gtk2_ardour/fft.cc

   1 /*
   2     Copyright (C) 2008 Paul Davis
   3     Author: Sampo Savolainen
   4
   5     This program is free software; you can redistribute it and/or modify
   6     it under the terms of the GNU General Public License as published by
   7     the Free Software Foundation; either version 2 of the License, or
   8     (at your option) any later version.
   9
  10     This program is distributed in the hope that it will be useful,
  11     but WITHOUT ANY WARRANTY; without even the implied warranty of
  12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13     GNU General Public License for more details.
  14
  15     You should have received a copy of the GNU General Public License
  16     along with this program; if not, write to the Free Software
  17     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  18
  19 */
  20 #include "fft.h"
  21
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <math.h>
  25
  26 using namespace GTKArdour;
  27
  28 FFT::FFT(uint32_t windowSize)
  29         : _window_size(windowSize),
  30           _data_size(_window_size/2),
  31         _iterations(0),
  32         _hann_window(0)
  33 {
  34         _fftInput  = (float *) fftwf_malloc(sizeof(float) * _window_size);
  35
  36         _fftOutput = (float *) fftwf_malloc(sizeof(float) * _window_size);
  37
  38         _power_at_bin  = (float *) malloc(sizeof(float) * _data_size);
  39         _phase_at_bin  = (float *) malloc(sizeof(float) * _data_size);
  40
  41         _plan = fftwf_plan_r2r_1d(_window_size, _fftInput, _fftOutput, FFTW_R2HC, FFTW_ESTIMATE);
  42
  43         reset();
  44 }
  45
  46 void
  47 FFT::reset()
  48 {
  49         memset(_power_at_bin, 0, sizeof(float) * _data_size);
  50         memset(_phase_at_bin, 0, sizeof(float) * _data_size);
  51
  52         _iterations = 0;
  53 }
  54
  55 void
  56 FFT::analyze(ARDOUR::Sample *input, WindowingType windowing_type)
  57 {
  58         _iterations++;
  59
  60         memcpy(_fftInput, input, sizeof(float) * _window_size);
  61
  62         if (windowing_type == HANN) {
  63                 float *window = get_hann_window();
  64                 for (uint32_t i = 0; i < _window_size; i++) {
  65                         _fftInput[i] *= window[i];
  66                 }
  67         }
  68
  69         fftwf_execute(_plan);
  70
  71         _power_at_bin[0] += _fftOutput[0] * _fftOutput[0];
  72         _phase_at_bin[0] += 0.0;
  73
  74         float power;
  75         float phase;
  76
  77 #define Re (_fftOutput[i])
  78 #define Im (_fftOutput[_window_size-i])
  79         for (uint32_t i=1; i < _data_size - 1; i++) {
  80
  81                 power = (Re * Re) + (Im * Im);
  82                 phase = atanf(Im / Re);
  83
  84                 if (Re < 0.0 && Im > 0.0) {
  85                         phase += M_PI;
  86                 } else if (Re < 0.0 && Im < 0.0) {
  87                         phase -= M_PI;
  88                 }
  89
  90                 _power_at_bin[i] += power;
  91                 _phase_at_bin[i] += phase;
  92         }
  93 #undef Re
  94 #undef Im
  95 }
  96
  97 void
  98 FFT::calculate()
  99 {
 100         if (_iterations > 1) {
 101                 for (uint32_t i=0; i < _data_size - 1; i++) {
 102                         _power_at_bin[i] /= (float)_iterations;
 103                         _phase_at_bin[i] /= (float)_iterations;
 104                 }
 105                 _iterations = 1;
 106         }
 107 }
 108
 109 float *
 110 FFT::get_hann_window()
 111 {
 112         if (_hann_window)
 113                 return _hann_window;
 114
 115
 116         _hann_window = (float *) malloc(sizeof(float) * _window_size);
 117
 118         double sum = 0.0;
 119
 120         for (uint32_t i=0; i < _window_size; i++) {
 121                 _hann_window[i]=0.81f * ( 0.5f - (0.5f * (float) cos(2.0f * M_PI * (float)i / (float)(_window_size))));
 122                 sum += _hann_window[i];
 123         }
 124
 125         double isum = 1.0 / sum;
 126
 127         for (uint32_t i=0; i < _window_size; i++) {
 128                 _hann_window[i] *= isum;
 129         }
 130
 131         return _hann_window;
 132 }
 133
 134
 135 FFT::~FFT()
 136 {
 137         if (_hann_window) {
 138                 free(_hann_window);
 139         }
 140         fftwf_destroy_plan(_plan);
 141         free(_power_at_bin);
 142         free(_phase_at_bin);
 143         free(_fftOutput);
 144         free(_fftInput);
 145 }