<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>gstfftf32</title> <meta name="generator" content="DocBook XSL Stylesheets V1.76.1"> <link rel="home" href="index.html" title="GStreamer Base Plugins 0.10 Library Reference Manual"> <link rel="up" href="gstreamer-ffft.html" title="FFT Library"> <link rel="prev" href="gst-plugins-base-libs-gstffts32.html" title="gstffts32"> <link rel="next" href="gst-plugins-base-libs-gstfftf64.html" title="gstfftf64"> <meta name="generator" content="GTK-Doc V1.18 (XML mode)"> <link rel="stylesheet" href="style.css" type="text/css"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <table class="navigation" id="top" width="100%" summary="Navigation header" cellpadding="2" cellspacing="2"> <tr valign="middle"> <td><a accesskey="p" href="gst-plugins-base-libs-gstffts32.html"><img src="left.png" width="24" height="24" border="0" alt="Prev"></a></td> <td><a accesskey="u" href="gstreamer-ffft.html"><img src="up.png" width="24" height="24" border="0" alt="Up"></a></td> <td><a accesskey="h" href="index.html"><img src="home.png" width="24" height="24" border="0" alt="Home"></a></td> <th width="100%" align="center">GStreamer Base Plugins 0.10 Library Reference Manual</th> <td><a accesskey="n" href="gst-plugins-base-libs-gstfftf64.html"><img src="right.png" width="24" height="24" border="0" alt="Next"></a></td> </tr> <tr><td colspan="5" class="shortcuts"> <a href="#gst-plugins-base-libs-gstfftf32.synopsis" class="shortcut">Top</a> | <a href="#gst-plugins-base-libs-gstfftf32.description" class="shortcut">Description</a> </td></tr> </table> <div class="refentry"> <a name="gst-plugins-base-libs-gstfftf32"></a><div class="titlepage"></div> <div class="refnamediv"><table width="100%"><tr> <td valign="top"> <h2><span class="refentrytitle"><a name="gst-plugins-base-libs-gstfftf32.top_of_page"></a>gstfftf32</span></h2> <p>gstfftf32 — FFT functions for 32 bit float samples</p> </td> <td valign="top" align="right"></td> </tr></table></div> <div class="refsynopsisdiv"> <a name="gst-plugins-base-libs-gstfftf32.synopsis"></a><h2>Synopsis</h2> <pre class="synopsis"> #include <gst/fft/gstfftf32.h> struct <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32">GstFFTF32</a>; struct <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32Complex" title="struct GstFFTF32Complex">GstFFTF32Complex</a>; <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="returnvalue">GstFFTF32</span></a> * <a class="link" href="gst-plugins-base-libs-gstfftf32.html#gst-fft-f32-new" title="gst_fft_f32_new ()">gst_fft_f32_new</a> (<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gint"><span class="type">gint</span></a> len</code></em>, <em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="type">gboolean</span></a> inverse</code></em>); <span class="returnvalue">void</span> <a class="link" href="gst-plugins-base-libs-gstfftf32.html#gst-fft-f32-fft" title="gst_fft_f32_fft ()">gst_fft_f32_fft</a> (<em class="parameter"><code><a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a> *self</code></em>, <em class="parameter"><code>const <a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gfloat"><span class="type">gfloat</span></a> *timedata</code></em>, <em class="parameter"><code><a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32Complex" title="struct GstFFTF32Complex"><span class="type">GstFFTF32Complex</span></a> *freqdata</code></em>); <span class="returnvalue">void</span> <a class="link" href="gst-plugins-base-libs-gstfftf32.html#gst-fft-f32-inverse-fft" title="gst_fft_f32_inverse_fft ()">gst_fft_f32_inverse_fft</a> (<em class="parameter"><code><a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a> *self</code></em>, <em class="parameter"><code>const <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32Complex" title="struct GstFFTF32Complex"><span class="type">GstFFTF32Complex</span></a> *freqdata</code></em>, <em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gfloat"><span class="type">gfloat</span></a> *timedata</code></em>); <span class="returnvalue">void</span> <a class="link" href="gst-plugins-base-libs-gstfftf32.html#gst-fft-f32-window" title="gst_fft_f32_window ()">gst_fft_f32_window</a> (<em class="parameter"><code><a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a> *self</code></em>, <em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gfloat"><span class="type">gfloat</span></a> *timedata</code></em>, <em class="parameter"><code><a class="link" href="gst-plugins-base-libs-gstfft.html#GstFFTWindow" title="enum GstFFTWindow"><span class="type">GstFFTWindow</span></a> window</code></em>); <span class="returnvalue">void</span> <a class="link" href="gst-plugins-base-libs-gstfftf32.html#gst-fft-f32-free" title="gst_fft_f32_free ()">gst_fft_f32_free</a> (<em class="parameter"><code><a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a> *self</code></em>); </pre> </div> <div class="refsect1"> <a name="gst-plugins-base-libs-gstfftf32.description"></a><h2>Description</h2> <p> <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a> provides a FFT implementation and related functions for 32 bit float samples. To use this call <a class="link" href="gst-plugins-base-libs-gstfftf32.html#gst-fft-f32-new" title="gst_fft_f32_new ()"><code class="function">gst_fft_f32_new()</code></a> for allocating a <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a> instance with the appropriate parameters and then call <a class="link" href="gst-plugins-base-libs-gstfftf32.html#gst-fft-f32-fft" title="gst_fft_f32_fft ()"><code class="function">gst_fft_f32_fft()</code></a> or <a class="link" href="gst-plugins-base-libs-gstfftf32.html#gst-fft-f32-inverse-fft" title="gst_fft_f32_inverse_fft ()"><code class="function">gst_fft_f32_inverse_fft()</code></a> to perform the FFT or inverse FFT on a buffer of samples. </p> <p> After use free the <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a> instance with <a class="link" href="gst-plugins-base-libs-gstfftf32.html#gst-fft-f32-free" title="gst_fft_f32_free ()"><code class="function">gst_fft_f32_free()</code></a>. </p> <p> For the best performance use <a class="link" href="gst-plugins-base-libs-gstfft.html#gst-fft-next-fast-length" title="gst_fft_next_fast_length ()"><code class="function">gst_fft_next_fast_length()</code></a> to get a number that is entirely a product of 2, 3 and 5 and use this as the <em class="parameter"><code>len</code></em> parameter for <a class="link" href="gst-plugins-base-libs-gstfftf32.html#gst-fft-f32-new" title="gst_fft_f32_new ()"><code class="function">gst_fft_f32_new()</code></a>. </p> <p> The <em class="parameter"><code>len</code></em> parameter specifies the number of samples in the time domain that will be processed or generated. The number of samples in the frequency domain is <em class="parameter"><code>len</code></em>/2 + 1. To get n samples in the frequency domain use 2*n - 2 as <em class="parameter"><code>len</code></em>. </p> <p> Before performing the FFT on time domain data it usually makes sense to apply a window function to it. For this <a class="link" href="gst-plugins-base-libs-gstfftf32.html#gst-fft-f32-window" title="gst_fft_f32_window ()"><code class="function">gst_fft_f32_window()</code></a> can comfortably be used. </p> <p> Be aware, that you can't simply run <a class="link" href="gst-plugins-base-libs-gstfftf32.html#gst-fft-f32-inverse-fft" title="gst_fft_f32_inverse_fft ()"><code class="function">gst_fft_f32_inverse_fft()</code></a> on the resulting frequency data of <a class="link" href="gst-plugins-base-libs-gstfftf32.html#gst-fft-f32-fft" title="gst_fft_f32_fft ()"><code class="function">gst_fft_f32_fft()</code></a> to get the original data back. The relation between them is iFFT (FFT (x)) = x * nfft where nfft is the length of the FFT. This also has to be taken into account when calculation the magnitude of the frequency data. </p> </div> <div class="refsect1"> <a name="gst-plugins-base-libs-gstfftf32.details"></a><h2>Details</h2> <div class="refsect2"> <a name="GstFFTF32"></a><h3>struct GstFFTF32</h3> <pre class="programlisting">struct GstFFTF32 { }; </pre> <p> Instance structure for <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a>. </p> </div> <hr> <div class="refsect2"> <a name="GstFFTF32Complex"></a><h3>struct GstFFTF32Complex</h3> <pre class="programlisting">struct GstFFTF32Complex { gfloat r; gfloat i; }; </pre> <p> Data type for complex numbers composed of 32 bit float. </p> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody> <tr> <td><p><span class="term"><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gfloat"><span class="type">gfloat</span></a> <em class="structfield"><code><a name="GstFFTF32Complex.r"></a>r</code></em>;</span></p></td> <td>Real part</td> </tr> <tr> <td><p><span class="term"><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gfloat"><span class="type">gfloat</span></a> <em class="structfield"><code><a name="GstFFTF32Complex.i"></a>i</code></em>;</span></p></td> <td>Imaginary part</td> </tr> </tbody> </table></div> </div> <hr> <div class="refsect2"> <a name="gst-fft-f32-new"></a><h3>gst_fft_f32_new ()</h3> <pre class="programlisting"><a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="returnvalue">GstFFTF32</span></a> * gst_fft_f32_new (<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gint"><span class="type">gint</span></a> len</code></em>, <em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="type">gboolean</span></a> inverse</code></em>);</pre> <p> This returns a new <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a> instance with the given parameters. It makes sense to keep one instance for several calls for speed reasons. </p> <p> <em class="parameter"><code>len</code></em> must be even and to get the best performance a product of 2, 3 and 5. To get the next number with this characteristics use <a class="link" href="gst-plugins-base-libs-gstfft.html#gst-fft-next-fast-length" title="gst_fft_next_fast_length ()"><code class="function">gst_fft_next_fast_length()</code></a>. </p> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody> <tr> <td><p><span class="term"><em class="parameter"><code>len</code></em> :</span></p></td> <td>Length of the FFT in the time domain</td> </tr> <tr> <td><p><span class="term"><em class="parameter"><code>inverse</code></em> :</span></p></td> <td> <a href="http://library.gnome.org/devel/glib/unstable/glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> if the <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a> instance should be used for the inverse FFT</td> </tr> <tr> <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> <td>a new <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a> instance.</td> </tr> </tbody> </table></div> </div> <hr> <div class="refsect2"> <a name="gst-fft-f32-fft"></a><h3>gst_fft_f32_fft ()</h3> <pre class="programlisting"><span class="returnvalue">void</span> gst_fft_f32_fft (<em class="parameter"><code><a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a> *self</code></em>, <em class="parameter"><code>const <a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gfloat"><span class="type">gfloat</span></a> *timedata</code></em>, <em class="parameter"><code><a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32Complex" title="struct GstFFTF32Complex"><span class="type">GstFFTF32Complex</span></a> *freqdata</code></em>);</pre> <p> This performs the FFT on <em class="parameter"><code>timedata</code></em> and puts the result in <em class="parameter"><code>freqdata</code></em>. </p> <p> <em class="parameter"><code>timedata</code></em> must have as many samples as specified with the <em class="parameter"><code>len</code></em> parameter while allocating the <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a> instance with <a class="link" href="gst-plugins-base-libs-gstfftf32.html#gst-fft-f32-new" title="gst_fft_f32_new ()"><code class="function">gst_fft_f32_new()</code></a>. </p> <p> <em class="parameter"><code>freqdata</code></em> must be large enough to hold <em class="parameter"><code>len</code></em>/2 + 1 <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32Complex" title="struct GstFFTF32Complex"><span class="type">GstFFTF32Complex</span></a> frequency domain samples. </p> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody> <tr> <td><p><span class="term"><em class="parameter"><code>self</code></em> :</span></p></td> <td> <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a> instance for this call</td> </tr> <tr> <td><p><span class="term"><em class="parameter"><code>timedata</code></em> :</span></p></td> <td>Buffer of the samples in the time domain</td> </tr> <tr> <td><p><span class="term"><em class="parameter"><code>freqdata</code></em> :</span></p></td> <td>Target buffer for the samples in the frequency domain</td> </tr> </tbody> </table></div> </div> <hr> <div class="refsect2"> <a name="gst-fft-f32-inverse-fft"></a><h3>gst_fft_f32_inverse_fft ()</h3> <pre class="programlisting"><span class="returnvalue">void</span> gst_fft_f32_inverse_fft (<em class="parameter"><code><a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a> *self</code></em>, <em class="parameter"><code>const <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32Complex" title="struct GstFFTF32Complex"><span class="type">GstFFTF32Complex</span></a> *freqdata</code></em>, <em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gfloat"><span class="type">gfloat</span></a> *timedata</code></em>);</pre> <p> This performs the inverse FFT on <em class="parameter"><code>freqdata</code></em> and puts the result in <em class="parameter"><code>timedata</code></em>. </p> <p> <em class="parameter"><code>freqdata</code></em> must have <em class="parameter"><code>len</code></em>/2 + 1 samples, where <em class="parameter"><code>len</code></em> is the parameter specified while allocating the <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a> instance with <a class="link" href="gst-plugins-base-libs-gstfftf32.html#gst-fft-f32-new" title="gst_fft_f32_new ()"><code class="function">gst_fft_f32_new()</code></a>. </p> <p> <em class="parameter"><code>timedata</code></em> must be large enough to hold <em class="parameter"><code>len</code></em> time domain samples. </p> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody> <tr> <td><p><span class="term"><em class="parameter"><code>self</code></em> :</span></p></td> <td> <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a> instance for this call</td> </tr> <tr> <td><p><span class="term"><em class="parameter"><code>freqdata</code></em> :</span></p></td> <td>Buffer of the samples in the frequency domain</td> </tr> <tr> <td><p><span class="term"><em class="parameter"><code>timedata</code></em> :</span></p></td> <td>Target buffer for the samples in the time domain</td> </tr> </tbody> </table></div> </div> <hr> <div class="refsect2"> <a name="gst-fft-f32-window"></a><h3>gst_fft_f32_window ()</h3> <pre class="programlisting"><span class="returnvalue">void</span> gst_fft_f32_window (<em class="parameter"><code><a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a> *self</code></em>, <em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gfloat"><span class="type">gfloat</span></a> *timedata</code></em>, <em class="parameter"><code><a class="link" href="gst-plugins-base-libs-gstfft.html#GstFFTWindow" title="enum GstFFTWindow"><span class="type">GstFFTWindow</span></a> window</code></em>);</pre> <p> This calls the window function <em class="parameter"><code>window</code></em> on the <em class="parameter"><code>timedata</code></em> sample buffer. </p> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody> <tr> <td><p><span class="term"><em class="parameter"><code>self</code></em> :</span></p></td> <td> <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a> instance for this call</td> </tr> <tr> <td><p><span class="term"><em class="parameter"><code>timedata</code></em> :</span></p></td> <td>Time domain samples</td> </tr> <tr> <td><p><span class="term"><em class="parameter"><code>window</code></em> :</span></p></td> <td>Window function to apply</td> </tr> </tbody> </table></div> </div> <hr> <div class="refsect2"> <a name="gst-fft-f32-free"></a><h3>gst_fft_f32_free ()</h3> <pre class="programlisting"><span class="returnvalue">void</span> gst_fft_f32_free (<em class="parameter"><code><a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a> *self</code></em>);</pre> <p> This frees the memory allocated for <em class="parameter"><code>self</code></em>. </p> <div class="variablelist"><table border="0"> <col align="left" valign="top"> <tbody><tr> <td><p><span class="term"><em class="parameter"><code>self</code></em> :</span></p></td> <td> <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a> instance for this call</td> </tr></tbody> </table></div> </div> </div> </div> <div class="footer"> <hr> Generated by GTK-Doc V1.18</div> </body> </html>