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-rw-r--r--src/fft.c241
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diff --git a/src/fft.c b/src/fft.c
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+++ b/src/fft.c
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+#include "fft.h"
+#include <math.h>
+#include <stdlib.h>
+
+/* Everything here comes from Audacity 1.3.13
+ (orignally in C++ and with more genericity and functionnality)
+ Original Author : Dominic Mazzoni
+ Licenced under GPL 2.0 (see LICENCE)
+*/
+
+#define MaxFastBits 16
+
+int *gFFTBitTable[MaxFastBits]={NULL};
+
+void InitFFT();
+int NumberOfBitsNeeded(int PowerOfTwo);
+inline int FastReverseBits(int i, int NumBits);
+int ReverseBits(int index, int NumBits);
+
+
+void FFT(int NumSamples,
+ int InverseTransform,
+ float *RealIn, float *ImagIn, float *RealOut, float *ImagOut)
+{
+ int NumBits; /* Number of bits needed to store indices */
+ int i, j, k, n;
+ int BlockSize, BlockEnd;
+
+ double angle_numerator = 2.0 * M_PI;
+ double tr, ti; /* temp real, temp imaginary */
+/*
+ if (!IsPowerOfTwo(NumSamples)) {
+ fprintf(stderr, "%d is not a power of two\n", NumSamples);
+ exit(1);
+ }
+*/
+ if (!gFFTBitTable[0])
+ InitFFT();
+
+ if (!InverseTransform)
+ angle_numerator = -angle_numerator;
+
+ NumBits = NumberOfBitsNeeded(NumSamples);
+
+ /*
+ ** Do simultaneous data copy and bit-reversal ordering into outputs...
+ */
+ for (i = 0; i < NumSamples; i++) {
+ j = FastReverseBits(i, NumBits);
+ RealOut[j] = RealIn[i];
+ ImagOut[j] = (ImagIn == NULL) ? 0.0 : ImagIn[i];
+ }
+
+ /*
+ ** Do the FFT itself...
+ */
+
+ BlockEnd = 1;
+ for (BlockSize = 2; BlockSize <= NumSamples; BlockSize <<= 1) {
+
+ double delta_angle = angle_numerator / (double) BlockSize;
+
+ double sm2 = sin(-2 * delta_angle);
+ double sm1 = sin(-delta_angle);
+ double cm2 = cos(-2 * delta_angle);
+ double cm1 = cos(-delta_angle);
+ double w = 2 * cm1;
+ double ar0, ar1, ar2, ai0, ai1, ai2;
+
+ for (i = 0; i < NumSamples; i += BlockSize) {
+ ar2 = cm2;
+ ar1 = cm1;
+
+ ai2 = sm2;
+ ai1 = sm1;
+
+ for (j = i, n = 0; n < BlockEnd; j++, n++) {
+ ar0 = w * ar1 - ar2;
+ ar2 = ar1;
+ ar1 = ar0;
+
+ ai0 = w * ai1 - ai2;
+ ai2 = ai1;
+ ai1 = ai0;
+
+ k = j + BlockEnd;
+ tr = ar0 * RealOut[k] - ai0 * ImagOut[k];
+ ti = ar0 * ImagOut[k] + ai0 * RealOut[k];
+
+ RealOut[k] = RealOut[j] - tr;
+ ImagOut[k] = ImagOut[j] - ti;
+
+ RealOut[j] += tr;
+ ImagOut[j] += ti;
+ }
+ }
+ BlockEnd = BlockSize;
+ }
+
+ /*
+ ** Need to normalize if inverse transform...
+ */
+
+ if (InverseTransform) {
+ float denom = (float) NumSamples;
+
+ for (i = 0; i < NumSamples; i++) {
+ RealOut[i] /= denom;
+ ImagOut[i] /= denom;
+ }
+ }
+}
+
+void InitFFT() {
+ int len=2;
+ int b, i;
+ for (b=0; b<MaxFastBits; b++) {
+ gFFTBitTable[b]=malloc(len*sizeof(int));
+
+ for (i=0; i<len; i++)
+ gFFTBitTable[b][i] = ReverseBits(i, b+1);
+
+ len <<= 1;
+ }
+}
+
+int NumberOfBitsNeeded(int PowerOfTwo)
+{
+ int i;
+
+/*
+ if (PowerOfTwo < 2) {
+ fprintf(stderr, "Error: FFT called with size %d\n", PowerOfTwo);
+ exit(1);
+ }
+*/
+ for (i = 0;; i++)
+ if (PowerOfTwo & (1 << i))
+ return i;
+}
+
+inline int FastReverseBits(int i, int NumBits)
+{
+ if (NumBits <= MaxFastBits)
+ return gFFTBitTable[NumBits - 1][i];
+ else
+ return ReverseBits(i, NumBits);
+}
+
+int ReverseBits(int index, int NumBits)
+{
+ int i, rev;
+
+ for (i = rev = 0; i < NumBits; i++) {
+ rev = (rev << 1) | (index & 1);
+ index >>= 1;
+ }
+
+ return rev;
+}
+
+
+/*
+ * PowerSpectrum
+ *
+ * This function computes the same as RealFFT, above, but
+ * adds the squares of the real and imaginary part of each
+ * coefficient, extracting the power and throwing away the
+ * phase.
+ *
+ * For speed, it does not call RealFFT, but duplicates some
+ * of its code.
+ */
+
+void PowerSpectrum(float In[PSNumS], float Out[PSHalf]) {
+ int i;
+
+ float theta = M_PI / PSHalf;
+
+ float tmpReal[PSHalf];
+ float tmpImag[PSHalf];
+ float RealOut[PSHalf];
+ float ImagOut[PSHalf];
+
+ for (i=0; i<PSHalf; i++) {
+ tmpReal[i] = In[2*i];
+ tmpImag[i] = In[2*i+1];
+ }
+
+ FFT(PSHalf, 0, tmpReal, tmpImag, RealOut, ImagOut);
+
+ float wtemp = sin(0.5 * theta);
+
+ float wpr = -2.0 * wtemp * wtemp;
+ float wpi = -1.0 * sin(theta);
+ float wr = 1.0 + wpr;
+ float wi = wpi;
+
+ int i3;
+
+ float h1r, h1i, h2r, h2i, rt, it;
+ for (i=1; i < PSHalf/2; i++) {
+
+ i3 = PSHalf - i;
+
+ h1r = 0.5 * (RealOut[i] + RealOut[i3]);
+ h1i = 0.5 * (ImagOut[i] - ImagOut[i3]);
+ h2r = 0.5 * (ImagOut[i] + ImagOut[i3]);
+ h2i = -0.5 * (RealOut[i] - RealOut[i3]);
+
+ rt = h1r + wr * h2r - wi * h2i;
+ it = h1i + wr * h2i + wi * h2r;
+
+ Out[i] = rt * rt + it * it;
+
+ rt = h1r - wr * h2r + wi * h2i;
+ it = -h1i + wr * h2i + wi * h2r;
+
+ Out[i3] = rt * rt + it * it;
+
+ wr = (wtemp = wr) * wpr - wi * wpi + wr;
+ wi = wi * wpr + wtemp * wpi + wi;
+ }
+
+ rt = (h1r = RealOut[0]) + ImagOut[0];
+ it = h1r - ImagOut[0];
+ Out[0] = rt * rt + it * it;
+ rt = RealOut[PSHalf / 2];
+ it = ImagOut[PSHalf / 2];
+ Out[PSHalf / 2] = rt * rt + it * it;
+}
+
+void DeinitFFT() {
+ int i;
+ if (gFFTBitTable[0]) {
+ for (i=0;i<MaxFastBits;i++) {
+ free(gFFTBitTable[i]);
+ }
+ }
+}
+