ref: 9c59a30694782fe175fee5c54f2d008e9fbf489d
dir: /src/spectral/filterbank_mel.c/
/*
Copyright (C) 2007-2009 Paul Brossier <piem@aubio.org>
and Amaury Hazan <ahazan@iua.upf.edu>
This file is part of aubio.
aubio 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 3 of the License, or
(at your option) any later version.
aubio 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 aubio. If not, see <http://www.gnu.org/licenses/>.
*/
#include "aubio_priv.h"
#include "fmat.h"
#include "fvec.h"
#include "cvec.h"
#include "spectral/filterbank.h"
#include "spectral/filterbank_mel.h"
#include "mathutils.h"
uint_t
aubio_filterbank_set_triangle_bands (aubio_filterbank_t * fb,
const fvec_t * freqs, smpl_t samplerate)
{
fmat_t *filters = aubio_filterbank_get_coeffs (fb);
uint_t n_filters = filters->height, win_s = filters->length;
fvec_t *lower_freqs, *upper_freqs, *center_freqs;
fvec_t *triangle_heights, *fft_freqs;
uint_t fn; /* filter counter */
uint_t bin; /* bin counter */
smpl_t riseInc, downInc;
/* freqs define the bands of triangular overlapping windows.
throw a warning if filterbank object fb is too short. */
if (freqs->length - 2 > n_filters) {
AUBIO_WRN ("not enough filters, %d allocated but %d requested\n",
n_filters, freqs->length - 2);
}
if (freqs->length - 2 < n_filters) {
AUBIO_WRN ("too many filters, %d allocated but %d requested\n",
n_filters, freqs->length - 2);
}
if (freqs->data[freqs->length - 1] > samplerate / 2) {
AUBIO_WRN ("Nyquist frequency is %fHz, but highest frequency band ends at \
%fHz\n", samplerate / 2, freqs->data[freqs->length - 1]);
}
/* convenience reference to lower/center/upper frequency for each triangle */
lower_freqs = new_fvec (n_filters);
upper_freqs = new_fvec (n_filters);
center_freqs = new_fvec (n_filters);
/* height of each triangle */
triangle_heights = new_fvec (n_filters);
/* lookup table of each bin frequency in hz */
fft_freqs = new_fvec (win_s);
/* fill up the lower/center/upper */
for (fn = 0; fn < n_filters; fn++) {
lower_freqs->data[fn] = freqs->data[fn];
center_freqs->data[fn] = freqs->data[fn + 1];
upper_freqs->data[fn] = freqs->data[fn + 2];
}
/* compute triangle heights so that each triangle has unit area */
for (fn = 0; fn < n_filters; fn++) {
triangle_heights->data[fn] =
2. / (upper_freqs->data[fn] - lower_freqs->data[fn]);
}
/* fill fft_freqs lookup table, which assigns the frequency in hz to each bin */
for (bin = 0; bin < win_s; bin++) {
fft_freqs->data[bin] =
aubio_bintofreq (bin, samplerate, (win_s - 1) * 2);
}
/* zeroing of all filters */
fmat_zeros (filters);
if (fft_freqs->data[1] >= lower_freqs->data[0]) {
/* - 1 to make sure we don't miss the smallest power of two */
uint_t min_win_s =
(uint_t) FLOOR (samplerate / lower_freqs->data[0]) - 1;
AUBIO_WRN ("Lowest frequency bin (%.2fHz) is higher than lowest frequency \
band (%.2f-%.2fHz). Consider increasing the window size from %d to %d.\n",
fft_freqs->data[1], lower_freqs->data[0],
upper_freqs->data[0], (win_s - 1) * 2,
aubio_next_power_of_two (min_win_s));
}
/* building each filter table */
for (fn = 0; fn < n_filters; fn++) {
/* skip first elements */
for (bin = 0; bin < win_s - 1; bin++) {
if (fft_freqs->data[bin] <= lower_freqs->data[fn] &&
fft_freqs->data[bin + 1] > lower_freqs->data[fn]) {
bin++;
break;
}
}
/* compute positive slope step size */
riseInc =
triangle_heights->data[fn] /
(center_freqs->data[fn] - lower_freqs->data[fn]);
/* compute coefficients in positive slope */
for (; bin < win_s - 1; bin++) {
filters->data[fn][bin] =
(fft_freqs->data[bin] - lower_freqs->data[fn]) * riseInc;
if (fft_freqs->data[bin + 1] >= center_freqs->data[fn]) {
bin++;
break;
}
}
/* compute negative slope step size */
downInc =
triangle_heights->data[fn] /
(upper_freqs->data[fn] - center_freqs->data[fn]);
/* compute coefficents in negative slope */
for (; bin < win_s - 1; bin++) {
filters->data[fn][bin] +=
(upper_freqs->data[fn] - fft_freqs->data[bin]) * downInc;
if (filters->data[fn][bin] < 0.) {
filters->data[fn][bin] = 0.;
}
if (fft_freqs->data[bin + 1] >= upper_freqs->data[fn])
break;
}
/* nothing else to do */
}
/* destroy temporarly allocated vectors */
del_fvec (lower_freqs);
del_fvec (upper_freqs);
del_fvec (center_freqs);
del_fvec (triangle_heights);
del_fvec (fft_freqs);
return 0;
}
uint_t
aubio_filterbank_set_mel_coeffs_slaney (aubio_filterbank_t * fb,
smpl_t samplerate)
{
uint_t retval;
/* Malcolm Slaney parameters */
smpl_t lowestFrequency = 133.3333;
smpl_t linearSpacing = 66.66666666;
smpl_t logSpacing = 1.0711703;
uint_t linearFilters = 13;
uint_t logFilters = 27;
uint_t n_filters = linearFilters + logFilters;
uint_t fn; /* filter counter */
smpl_t lastlinearCF;
/* buffers to compute filter frequencies */
fvec_t *freqs = new_fvec (n_filters + 2);
/* first step: fill all the linear filter frequencies */
for (fn = 0; fn < linearFilters; fn++) {
freqs->data[fn] = lowestFrequency + fn * linearSpacing;
}
lastlinearCF = freqs->data[fn - 1];
/* second step: fill all the log filter frequencies */
for (fn = 0; fn < logFilters + 2; fn++) {
freqs->data[fn + linearFilters] =
lastlinearCF * (POW (logSpacing, fn + 1));
}
/* now compute the actual coefficients */
retval = aubio_filterbank_set_triangle_bands (fb, freqs, samplerate);
/* destroy vector used to store frequency limits */
del_fvec (freqs);
return retval;
}