165 lines
4.0 KiB
C++
165 lines
4.0 KiB
C++
/**********************************************************************
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Audacity: A Digital Audio Editor
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Spectrum.cpp
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Dominic Mazzoni
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*******************************************************************//*!
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\file Spectrum.cpp
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\brief Functions for computing Spectra.
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*//*******************************************************************/
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#include <math.h>
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#include "Spectrum.h"
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#include "FFT.h"
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#if 1 //(UGLY_IEEE754_FLOAT32_HACK :-)
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static inline float todB_a(const float *x){
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return (float)((*(wxInt32 *)x)&0x7fffffff) * 7.17711438e-7f -764.6161886f;
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}
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#else
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static inline float todB_a(const float *x){
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return (*(x)==0?-400.f:logf(*(x)**(x))*4.34294480f);
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}
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#endif
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bool ComputeSpectrum(float * data, int width,
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int windowSize,
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double rate, float *output,
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bool autocorrelation, int windowFunc)
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{
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if (width < windowSize)
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return false;
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if (!data || !output)
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return true;
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float *processed = new float[windowSize];
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int i;
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for (i = 0; i < windowSize; i++)
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processed[i] = float(0.0);
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int half = windowSize / 2;
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float *in = new float[windowSize];
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float *out = new float[windowSize];
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float *out2 = new float[windowSize];
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int start = 0;
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int windows = 0;
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while (start + windowSize <= width) {
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for (i = 0; i < windowSize; i++)
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in[i] = data[start + i];
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WindowFunc(windowFunc, windowSize, in);
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if (autocorrelation) {
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// Take FFT
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#ifdef EXPERIMENTAL_USE_REALFFTF
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RealFFT(windowSize, in, out, out2);
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#else
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FFT(windowSize, false, in, NULL, out, out2);
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#endif
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// Compute power
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for (i = 0; i < windowSize; i++)
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in[i] = (out[i] * out[i]) + (out2[i] * out2[i]);
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// Tolonen and Karjalainen recommend taking the cube root
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// of the power, instead of the square root
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for (i = 0; i < windowSize; i++)
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in[i] = powf(in[i], 1.0f / 3.0f);
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// Take FFT
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#ifdef EXPERIMENTAL_USE_REALFFTF
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RealFFT(windowSize, in, out, out2);
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#else
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FFT(windowSize, false, in, NULL, out, out2);
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#endif
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}
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else
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PowerSpectrum(windowSize, in, out);
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// Take real part of result
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for (i = 0; i < half; i++)
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processed[i] += out[i];
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start += half;
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windows++;
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}
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if (autocorrelation) {
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// Peak Pruning as described by Tolonen and Karjalainen, 2000
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/*
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Combine most of the calculations in a single for loop.
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It should be safe, as indexes refer only to current and previous elements,
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that have already been clipped, etc...
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*/
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for (i = 0; i < half; i++) {
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// Clip at zero, copy to temp array
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if (processed[i] < 0.0)
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processed[i] = float(0.0);
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out[i] = processed[i];
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// Subtract a time-doubled signal (linearly interp.) from the original
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// (clipped) signal
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if ((i % 2) == 0)
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processed[i] -= out[i / 2];
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else
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processed[i] -= ((out[i / 2] + out[i / 2 + 1]) / 2);
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// Clip at zero again
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if (processed[i] < 0.0)
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processed[i] = float(0.0);
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}
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// Reverse and scale
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for (i = 0; i < half; i++)
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in[i] = processed[i] / (windowSize / 4);
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for (i = 0; i < half; i++)
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processed[half - 1 - i] = in[i];
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} else {
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// Convert to decibels
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// But do it safely; -Inf is nobody's friend
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for (i = 0; i < half; i++){
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float temp=(processed[i] / windowSize / windows);
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if (temp > 0.0)
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processed[i] = 10*log10(temp);
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else
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processed[i] = 0;
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}
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}
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for(i=0;i<half;i++)
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output[i] = processed[i];
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delete[]in;
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delete[]out;
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delete[]out2;
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delete[]processed;
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return true;
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}
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// Indentation settings for Vim and Emacs and unique identifier for Arch, a
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// version control system. Please do not modify past this point.
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//
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// Local Variables:
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// c-basic-offset: 3
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// indent-tabs-mode: nil
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// End:
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//
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// vim: et sts=3 sw=3
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// arch-tag: 29527ca5-00d0-442d-afde-d699aee29a31
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