libs/qm-dsp/dsp/phasevocoder/PhaseVocoder.cpp

   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.
   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 <math.h>
  19
  20 //////////////////////////////////////////////////////////////////////
  21 // Construction/Destruction
  22 //////////////////////////////////////////////////////////////////////
  23
  24 PhaseVocoder::PhaseVocoder(unsigned int n) :
  25     m_n(n)
  26 {
  27     m_fft = new FFTReal(m_n);
  28     m_realOut = new double[m_n];
  29     m_imagOut = new double[m_n];
  30 }
  31
  32 PhaseVocoder::~PhaseVocoder()
  33 {
  34     delete [] m_realOut;
  35     delete [] m_imagOut;
  36     delete m_fft;
  37 }
  38
  39 void PhaseVocoder::FFTShift(unsigned int size, double *src)
  40 {
  41     const int hs = size/2;
  42     for (int i = 0; i < hs; ++i) {
  43         double tmp = src[i];
  44         src[i] = src[i + hs];
  45         src[i + hs] = tmp;
  46     }
  47 }
  48
  49 void PhaseVocoder::process(double *src, double *mag, double *theta)
  50 {
  51     FFTShift( m_n, src);
  52
  53     m_fft->process(0, src, m_realOut, m_imagOut);
  54
  55     getMagnitude( m_n/2, mag, m_realOut, m_imagOut);
  56     getPhase( m_n/2, theta, m_realOut, m_imagOut);
  57 }
  58
  59 void PhaseVocoder::getMagnitude(unsigned int size, double *mag, double *real, double *imag)
  60 {
  61     unsigned int j;
  62
  63     for( j = 0; j < size; j++)
  64     {
  65         mag[ j ] = sqrt( real[ j ] * real[ j ] + imag[ j ] * imag[ j ]);
  66     }
  67 }
  68
  69 void PhaseVocoder::getPhase(unsigned int size, double *theta, double *real, double *imag)
  70 {
  71     unsigned int k;
  72
  73     // Phase Angle "matlab" style
  74     //Watch out for quadrant mapping  !!!
  75     for( k = 0; k < size; k++)
  76     {
  77         theta[ k ] = atan2( -imag[ k ], real[ k ]);
  78     }
  79 }