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 FFT::FFT(uint32_t windowSize)
  27         : _window_size(windowSize),
  28           _data_size(_window_size/2),
  29         _iterations(0),
  30         _hann_window(0)
  31 {
  32         _fftInput  = (float *) fftwf_malloc(sizeof(float) * _window_size);
  33
  34         _fftOutput = (float *) fftwf_malloc(sizeof(float) * _window_size);
  35
  36         _power_at_bin  = (float *) malloc(sizeof(float) * _data_size);
  37         _phase_at_bin  = (float *) malloc(sizeof(float) * _data_size);
  38
  39         _plan = fftwf_plan_r2r_1d(_window_size, _fftInput, _fftOutput, FFTW_R2HC, FFTW_ESTIMATE);
  40
  41         reset();
  42 }
  43
  44 void
  45 FFT::reset()
  46 {
  47         memset(_power_at_bin, 0, sizeof(float) * _data_size);
  48         memset(_phase_at_bin, 0, sizeof(float) * _data_size);
  49
  50         _iterations = 0;
  51 }
  52
  53 void
  54 FFT::analyze(ARDOUR::Sample *input, WindowingType windowing_type)
  55 {
  56         _iterations++;
  57
  58         memcpy(_fftInput, input, sizeof(float) * _window_size);
  59
  60         if (windowing_type == HANN) {
  61                 float *window = get_hann_window();
  62                 for (uint32_t i = 0; i < _window_size; i++) {
  63                         _fftInput[i] *= window[i];
  64                 }
  65         }
  66
  67         fftwf_execute(_plan);
  68
  69         _power_at_bin[0] += _fftOutput[0] * _fftOutput[0];
  70         _phase_at_bin[0] += 0.0;
  71
  72         float power;
  73         float phase;
  74
  75 #define Re (_fftOutput[i])
  76 #define Im (_fftOutput[_window_size-i])
  77         for (uint32_t i=1; i < _data_size - 1; i++) {
  78
  79                 power = (Re * Re) + (Im * Im);
  80                 phase = atanf(Im / Re);
  81
  82                 if (Re < 0.0 && Im > 0.0) {
  83                         phase += M_PI;
  84                 } else if (Re < 0.0 && Im < 0.0) {
  85                         phase -= M_PI;
  86                 }
  87
  88                 _power_at_bin[i] += power;
  89                 _phase_at_bin[i] += phase;
  90         }
  91 #undef Re
  92 #undef Im
  93 }
  94
  95 void
  96 FFT::calculate()
  97 {
  98         if (_iterations > 1) {
  99                 for (uint32_t i=0; i < _data_size - 1; i++) {
 100                         _power_at_bin[i] /= (float)_iterations;
 101                         _phase_at_bin[i] /= (float)_iterations;
 102                 }
 103                 _iterations = 1;
 104         }
 105 }
 106
 107 float *
 108 FFT::get_hann_window()
 109 {
 110         if (_hann_window)
 111                 return _hann_window;
 112
 113
 114         _hann_window = (float *) malloc(sizeof(float) * _window_size);
 115
 116         double sum = 0.0;
 117
 118         for (uint32_t i=0; i < _window_size; i++) {
 119                 _hann_window[i]=0.81f * ( 0.5f - (0.5f * (float) cos(2.0f * M_PI * (float)i / (float)(_window_size))));
 120                 sum += _hann_window[i];
 121         }
 122
 123         double isum = 1.0 / sum;
 124
 125         for (uint32_t i=0; i < _window_size; i++) {
 126                 _hann_window[i] *= isum;
 127         }
 128
 129         return _hann_window;
 130 }
 131
 132
 133 FFT::~FFT()
 134 {
 135         if (_hann_window) {
 136                 free(_hann_window);
 137         }
 138         fftwf_destroy_plan(_plan);
 139         free(_power_at_bin);
 140         free(_phase_at_bin);
 141         free(_fftOutput);
 142         free(_fftInput);
 143 }