1 /* -*- c-basic-offset: 4 indent-tabs-mode: nil -*- vi:set ts=8 sts=4 sw=4: */
2
3 /*
4 QM DSP Library
5
6 Centre for Digital Music, Queen Mary, University of London.
7 This file 2005-2006 Christian Landone, copyright 2013 QMUL.
8
9 This program is free software; you can redistribute it and/or
10 modify it under the terms of the GNU General Public License as
11 published by the Free Software Foundation; either version 2 of the
12 License, or (at your option) any later version. See the file
13 COPYING included with this distribution for more information.
14 */
15
16 #include "PhaseVocoder.h"
17 #include "dsp/transforms/FFT.h"
18 #include "maths/MathUtilities.h"
19 #include <math.h>
20
21 #include <cassert>
22
23 #include <iostream>
24 using std::cerr;
25 using std::endl;
26
PhaseVocoder(int n,int hop)27 PhaseVocoder::PhaseVocoder(int n, int hop) :
28 m_n(n),
29 m_hop(hop)
30 {
31 m_fft = new FFTReal(m_n);
32 m_time = new double[m_n];
33 m_real = new double[m_n];
34 m_imag = new double[m_n];
35 m_phase = new double[m_n/2 + 1];
36 m_unwrapped = new double[m_n/2 + 1];
37
38 for (int i = 0; i < m_n/2 + 1; ++i) {
39 m_phase[i] = 0.0;
40 m_unwrapped[i] = 0.0;
41 }
42
43 reset();
44 }
45
~PhaseVocoder()46 PhaseVocoder::~PhaseVocoder()
47 {
48 delete[] m_unwrapped;
49 delete[] m_phase;
50 delete[] m_real;
51 delete[] m_imag;
52 delete[] m_time;
53 delete m_fft;
54 }
55
FFTShift(double * src)56 void PhaseVocoder::FFTShift(double *src)
57 {
58 const int hs = m_n/2;
59 for (int i = 0; i < hs; ++i) {
60 double tmp = src[i];
61 src[i] = src[i + hs];
62 src[i + hs] = tmp;
63 }
64 }
65
processTimeDomain(const double * src,double * mag,double * theta,double * unwrapped)66 void PhaseVocoder::processTimeDomain(const double *src,
67 double *mag, double *theta,
68 double *unwrapped)
69 {
70 for (int i = 0; i < m_n; ++i) {
71 m_time[i] = src[i];
72 }
73 FFTShift(m_time);
74 m_fft->forward(m_time, m_real, m_imag);
75 getMagnitudes(mag);
76 getPhases(theta);
77 unwrapPhases(theta, unwrapped);
78 }
79
processFrequencyDomain(const double * reals,const double * imags,double * mag,double * theta,double * unwrapped)80 void PhaseVocoder::processFrequencyDomain(const double *reals,
81 const double *imags,
82 double *mag, double *theta,
83 double *unwrapped)
84 {
85 for (int i = 0; i < m_n/2 + 1; ++i) {
86 m_real[i] = reals[i];
87 m_imag[i] = imags[i];
88 }
89 getMagnitudes(mag);
90 getPhases(theta);
91 unwrapPhases(theta, unwrapped);
92 }
93
reset()94 void PhaseVocoder::reset()
95 {
96 for (int i = 0; i < m_n/2 + 1; ++i) {
97 // m_phase stores the "previous" phase, so set to one step
98 // behind so that a signal with initial phase at zero matches
99 // the expected values. This is completely unnecessary for any
100 // analytical purpose, it's just tidier.
101 double omega = (2 * M_PI * m_hop * i) / m_n;
102 m_phase[i] = -omega;
103 m_unwrapped[i] = -omega;
104 }
105 }
106
getMagnitudes(double * mag)107 void PhaseVocoder::getMagnitudes(double *mag)
108 {
109 for (int i = 0; i < m_n/2 + 1; i++) {
110 mag[i] = sqrt(m_real[i] * m_real[i] + m_imag[i] * m_imag[i]);
111 }
112 }
113
getPhases(double * theta)114 void PhaseVocoder::getPhases(double *theta)
115 {
116 for (int i = 0; i < m_n/2 + 1; i++) {
117 theta[i] = atan2(m_imag[i], m_real[i]);
118 }
119 }
120
unwrapPhases(double * theta,double * unwrapped)121 void PhaseVocoder::unwrapPhases(double *theta, double *unwrapped)
122 {
123 for (int i = 0; i < m_n/2 + 1; ++i) {
124
125 double omega = (2 * M_PI * m_hop * i) / m_n;
126 double expected = m_phase[i] + omega;
127 double error = MathUtilities::princarg(theta[i] - expected);
128
129 unwrapped[i] = m_unwrapped[i] + omega + error;
130
131 m_phase[i] = theta[i];
132 m_unwrapped[i] = unwrapped[i];
133 }
134 }
135
136