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/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*- vi:set ts=8 sts=4 sw=4: */
/*
QM DSP Library
Centre for Digital Music, Queen Mary, University of London.
This file 2005-2006 Christian Landone, copyright 2013 QMUL.
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version. See the file
COPYING included with this distribution for more information.
*/
#include "PhaseVocoder.h"
#include "dsp/transforms/FFT.h"
#include "maths/MathUtilities.h"
#include <math.h>
#include <cassert>
#include <iostream>
using std::cerr;
using std::endl;
PhaseVocoder::PhaseVocoder(int n, int hop) :
m_n(n),
m_hop(hop)
{
m_fft = new FFTReal(m_n);
m_time = new double[m_n];
m_real = new double[m_n];
m_imag = new double[m_n];
m_phase = new double[m_n/2 + 1];
m_unwrapped = new double[m_n/2 + 1];
for (int i = 0; i < m_n/2 + 1; ++i) {
m_phase[i] = 0.0;
m_unwrapped[i] = 0.0;
}
reset();
}
PhaseVocoder::~PhaseVocoder()
{
delete[] m_unwrapped;
delete[] m_phase;
delete[] m_real;
delete[] m_imag;
delete[] m_time;
delete m_fft;
}
void PhaseVocoder::FFTShift(double *src)
{
const int hs = m_n/2;
for (int i = 0; i < hs; ++i) {
double tmp = src[i];
src[i] = src[i + hs];
src[i + hs] = tmp;
}
}
void PhaseVocoder::processTimeDomain(const double *src,
double *mag, double *theta,
double *unwrapped)
{
for (int i = 0; i < m_n; ++i) {
m_time[i] = src[i];
}
FFTShift(m_time);
m_fft->forward(m_time, m_real, m_imag);
getMagnitudes(mag);
getPhases(theta);
unwrapPhases(theta, unwrapped);
}
void PhaseVocoder::processFrequencyDomain(const double *reals,
const double *imags,
double *mag, double *theta,
double *unwrapped)
{
for (int i = 0; i < m_n/2 + 1; ++i) {
m_real[i] = reals[i];
m_imag[i] = imags[i];
}
getMagnitudes(mag);
getPhases(theta);
unwrapPhases(theta, unwrapped);
}
void PhaseVocoder::reset()
{
for (int i = 0; i < m_n/2 + 1; ++i) {
// m_phase stores the "previous" phase, so set to one step
// behind so that a signal with initial phase at zero matches
// the expected values. This is completely unnecessary for any
// analytical purpose, it's just tidier.
double omega = (2 * M_PI * m_hop * i) / m_n;
m_phase[i] = -omega;
m_unwrapped[i] = -omega;
}
}
void PhaseVocoder::getMagnitudes(double *mag)
{
for (int i = 0; i < m_n/2 + 1; i++) {
mag[i] = sqrt(m_real[i] * m_real[i] + m_imag[i] * m_imag[i]);
}
}
void PhaseVocoder::getPhases(double *theta)
{
for (int i = 0; i < m_n/2 + 1; i++) {
theta[i] = atan2(m_imag[i], m_real[i]);
}
}
void PhaseVocoder::unwrapPhases(double *theta, double *unwrapped)
{
for (int i = 0; i < m_n/2 + 1; ++i) {
double omega = (2 * M_PI * m_hop * i) / m_n;
double expected = m_phase[i] + omega;
double error = MathUtilities::princarg(theta[i] - expected);
unwrapped[i] = m_unwrapped[i] + omega + error;
m_phase[i] = theta[i];
m_unwrapped[i] = unwrapped[i];
}
}
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