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  26                   <a href="#gst-plugins-base-libs-gstfftf32.description" class="shortcut">Description</a>
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  29 <div class="refentry">
  30 <a name="gst-plugins-base-libs-gstfftf32"></a><div class="titlepage"></div>
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  32 <td valign="top">
  33 <h2><span class="refentrytitle"><a name="gst-plugins-base-libs-gstfftf32.top_of_page"></a>gstfftf32</span></h2>
  34 <p>gstfftf32 — FFT functions for 32 bit float samples</p>
  35 </td>
  36 <td valign="top" align="right"></td>
  37 </tr></table></div>
  38 <div class="refsynopsisdiv">
  39 <a name="gst-plugins-base-libs-gstfftf32.synopsis"></a><h2>Synopsis</h2>
  40 <pre class="synopsis">
  41 #include &lt;gst/fft/gstfftf32.h&gt;
  42
  43 struct              <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32">GstFFTF32</a>;
  44 struct              <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32Complex" title="struct GstFFTF32Complex">GstFFTF32Complex</a>;
  45 <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>,
  46                                                          <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>);
  47 <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>,
  48                                                          <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>,
  49                                                          <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>);
  50 <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>,
  51                                                          <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>,
  52                                                          <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>);
  53 <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>,
  54                                                          <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>,
  55                                                          <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>);
  56 <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>);
  57 </pre>
  58 </div>
  59 <div class="refsect1">
  60 <a name="gst-plugins-base-libs-gstfftf32.description"></a><h2>Description</h2>
  61 <p>
  62 <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
  63 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
  64 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
  65 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
  66 FFT or inverse FFT on a buffer of samples.
  67 </p>
  68 <p>
  69 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>.
  70 </p>
  71 <p>
  72 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
  73 number that is entirely a product of 2, 3 and 5 and use this as the
  74 <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>.
  75 </p>
  76 <p>
  77 The <em class="parameter"><code>len</code></em> parameter specifies the number of samples in the time domain that
  78 will be processed or generated. The number of samples in the frequency domain
  79 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>.
  80 </p>
  81 <p>
  82 Before performing the FFT on time domain data it usually makes sense
  83 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
  84 be used.
  85 </p>
  86 <p>
  87 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
  88 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.
  89 The relation between them is iFFT (FFT (x)) = x * nfft where nfft is the
  90 length of the FFT. This also has to be taken into account when calculation
  91 the magnitude of the frequency data.
  92 </p>
  93 </div>
  94 <div class="refsect1">
  95 <a name="gst-plugins-base-libs-gstfftf32.details"></a><h2>Details</h2>
  96 <div class="refsect2">
  97 <a name="GstFFTF32"></a><h3>struct GstFFTF32</h3>
  98 <pre class="programlisting">struct GstFFTF32 {
  99 };
 100 </pre>
 101 <p>
 102 Instance structure for <a class="link" href="gst-plugins-base-libs-gstfftf32.html#GstFFTF32" title="struct GstFFTF32"><span class="type">GstFFTF32</span></a>.
 103 </p>
 104 </div>
 105 <hr>
 106 <div class="refsect2">
 107 <a name="GstFFTF32Complex"></a><h3>struct GstFFTF32Complex</h3>
 108 <pre class="programlisting">struct GstFFTF32Complex {
 109   gfloat r;
 110   gfloat i;
 111 };
 112 </pre>
 113 <p>
 114 Data type for complex numbers composed of
 115 32 bit float.
 116 </p>
 117 <div class="variablelist"><table border="0">
 118 <col align="left" valign="top">
 119 <tbody>
 120 <tr>
 121 <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>
 122 <td>Real part</td>
 123 </tr>
 124 <tr>
 125 <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>
 126 <td>Imaginary part</td>
 127 </tr>
 128 </tbody>
 129 </table></div>
 130 </div>
 131 <hr>
 132 <div class="refsect2">
 133 <a name="gst-fft-f32-new"></a><h3>gst_fft_f32_new ()</h3>
 134 <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>,
 135                                                          <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>
 136 <p>
 137 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
 138 sense to keep one instance for several calls for speed reasons.
 139 </p>
 140 <p>
 141 <em class="parameter"><code>len</code></em> must be even and to get the best performance a product of
 142 2, 3 and 5. To get the next number with this characteristics use
 143 <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>.
 144 </p>
 145 <div class="variablelist"><table border="0">
 146 <col align="left" valign="top">
 147 <tbody>
 148 <tr>
 149 <td><p><span class="term"><em class="parameter"><code>len</code></em> :</span></p></td>
 150 <td>Length of the FFT in the time domain</td>
 151 </tr>
 152 <tr>
 153 <td><p><span class="term"><em class="parameter"><code>inverse</code></em> :</span></p></td>
 154 <td>
 155 <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>
 156 </tr>
 157 <tr>
 158 <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
 159 <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>
 160 </tr>
 161 </tbody>
 162 </table></div>
 163 </div>
 164 <hr>
 165 <div class="refsect2">
 166 <a name="gst-fft-f32-fft"></a><h3>gst_fft_f32_fft ()</h3>
 167 <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>,
 168                                                          <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>,
 169                                                          <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>
 170 <p>
 171 This performs the FFT on <em class="parameter"><code>timedata</code></em> and puts the result in <em class="parameter"><code>freqdata</code></em>.
 172 </p>
 173 <p>
 174 <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
 175 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>.
 176 </p>
 177 <p>
 178 <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
 179 domain samples.
 180 </p>
 181 <div class="variablelist"><table border="0">
 182 <col align="left" valign="top">
 183 <tbody>
 184 <tr>
 185 <td><p><span class="term"><em class="parameter"><code>self</code></em> :</span></p></td>
 186 <td>
 187 <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>
 188 </tr>
 189 <tr>
 190 <td><p><span class="term"><em class="parameter"><code>timedata</code></em> :</span></p></td>
 191 <td>Buffer of the samples in the time domain</td>
 192 </tr>
 193 <tr>
 194 <td><p><span class="term"><em class="parameter"><code>freqdata</code></em> :</span></p></td>
 195 <td>Target buffer for the samples in the frequency domain</td>
 196 </tr>
 197 </tbody>
 198 </table></div>
 199 </div>
 200 <hr>
 201 <div class="refsect2">
 202 <a name="gst-fft-f32-inverse-fft"></a><h3>gst_fft_f32_inverse_fft ()</h3>
 203 <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>,
 204                                                          <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>,
 205                                                          <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>
 206 <p>
 207 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>.
 208 </p>
 209 <p>
 210 <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
 211 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>.
 212 </p>
 213 <p>
 214 <em class="parameter"><code>timedata</code></em> must be large enough to hold <em class="parameter"><code>len</code></em> time domain samples.
 215 </p>
 216 <div class="variablelist"><table border="0">
 217 <col align="left" valign="top">
 218 <tbody>
 219 <tr>
 220 <td><p><span class="term"><em class="parameter"><code>self</code></em> :</span></p></td>
 221 <td>
 222 <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>
 223 </tr>
 224 <tr>
 225 <td><p><span class="term"><em class="parameter"><code>freqdata</code></em> :</span></p></td>
 226 <td>Buffer of the samples in the frequency domain</td>
 227 </tr>
 228 <tr>
 229 <td><p><span class="term"><em class="parameter"><code>timedata</code></em> :</span></p></td>
 230 <td>Target buffer for the samples in the time domain</td>
 231 </tr>
 232 </tbody>
 233 </table></div>
 234 </div>
 235 <hr>
 236 <div class="refsect2">
 237 <a name="gst-fft-f32-window"></a><h3>gst_fft_f32_window ()</h3>
 238 <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>,
 239                                                          <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>,
 240                                                          <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>
 241 <p>
 242 This calls the window function <em class="parameter"><code>window</code></em> on the <em class="parameter"><code>timedata</code></em> sample buffer.
 243 </p>
 244 <div class="variablelist"><table border="0">
 245 <col align="left" valign="top">
 246 <tbody>
 247 <tr>
 248 <td><p><span class="term"><em class="parameter"><code>self</code></em> :</span></p></td>
 249 <td>
 250 <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>
 251 </tr>
 252 <tr>
 253 <td><p><span class="term"><em class="parameter"><code>timedata</code></em> :</span></p></td>
 254 <td>Time domain samples</td>
 255 </tr>
 256 <tr>
 257 <td><p><span class="term"><em class="parameter"><code>window</code></em> :</span></p></td>
 258 <td>Window function to apply</td>
 259 </tr>
 260 </tbody>
 261 </table></div>
 262 </div>
 263 <hr>
 264 <div class="refsect2">
 265 <a name="gst-fft-f32-free"></a><h3>gst_fft_f32_free ()</h3>
 266 <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>
 267 <p>
 268 This frees the memory allocated for <em class="parameter"><code>self</code></em>.
 269 </p>
 270 <div class="variablelist"><table border="0">
 271 <col align="left" valign="top">
 272 <tbody><tr>
 273 <td><p><span class="term"><em class="parameter"><code>self</code></em> :</span></p></td>
 274 <td>
 275 <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>
 276 </tr></tbody>
 277 </table></div>
 278 </div>
 279 </div>
 280 </div>
 281 <div class="footer">
 282 <hr>
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