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<a href="#id2585410" class="shortcut">Description</a></nobr></td></tr>
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<div class="refentry" lang="en">
<a name="gst-plugins-base-libs-gstffts16"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2>
<a name="id2584324"></a><span class="refentrytitle">gstffts16</span>
</h2>
<p>gstffts16 — FFT functions for signed 16 bit integer samples</p>
</td>
<td valign="top" align="right"></td>
</tr></table></div>
<div class="refsynopsisdiv">
<h2>Synopsis</h2>
<pre class="synopsis">
#include <gst/fft/gstffts16.h>
<a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16">GstFFTS16</a>;
<a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16Complex">GstFFTS16Complex</a>;
<a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16">GstFFTS16</a>* <a href="gst-plugins-base-libs-gstffts16.html#gst-fft-s16-new">gst_fft_s16_new</a> (gint len,
gboolean inverse);
void <a href="gst-plugins-base-libs-gstffts16.html#gst-fft-s16-fft">gst_fft_s16_fft</a> (<a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16">GstFFTS16</a> *self,
const gint16 *timedata,
<a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16Complex">GstFFTS16Complex</a> *freqdata);
void <a href="gst-plugins-base-libs-gstffts16.html#gst-fft-s16-inverse-fft">gst_fft_s16_inverse_fft</a> (<a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16">GstFFTS16</a> *self,
const <a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16Complex">GstFFTS16Complex</a> *freqdata,
gint16 *timedata);
void <a href="gst-plugins-base-libs-gstffts16.html#gst-fft-s16-window">gst_fft_s16_window</a> (<a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16">GstFFTS16</a> *self,
gint16 *timedata,
<a href="gst-plugins-base-libs-gstfft.html#GstFFTWindow">GstFFTWindow</a> window);
void <a href="gst-plugins-base-libs-gstffts16.html#gst-fft-s16-free">gst_fft_s16_free</a> (<a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16">GstFFTS16</a> *self);
</pre>
</div>
<div class="refsect1" lang="en">
<a name="id2585410"></a><h2>Description</h2>
<p>
<a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16"><span class="type">GstFFTS16</span></a> provides a FFT implementation and related functions for
signed 16 bit integer samples. To use this call <a href="gst-plugins-base-libs-gstffts16.html#gst-fft-s16-new"><code class="function">gst_fft_s16_new()</code></a> for
allocating a <a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16"><span class="type">GstFFTS16</span></a> instance with the appropiate parameters and
then call <a href="gst-plugins-base-libs-gstffts16.html#gst-fft-s16-fft"><code class="function">gst_fft_s16_fft()</code></a> or <a href="gst-plugins-base-libs-gstffts16.html#gst-fft-s16-inverse-fft"><code class="function">gst_fft_s16_inverse_fft()</code></a> to perform the
FFT or inverse FFT on a buffer of samples.
</p>
<p>
After use free the <a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16"><span class="type">GstFFTS16</span></a> instance with <a href="gst-plugins-base-libs-gstffts16.html#gst-fft-s16-free"><code class="function">gst_fft_s16_free()</code></a>.
</p>
<p>
For the best performance use <a href="gst-plugins-base-libs-gstfft.html#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 href="gst-plugins-base-libs-gstffts16.html#gst-fft-s16-new"><code class="function">gst_fft_s16_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 href="gst-plugins-base-libs-gstffts16.html#gst-fft-s16-window"><code class="function">gst_fft_s16_window()</code></a> can comfortably
be used.
</p>
<p>
Be aware, that you can't simply run <a href="gst-plugins-base-libs-gstffts16.html#gst-fft-s16-inverse-fft"><code class="function">gst_fft_s16_inverse_fft()</code></a> on the
resulting frequency data of <a href="gst-plugins-base-libs-gstffts16.html#gst-fft-s16-fft"><code class="function">gst_fft_s16_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>
<p>
</p>
</div>
<div class="refsect1" lang="en">
<a name="id2585604"></a><h2>Details</h2>
<div class="refsect2" lang="en">
<a name="id2585614"></a><h3>
<a name="GstFFTS16"></a>GstFFTS16</h3>
<a class="indexterm" name="id2585626"></a><pre class="programlisting">typedef struct {
} GstFFTS16;
</pre>
<p>
Instance structure for <a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16"><span class="type">GstFFTS16</span></a>.</p>
<p>
</p>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2585653"></a><h3>
<a name="GstFFTS16Complex"></a>GstFFTS16Complex</h3>
<a class="indexterm" name="id2585666"></a><pre class="programlisting">typedef struct {
gint16 r;
gint16 i;
} GstFFTS16Complex;
</pre>
<p>
Data type for complex numbers composed of
signed 16 bit integers.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><span class="term">gint16 <em class="structfield"><code>r</code></em>;</span></td>
<td> Real part
</td>
</tr>
<tr>
<td><span class="term">gint16 <em class="structfield"><code>i</code></em>;</span></td>
<td> Imaginary part
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2585731"></a><h3>
<a name="gst-fft-s16-new"></a>gst_fft_s16_new ()</h3>
<a class="indexterm" name="id2585744"></a><pre class="programlisting"><a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16">GstFFTS16</a>* gst_fft_s16_new (gint len,
gboolean inverse);</pre>
<p>
This returns a new <a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16"><span class="type">GstFFTS16</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 href="gst-plugins-base-libs-gstfft.html#gst-fft-next-fast-length"><code class="function">gst_fft_next_fast_length()</code></a>.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><span class="term"><em class="parameter"><code>len</code></em> :</span></td>
<td> Length of the FFT in the time domain
</td>
</tr>
<tr>
<td><span class="term"><em class="parameter"><code>inverse</code></em> :</span></td>
<td> <code class="literal">TRUE</code> if the <a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16"><span class="type">GstFFTS16</span></a> instance should be used for the inverse FFT
</td>
</tr>
<tr>
<td><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td>
<td> a new <a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16"><span class="type">GstFFTS16</span></a> instance.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2585884"></a><h3>
<a name="gst-fft-s16-fft"></a>gst_fft_s16_fft ()</h3>
<a class="indexterm" name="id2585897"></a><pre class="programlisting">void gst_fft_s16_fft (<a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16">GstFFTS16</a> *self,
const gint16 *timedata,
<a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16Complex">GstFFTS16Complex</a> *freqdata);</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 href="gst-plugins-base-libs-gstffts16.html#GstFFTS16"><span class="type">GstFFTS16</span></a> instance with <a href="gst-plugins-base-libs-gstffts16.html#gst-fft-s16-new"><code class="function">gst_fft_s16_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 href="gst-plugins-base-libs-gstffts16.html#GstFFTS16Complex"><span class="type">GstFFTS16Complex</span></a> frequency
domain samples.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><span class="term"><em class="parameter"><code>self</code></em> :</span></td>
<td> <a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16"><span class="type">GstFFTS16</span></a> instance for this call
</td>
</tr>
<tr>
<td><span class="term"><em class="parameter"><code>timedata</code></em> :</span></td>
<td> Buffer of the samples in the time domain
</td>
</tr>
<tr>
<td><span class="term"><em class="parameter"><code>freqdata</code></em> :</span></td>
<td> Target buffer for the samples in the frequency domain
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2586071"></a><h3>
<a name="gst-fft-s16-inverse-fft"></a>gst_fft_s16_inverse_fft ()</h3>
<a class="indexterm" name="id2586084"></a><pre class="programlisting">void gst_fft_s16_inverse_fft (<a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16">GstFFTS16</a> *self,
const <a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16Complex">GstFFTS16Complex</a> *freqdata,
gint16 *timedata);</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 href="gst-plugins-base-libs-gstffts16.html#GstFFTS16"><span class="type">GstFFTS16</span></a> instance with <a href="gst-plugins-base-libs-gstffts16.html#gst-fft-s16-new"><code class="function">gst_fft_s16_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>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><span class="term"><em class="parameter"><code>self</code></em> :</span></td>
<td> <a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16"><span class="type">GstFFTS16</span></a> instance for this call
</td>
</tr>
<tr>
<td><span class="term"><em class="parameter"><code>freqdata</code></em> :</span></td>
<td> Buffer of the samples in the frequency domain
</td>
</tr>
<tr>
<td><span class="term"><em class="parameter"><code>timedata</code></em> :</span></td>
<td> Target buffer for the samples in the time domain
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2586255"></a><h3>
<a name="gst-fft-s16-window"></a>gst_fft_s16_window ()</h3>
<a class="indexterm" name="id2586268"></a><pre class="programlisting">void gst_fft_s16_window (<a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16">GstFFTS16</a> *self,
gint16 *timedata,
<a href="gst-plugins-base-libs-gstfft.html#GstFFTWindow">GstFFTWindow</a> window);</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>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><span class="term"><em class="parameter"><code>self</code></em> :</span></td>
<td> <a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16"><span class="type">GstFFTS16</span></a> instance for this call
</td>
</tr>
<tr>
<td><span class="term"><em class="parameter"><code>timedata</code></em> :</span></td>
<td> Time domain samples
</td>
</tr>
<tr>
<td><span class="term"><em class="parameter"><code>window</code></em> :</span></td>
<td> Window function to apply
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2586382"></a><h3>
<a name="gst-fft-s16-free"></a>gst_fft_s16_free ()</h3>
<a class="indexterm" name="id2586395"></a><pre class="programlisting">void gst_fft_s16_free (<a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16">GstFFTS16</a> *self);</pre>
<p>
This frees the memory allocated for <em class="parameter"><code>self</code></em>.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody><tr>
<td><span class="term"><em class="parameter"><code>self</code></em> :</span></td>
<td> <a href="gst-plugins-base-libs-gstffts16.html#GstFFTS16"><span class="type">GstFFTS16</span></a> instance for this call
</td>
</tr></tbody>
</table></div>
</div>
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