ref: f14a78d83431facbbe9e350460e8116ef1c66f9e
dir: /src/filterbank.c/
/*
Copyright (C) 2007 Amaury Hazan <ahazan@iua.upf.edu>
and Paul Brossier <piem@piem.org>
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.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/* part of this mfcc implementation were inspired from LibXtract
http://libxtract.sourceforge.net/
*/
#include "aubio_priv.h"
#include "sample.h"
#include "filterbank.h"
#define USE_EQUAL_GAIN 1
#define VERY_SMALL_NUMBER 2e-42
/** \brief A structure to store a set of n_filters filters of lenghts win_s */
struct aubio_filterbank_t_ {
uint_t win_s;
uint_t n_filters;
fvec_t **filters;
};
aubio_filterbank_t * new_aubio_filterbank(uint_t n_filters, uint_t win_s){
/** allocating space for filterbank object */
aubio_filterbank_t * fb = AUBIO_NEW(aubio_filterbank_t);
uint_t filter_cnt;
fb->win_s=win_s;
fb->n_filters=n_filters;
/** allocating filter tables */
fb->filters=AUBIO_ARRAY(fvec_t*,n_filters);
for (filter_cnt=0; filter_cnt<n_filters; filter_cnt++)
/* considering one-channel filters */
fb->filters[filter_cnt]=new_fvec(win_s, 1);
return fb;
}
aubio_filterbank_t * new_aubio_filterbank_mfcc(uint_t n_filters, uint_t win_s, smpl_t samplerate, smpl_t freq_min, smpl_t freq_max){
smpl_t nyquist = samplerate/2.;
uint_t style = 1;
aubio_filterbank_t * fb = new_aubio_filterbank(n_filters, win_s);
uint_t n, i, k, *fft_peak, M, next_peak;
smpl_t norm, mel_freq_max, mel_freq_min, norm_fact, height, inc, val,
freq_bw_mel, *mel_peak, *height_norm, *lin_peak;
mel_peak = height_norm = lin_peak = NULL;
fft_peak = NULL;
norm = 1;
mel_freq_max = 1127 * log(1 + freq_max / 700);
mel_freq_min = 1127 * log(1 + freq_min / 700);
freq_bw_mel = (mel_freq_max - mel_freq_min) / fb->n_filters;
mel_peak = (smpl_t *)malloc((fb->n_filters + 2) * sizeof(smpl_t));
/* +2 for zeros at start and end */
lin_peak = (smpl_t *)malloc((fb->n_filters + 2) * sizeof(smpl_t));
fft_peak = (uint_t *)malloc((fb->n_filters + 2) * sizeof(uint_t));
height_norm = (smpl_t *)malloc(fb->n_filters * sizeof(smpl_t));
if(mel_peak == NULL || height_norm == NULL ||
lin_peak == NULL || fft_peak == NULL)
return NULL;
M = fb->win_s >> 1;
mel_peak[0] = mel_freq_min;
lin_peak[0] = 700 * (exp(mel_peak[0] / 1127) - 1);
fft_peak[0] = lin_peak[0] / nyquist * M;
for (n = 1; n <= fb->n_filters; n++){
/*roll out peak locations - mel, linear and linear on fft window scale */
mel_peak[n] = mel_peak[n - 1] + freq_bw_mel;
lin_peak[n] = 700 * (exp(mel_peak[n] / 1127) -1);
fft_peak[n] = lin_peak[n] / nyquist * M;
}
for (n = 0; n < fb->n_filters; n++){
/*roll out normalised gain of each peak*/
if (style == USE_EQUAL_GAIN){
height = 1;
norm_fact = norm;
}
else{
height = 2 / (lin_peak[n + 2] - lin_peak[n]);
norm_fact = norm / (2 / (lin_peak[2] - lin_peak[0]));
}
height_norm[n] = height * norm_fact;
}
i = 0;
for(n = 0; n < fb->n_filters; n++){
/*calculate the rise increment*/
if(n > 0)
inc = height_norm[n] / (fft_peak[n] - fft_peak[n - 1]);
else
inc = height_norm[n] / fft_peak[n];
val = 0;
/*zero the start of the array*/
for(k = 0; k < i; k++)
//fft_tables[n][k] = 0.f;
fb->filters[n]->data[0][k]=0.f;
/*fill in the rise */
for(; i <= fft_peak[n]; i++){
// fft_tables[n][i] = val;
fb->filters[n]->data[0][k]=val;
val += inc;
}
/*calculate the fall increment */
inc = height_norm[n] / (fft_peak[n + 1] - fft_peak[n]);
val = 0;
next_peak = fft_peak[n + 1];
/*reverse fill the 'fall' */
for(i = next_peak; i > fft_peak[n]; i--){
//fft_tables[n][i] = val;
fb->filters[n]->data[0][k]=val;
val += inc;
}
/*zero the rest of the array*/
for(k = next_peak + 1; k < fb->win_s; k++)
//fft_tables[n][k] = 0.f;
fb->filters[n]->data[0][k]=0.f;
}
free(mel_peak);
free(lin_peak);
free(height_norm);
free(fft_peak);
return fb;
}
void del_aubio_filterbank(aubio_filterbank_t * fb){
uint_t filter_cnt;
/** deleting filter tables first */
for (filter_cnt=0; filter_cnt<fb->n_filters; filter_cnt++)
del_fvec(fb->filters[filter_cnt]);
AUBIO_FREE(fb->filters);
AUBIO_FREE(fb);
}
void aubio_filterbank_do(aubio_filterbank_t * f, cvec_t * in, fvec_t *out) {
uint_t n, filter_cnt;
for(filter_cnt = 0; (filter_cnt < f->n_filters)
&& (filter_cnt < out->length); filter_cnt++){
out->data[0][filter_cnt] = 0.f;
for(n = 0; n < in->length; n++){
out->data[0][filter_cnt] += in->norm[0][n]
* f->filters[filter_cnt]->data[0][n];
}
out->data[0][filter_cnt] =
LOG(out->data[0][filter_cnt] < VERY_SMALL_NUMBER ?
VERY_SMALL_NUMBER : out->data[0][filter_cnt]);
}
return;
}