rfft"></a> <div class="titlepage"></div> <a id="IndexRfft" class="indexterm"></a> <div class="refnamediv"> <h2> <span class="refentrytitle">rfft</span> </h2> <p>rfft — Fast Fourier Transform of a real-value array. </p> </div> <div class="refsect1"> <a id="idm281472894642776"></a> <h2>Description</h2> <p> Applies a forward Fast Fourier Transform to a real-value input 1-dimensional array. The output is another array containing the transform, non-redundant, non-negative spectrum only. If the input array is power-of-two, the output array size will match the input size, with the first two points containing 0Hz and Nyquist frequency coefficients. Otherwise, the output will have two extra values (input size + 2), and the the Nyquist coefficient will be placed at kin[input_size] position (kin[1] and kin[input_size+1] will be 0]. </p> </div> <div class="refsect1"> <a id="idm281472894638744"></a> <h2>Syntax</h2> <pre class="synopsis">kout[] <span class="command"><strong>rfft</strong></span> kin[]</pre> </div> <div class="refsect1"> <a id="idm281472894636536"></a> <h2>Performance</h2> <p> <span class="emphasis"><em>kout[]</em></span> -- output array containing the transform. It will be created if it does not exist. </p> <p> <span class="emphasis"><em>kin[]</em></span> -- input array containing the real-valued input. </p> </div> <div class="refsect1"> <a id="idm281472894576904"></a> <h2>Examples</h2> <p> Here is an example of the rfft opcode. It uses the file <a class="ulink" href="examples/rfft.csd" target="_top"><em class="citetitle">rfft.csd</em></a>.</p> <div class="example"> <a id="idm281472894574984"></a> <p class="title"> <strong>Example 835. Example of the rfft 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="idm281472715519160"></a> <pre class="programlisting"> <span class="nt"><CsoundSynthesizer></span> <span class="nt"><CsOptions></span> -d -o dac <span class="nt"></CsOptions></span> <span class="nt"><CsInstruments></span> <span class="c1">;ksmps needs to be an integer div of hopsize</span> <span class="vg">ksmps</span> <span class="o">=</span> <span class="mi">64</span> <span class="kd">instr</span> <span class="nf">1</span> i<span class="n">hopsize</span> <span class="o">=</span> <span class="mi">256</span> <span class="c1">; hopsize</span> i<span class="n">fftsize</span> <span class="o">=</span> <span class="mi">1024</span> <span class="c1">; FFT size</span> i<span class="n">olaps</span> <span class="o">=</span> i<span class="n">fftsize</span><span class="o">/</span>i<span class="n">hopsize</span> <span class="c1">; overlaps</span> i<span class="n">bw</span> <span class="o">=</span> <span class="vg">sr</span><span class="o">/</span>i<span class="n">fftsize</span> <span class="c1">; bin bandwidth</span> k<span class="n">cnt</span> <span class="nb">init</span> <span class="mi">0</span> <span class="c1">; counting vars</span> k<span class="n">row</span> <span class="nb">init</span> <span class="mi">0</span> k<span class="n">Ola</span><span class="p">[]</span> <span class="nb">init</span> i<span class="n">fftsize</span> <span class="c1">; overlap-add buffer</span> k<span class="n">In</span><span class="p">[]</span> <span class="nb">init</span> i<span class="n">fftsize</span> <span class="c1">; input buffer</span> k<span class="n">Sw</span><span class="p">[]</span> <span class="nb">init</span> i<span class="n">fftsize</span> k<span class="n">Out</span><span class="p">[][]</span> <span class="nb">init</span> i<span class="n">olaps</span><span class="p">,</span> i<span class="n">fftsize</span> <span class="c1">; output buffers</span> a<span class="n">1</span> <span class="nb">diskin2</span> <span class="s">"fox.wav"</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span> <span class="c1">; audio input</span> k<span class="n">s</span> <span class="nb">expon</span> <span class="mi">100</span><span class="p">,</span> <span class="nb">p3</span><span class="p">,</span> <span class="mi">1000</span> a<span class="n">sw</span> <span class="nb">vco2</span> <span class="nb">k</span><span class="p">(</span>a<span class="n">1</span><span class="p">),</span> k<span class="n">s</span> <span class="cm">/* every hopsize samples */</span> <span class="k">if</span> k<span class="n">cnt</span> <span class="o">==</span> i<span class="n">hopsize</span> <span class="k">then</span> <span class="cm">/* window and take FFT */</span> k<span class="n">Win</span><span class="p">[]</span> <span class="nb">window</span> k<span class="n">In</span><span class="p">,</span>k<span class="n">row</span><span class="o">*</span>i<span class="n">hopsize</span> k<span class="n">Spec</span><span class="p">[]</span> <span class="nb">rfft</span> k<span class="n">Win</span> k<span class="n">Win</span> <span class="nb">window</span> k<span class="n">Sw</span><span class="p">,</span>k<span class="n">row</span><span class="o">*</span>i<span class="n">hopsize</span> k<span class="n">Spec2</span><span class="p">[]</span> <span class="nb">rfft</span> k<span class="n">Win</span> k<span class="n">Prod</span><span class="p">[]</span> <span class="nb">cmplxprod</span> k<span class="n">Spec</span><span class="p">,</span> k<span class="n">Spec2</span> <span class="cm">/* IFFT + window */</span> k<span class="n">Row</span><span class="p">[]</span> <span class="nb">rifft</span> k<span class="n">Prod</span> k<span class="n">Win</span> <span class="nb">window</span> k<span class="n">Row</span><span class="p">,</span> k<span class="n">row</span><span class="o">*</span>i<span class="n">hopsize</span> <span class="cm">/* place it on out buffer */</span> k<span class="n">Out</span> <span class="nb">setrow</span> k<span class="n">Win</span><span class="p">,</span> k<span class="n">row</span> <span class="cm">/* zero the ola buffer */</span> k<span class="n">Ola</span> <span class="o">=</span> <span class="mi">0</span> <span class="cm">/* overlap-add */</span> k<span class="n">i</span> <span class="o">=</span> <span class="mi">0</span> <span class="k">until</span> k<span class="n">i</span> <span class="o">==</span> i<span class="n">olaps</span> <span class="k">do</span> k<span class="n">Row</span> <span class="nb">getrow</span> k<span class="n">Out</span><span class="p">,</span> k<span class="n">i</span> k<span class="n">Ola</span> <span class="o">=</span> k<span class="n">Ola</span> <span class="o">+</span> k<span class="n">Row</span> k<span class="n">i</span> <span class="o">+=</span> <span class="mi">1</span> <span class="k">od</span> <span class="cm">/* update counters */</span> k<span class="n">row</span> <span class="o">=</span> <span class="p">(</span>k<span class="n">row</span><span class="o">+</span><span class="mi">1</span><span class="p">)</span><span class="o">%</span>i<span class="n">olaps</span> k<span class="n">cnt</span> <span class="o">=</span> <span class="mi">0</span> <span class="k">endif</span> <span class="cm">/* shift audio in/out of buffers */</span> k<span class="n">In</span> <span class="nb">shiftin</span> a<span class="n">1</span> k<span class="n">Sw</span> <span class="nb">shiftin</span> a<span class="n">sw</span> a<span class="n">2</span> <span class="nb">shiftout</span> k<span class="n">Ola</span> <span class="nb">out</span> a<span class="n">2</span><span class="o">/</span>i<span class="n">olaps</span> <span class="cm">/* increment counter */</span> k<span class="n">cnt</span> <span class="o">+=</span> <span class="vg">ksmps</span> <span class="kd">endin</span> <span class="nt"></CsInstruments></span> <span class="nt"><CsScore></span> <span class="nb">i</span><span class="mi">1</span> <span class="mi">0</span> <span class="mi">10</span> <span class="nt"></CsScore></span> <span class="nt"></CsoundSynthesizer></span> </pre> </div> </div> </div> <br class="example-break" /> </div> <div class="refsect1"> <a id="idm281472894570920"></a> <h2>See Also</h2> <p> <a class="link" href="vectorial.html" title="Vectorial Opcodes"><em class="citetitle"></em>Vectorial opcodes</a>, <a class="link" href="arrayOpcodes.html" title="Array Opcodes"><em class="citetitle"></em>array opcodes</a> </p> </div> <div class="refsect1"> <a id="idm281472894567912"></a> <h2>Credits</h2> <p> </p> <table border="0" summary="Simple list" class="simplelist"> <tr> <td>Author: Victor Lazzarini</td> </tr> <tr> <td>NUI Maynooth</td> </tr> <tr> <td>2014</td> </tr> </table> <p> </p> <p>New in version 6.04</p> </div> </div> <div class="navfooter"> <hr /> <table width="100%" summary="Navigation footer"> <tr> <td width="40%" align="left"><a accesskey="p" href="rezzy.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="rifft.html">Next</a></td> </tr> <tr> <td width="40%" align="left" valign="top">rezzy </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> <td width="40%" align="right" valign="top"> rifft</td> </tr> </table> </div> </body> </html>