mirror of
https://github.com/cookiengineer/audacity
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6c57948d8f
... Unnecessary because transitively included. But each .cpp file still includes its own .h file near the top to ensure that it compiles indenendently, even if it is reincluded transitively later.
126 lines
3.3 KiB
C++
126 lines
3.3 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 "Spectrum.h"
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#include <math.h>
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#include "SampleFormat.h"
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bool ComputeSpectrum(const float * data, size_t width,
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size_t windowSize,
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double WXUNUSED(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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Floats processed{ windowSize };
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for (size_t i = 0; i < windowSize; i++)
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processed[i] = float(0.0);
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auto half = windowSize / 2;
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Floats in{ windowSize };
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Floats out{ windowSize };
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Floats out2{ windowSize };
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size_t start = 0;
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unsigned windows = 0;
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while (start + windowSize <= width) {
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for (size_t i = 0; i < windowSize; i++)
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in[i] = data[start + i];
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WindowFunc(windowFunc, windowSize, in.get());
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if (autocorrelation) {
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// Take FFT
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RealFFT(windowSize, in.get(), out.get(), out2.get());
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// Compute power
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for (size_t 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 (size_t 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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RealFFT(windowSize, in.get(), out.get(), out2.get());
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}
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else
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PowerSpectrum(windowSize, in.get(), out.get());
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// Take real part of result
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for (size_t 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 (size_t 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 (size_t i = 0; i < half; i++)
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in[i] = processed[i] / (windowSize / 4);
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for (size_t 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 (size_t 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(size_t i = 0; i < half; i++)
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output[i] = processed[i];
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return true;
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}
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