ref: 5c4ec3cb6b9cafcc5a953f2176c6069ed02fe4e2
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 "fvec.h"
#include "cvec.h"
#include "spectral/filterbank.h"
#include "mathutils.h"
void
aubio_filterbank_set_mel_coeffs (aubio_filterbank_t * fb, fvec_t * freqs,
smpl_t samplerate)
{
fvec_t *filters = aubio_filterbank_get_coeffs (fb);
uint_t n_filters = filters->channels, win_s = filters->length;
uint_t fn; /* filter counter */
uint_t bin; /* bin counter */
/* 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);
}
/* convenience reference to lower/center/upper frequency for each triangle */
fvec_t *lower_freqs = new_fvec (n_filters, 1);
fvec_t *upper_freqs = new_fvec (n_filters, 1);
fvec_t *center_freqs = new_fvec (n_filters, 1);
/* height of each triangle */
fvec_t *triangle_heights = new_fvec (n_filters, 1);
/* lookup table of each bin frequency in hz */
fvec_t *fft_freqs = new_fvec (win_s, 1);
/* fill up the lower/center/upper */
for (fn = 0; fn < n_filters; fn++) {
lower_freqs->data[0][fn] = freqs->data[0][fn];
center_freqs->data[0][fn] = freqs->data[0][fn + 1];
upper_freqs->data[0][fn] = freqs->data[0][fn + 2];
}
/* compute triangle heights so that each triangle has unit area */
for (fn = 0; fn < n_filters; fn++) {
triangle_heights->data[0][fn] =
2. / (upper_freqs->data[0][fn] - lower_freqs->data[0][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[0][bin] = aubio_bintofreq (bin, samplerate, (win_s - 1) * 2);
}
/* zeroing of all filters */
fvec_zeros (filters);
/* 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[0][bin] <= lower_freqs->data[0][fn] &&
fft_freqs->data[0][bin + 1] > lower_freqs->data[0][fn]) {
break;
}
}
bin++;
/* compute positive slope step size */
smpl_t riseInc =
triangle_heights->data[0][fn] /
(center_freqs->data[0][fn] - lower_freqs->data[0][fn]);
/* compute coefficients in positive slope */
for (; bin < win_s - 1; bin++) {
filters->data[fn][bin] =
(fft_freqs->data[0][bin] - lower_freqs->data[0][fn]) * riseInc;
if (fft_freqs->data[0][bin + 1] > center_freqs->data[0][fn])
break;
}
bin++;
/* compute negative slope step size */
smpl_t downInc =
triangle_heights->data[0][fn] /
(upper_freqs->data[0][fn] - center_freqs->data[0][fn]);
/* compute coefficents in negative slope */
for (; bin < win_s - 1; bin++) {
filters->data[fn][bin] +=
(upper_freqs->data[0][fn] - fft_freqs->data[0][bin]) * downInc;
if (fft_freqs->data[0][bin + 1] > upper_freqs->data[0][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);
}
void
aubio_filterbank_set_mel_coeffs_slaney (aubio_filterbank_t * fb,
smpl_t samplerate)
{
/* 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 */
/* buffers to compute filter frequencies */
fvec_t *freqs = new_fvec (n_filters + 2, 1);
/* first step: fill all the linear filter frequencies */
for (fn = 0; fn < linearFilters; fn++) {
freqs->data[0][fn] = lowestFrequency + fn * linearSpacing;
}
smpl_t lastlinearCF = freqs->data[0][fn - 1];
/* second step: fill all the log filter frequencies */
for (fn = 0; fn < logFilters + 2; fn++) {
freqs->data[0][fn + linearFilters] =
lastlinearCF * (POW (logSpacing, fn + 1));
}
/* now compute the actual coefficients */
aubio_filterbank_set_mel_coeffs (fb, freqs, samplerate);
/* destroy vector used to store frequency limits */
del_fvec (freqs);
}