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#
# Copyright (C) 2016-2019 by Nathan Lovato, Daniel Oakey, Razvan Radulescu, and contributors
#
# This file is part of Power Sequencer.
#
# Power Sequencer 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.
#
# Power Sequencer 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 Power Sequencer. If
# not, see <https://www.gnu.org/licenses/>.
#
import numpy as np
def trfbank(fs, nfft, lowfreq, linsc, logsc, nlinfilt, nlogfilt):
"""Compute triangular filterbank for MFCC computation."""
# Total number of filters
nfilt = nlinfilt + nlogfilt
# ------------------------
# Compute the filter bank
# ------------------------
# Compute start/middle/end points of the triangular filters in spectral
# domain
freqs = np.zeros(nfilt + 2)
freqs[:nlinfilt] = lowfreq + np.arange(nlinfilt) * linsc
freqs[nlinfilt:] = freqs[nlinfilt - 1] * logsc ** np.arange(1, nlogfilt + 3)
heights = 2.0 / (freqs[2:] - freqs[0:-2])
# Compute filterbank coeff (in fft domain, in bins)
fbank = np.zeros((nfilt, nfft))
# FFT bins (in Hz)
nfreqs = np.arange(nfft) / (1.0 * nfft) * fs
for i in range(nfilt):
low = freqs[i]
cen = freqs[i + 1]
hi = freqs[i + 2]
lid = np.arange(np.floor(low * nfft / fs) + 1, np.floor(cen * nfft / fs) + 1, dtype=np.int)
lslope = heights[i] / (cen - low)
rid = np.arange(np.floor(cen * nfft / fs) + 1, np.floor(hi * nfft / fs) + 1, dtype=np.int)
rslope = heights[i] / (hi - cen)
fbank[i][lid] = lslope * (nfreqs[lid] - low)
fbank[i][rid] = rslope * (hi - nfreqs[rid])
return fbank, freqs
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