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<h1>libfft.h</h1> </div>
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<a href="libfft_8h.html">Go to the documentation of this file.</a><div class="fragment"><pre class="fragment"><a name="l00001"></a>00001 <span class="comment">/* -------------------------------------------------------------- */</span>
<a name="l00002"></a>00002 <span class="comment">/* (C)Copyright 2008 Free Software Foundation, Inc. */</span>
<a name="l00003"></a>00003 <span class="comment">/* (C)Copyright 2001,2007, */</span>
<a name="l00004"></a>00004 <span class="comment">/* International Business Machines Corporation, */</span>
<a name="l00005"></a>00005 <span class="comment">/* Sony Computer Entertainment, Incorporated, */</span>
<a name="l00006"></a>00006 <span class="comment">/* Toshiba Corporation, */</span>
<a name="l00007"></a>00007 <span class="comment">/* */</span>
<a name="l00008"></a>00008 <span class="comment">/* All Rights Reserved. */</span>
<a name="l00009"></a>00009 <span class="comment">/* */</span>
<a name="l00010"></a>00010 <span class="comment">/* Redistribution and use in source and binary forms, with or */</span>
<a name="l00011"></a>00011 <span class="comment">/* without modification, are permitted provided that the */</span>
<a name="l00012"></a>00012 <span class="comment">/* following conditions are met: */</span>
<a name="l00013"></a>00013 <span class="comment">/* */</span>
<a name="l00014"></a>00014 <span class="comment">/* - Redistributions of source code must retain the above copyright*/</span>
<a name="l00015"></a>00015 <span class="comment">/* notice, this list of conditions and the following disclaimer. */</span>
<a name="l00016"></a>00016 <span class="comment">/* */</span>
<a name="l00017"></a>00017 <span class="comment">/* - Redistributions in binary form must reproduce the above */</span>
<a name="l00018"></a>00018 <span class="comment">/* copyright notice, this list of conditions and the following */</span>
<a name="l00019"></a>00019 <span class="comment">/* disclaimer in the documentation and/or other materials */</span>
<a name="l00020"></a>00020 <span class="comment">/* provided with the distribution. */</span>
<a name="l00021"></a>00021 <span class="comment">/* */</span>
<a name="l00022"></a>00022 <span class="comment">/* - Neither the name of IBM Corporation nor the names of its */</span>
<a name="l00023"></a>00023 <span class="comment">/* contributors may be used to endorse or promote products */</span>
<a name="l00024"></a>00024 <span class="comment">/* derived from this software without specific prior written */</span>
<a name="l00025"></a>00025 <span class="comment">/* permission. */</span>
<a name="l00026"></a>00026 <span class="comment">/* */</span>
<a name="l00027"></a>00027 <span class="comment">/* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND */</span>
<a name="l00028"></a>00028 <span class="comment">/* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, */</span>
<a name="l00029"></a>00029 <span class="comment">/* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF */</span>
<a name="l00030"></a>00030 <span class="comment">/* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE */</span>
<a name="l00031"></a>00031 <span class="comment">/* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR */</span>
<a name="l00032"></a>00032 <span class="comment">/* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, */</span>
<a name="l00033"></a>00033 <span class="comment">/* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT */</span>
<a name="l00034"></a>00034 <span class="comment">/* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; */</span>
<a name="l00035"></a>00035 <span class="comment">/* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) */</span>
<a name="l00036"></a>00036 <span class="comment">/* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN */</span>
<a name="l00037"></a>00037 <span class="comment">/* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR */</span>
<a name="l00038"></a>00038 <span class="comment">/* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, */</span>
<a name="l00039"></a>00039 <span class="comment">/* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */</span>
<a name="l00040"></a>00040 <span class="comment">/* -------------------------------------------------------------- */</span>
<a name="l00041"></a>00041 <span class="comment">/* PROLOG END TAG zYx */</span>
<a name="l00042"></a>00042
<a name="l00043"></a>00043 <span class="preprocessor">#ifndef INCLUDED_LIBFFT_H</span>
<a name="l00044"></a>00044 <span class="preprocessor"></span><span class="preprocessor">#define INCLUDED_LIBFFT_H</span>
<a name="l00045"></a>00045 <span class="preprocessor"></span>
<a name="l00046"></a>00046 <span class="comment">// must be defined before inclusion of fft_1d_r2.h</span>
<a name="l00047"></a><a class="code" href="libfft_8h.html#a7e49143d089320690fd74371ce28048b">00047</a> <span class="preprocessor">#define MAX_FFT_1D_SIZE 4096</span>
<a name="l00048"></a>00048 <span class="preprocessor"></span>
<a name="l00049"></a>00049 <span class="comment">/* fft_1d_r2</span>
<a name="l00050"></a>00050 <span class="comment"> * ---------</span>
<a name="l00051"></a>00051 <span class="comment"> * Performs a single precision, complex Fast Fourier Transform using </span>
<a name="l00052"></a>00052 <span class="comment"> * the DFT (Discrete Fourier Transform) with radix-2 decimation in time. </span>
<a name="l00053"></a>00053 <span class="comment"> * The input <in> is an array of complex numbers of length (1<<log2_size)</span>
<a name="l00054"></a>00054 <span class="comment"> * entries. The result is returned in the array of complex numbers specified</span>
<a name="l00055"></a>00055 <span class="comment"> * by <out>. Note: This routine can support an in-place transformation</span>
<a name="l00056"></a>00056 <span class="comment"> * by specifying <in> and <out> to be the same array.</span>
<a name="l00057"></a>00057 <span class="comment"> *</span>
<a name="l00058"></a>00058 <span class="comment"> * This implementation utilizes the Cooley-Tukey algorithm consisting </span>
<a name="l00059"></a>00059 <span class="comment"> * of <log2_size> stages. The basic operation is the butterfly.</span>
<a name="l00060"></a>00060 <span class="comment"> *</span>
<a name="l00061"></a>00061 <span class="comment"> * p --------------------------> P = p + q*Wi</span>
<a name="l00062"></a>00062 <span class="comment"> * \ /</span>
<a name="l00063"></a>00063 <span class="comment"> * \ /</span>
<a name="l00064"></a>00064 <span class="comment"> * \ /</span>
<a name="l00065"></a>00065 <span class="comment"> * \/</span>
<a name="l00066"></a>00066 <span class="comment"> * /\</span>
<a name="l00067"></a>00067 <span class="comment"> * / \</span>
<a name="l00068"></a>00068 <span class="comment"> * / \</span>
<a name="l00069"></a>00069 <span class="comment"> * ____ / \</span>
<a name="l00070"></a>00070 <span class="comment"> * q --| Wi |-----------------> Q = p - q*Wi</span>
<a name="l00071"></a>00071 <span class="comment"> * ----</span>
<a name="l00072"></a>00072 <span class="comment"> *</span>
<a name="l00073"></a>00073 <span class="comment"> * This routine also requires pre-computed twiddle values, W. W is an</span>
<a name="l00074"></a>00074 <span class="comment"> * array of single precision complex numbers of length 1<<(log2_size-2) </span>
<a name="l00075"></a>00075 <span class="comment"> * and is computed as follows:</span>
<a name="l00076"></a>00076 <span class="comment"> *</span>
<a name="l00077"></a>00077 <span class="comment"> * for (i=0; i<n/4; i++)</span>
<a name="l00078"></a>00078 <span class="comment"> * W[i].real = cos(i * 2*PI/n);</span>
<a name="l00079"></a>00079 <span class="comment"> * W[i].imag = -sin(i * 2*PI/n);</span>
<a name="l00080"></a>00080 <span class="comment"> * }</span>
<a name="l00081"></a>00081 <span class="comment"> *</span>
<a name="l00082"></a>00082 <span class="comment"> * This array actually only contains the first half of the twiddle</span>
<a name="l00083"></a>00083 <span class="comment"> * factors. Due for symmetry, the second half of the twiddle factors</span>
<a name="l00084"></a>00084 <span class="comment"> * are implied and equal:</span>
<a name="l00085"></a>00085 <span class="comment"> *</span>
<a name="l00086"></a>00086 <span class="comment"> * for (i=0; i<n/4; i++)</span>
<a name="l00087"></a>00087 <span class="comment"> * W[i+n/4].real = W[i].imag = sin(i * 2*PI/n);</span>
<a name="l00088"></a>00088 <span class="comment"> * W[i+n/4].imag = -W[i].real = -cos(i * 2*PI/n);</span>
<a name="l00089"></a>00089 <span class="comment"> * }</span>
<a name="l00090"></a>00090 <span class="comment"> *</span>
<a name="l00091"></a>00091 <span class="comment"> * Further symmetry allows one to generate the twiddle factor table </span>
<a name="l00092"></a>00092 <span class="comment"> * using half the number of trig computations as follows:</span>
<a name="l00093"></a>00093 <span class="comment"> *</span>
<a name="l00094"></a>00094 <span class="comment"> * W[0].real = 1.0;</span>
<a name="l00095"></a>00095 <span class="comment"> * W[0].imag = 0.0;</span>
<a name="l00096"></a>00096 <span class="comment"> * for (i=1; i<n/4; i++)</span>
<a name="l00097"></a>00097 <span class="comment"> * W[i].real = cos(i * 2*PI/n);</span>
<a name="l00098"></a>00098 <span class="comment"> * W[n/4 - i].imag = -W[i].real;</span>
<a name="l00099"></a>00099 <span class="comment"> * }</span>
<a name="l00100"></a>00100 <span class="comment"> *</span>
<a name="l00101"></a>00101 <span class="comment"> * The complex numbers are packed into quadwords as follows:</span>
<a name="l00102"></a>00102 <span class="comment"> *</span>
<a name="l00103"></a>00103 <span class="comment"> * quadword complex</span>
<a name="l00104"></a>00104 <span class="comment"> * array element array elements</span>
<a name="l00105"></a>00105 <span class="comment"> * -----------------------------------------------------</span>
<a name="l00106"></a>00106 <span class="comment"> * i | real 2*i | imag 2*i | real 2*i+1 | imag 2*i+1 | </span>
<a name="l00107"></a>00107 <span class="comment"> * -----------------------------------------------------</span>
<a name="l00108"></a>00108 <span class="comment"> *</span>
<a name="l00109"></a>00109 <span class="comment"> */</span>
<a name="l00110"></a>00110
<a name="l00111"></a>00111 <span class="keywordtype">void</span> <a class="code" href="libfft_8h.html#aa99ff84bbd0423c9c90ab56ee0d9272f">fft_1d_r2</a>(vector <span class="keywordtype">float</span> *out, vector <span class="keywordtype">float</span> *in, vector <span class="keywordtype">float</span> *W, <span class="keywordtype">int</span> log2_size);
<a name="l00112"></a>00112
<a name="l00113"></a>00113 <span class="preprocessor">#endif </span><span class="comment">/* INCLUDED_LIBFFT_H */</span>
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