feature-mfcc.cc
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// feat/feature-mfcc.cc
// Copyright 2009-2011 Karel Vesely; Petr Motlicek
// 2016 Johns Hopkins University (author: Daniel Povey)
// See ../../COPYING for clarification regarding multiple authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// THIS CODE IS PROVIDED *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED
// WARRANTIES OR CONDITIONS OF TITLE, FITNESS FOR A PARTICULAR PURPOSE,
// MERCHANTABLITY OR NON-INFRINGEMENT.
// See the Apache 2 License for the specific language governing permissions and
// limitations under the License.
#include "feat/feature-mfcc.h"
namespace kaldi {
void MfccComputer::Compute(BaseFloat signal_raw_log_energy,
BaseFloat vtln_warp,
VectorBase<BaseFloat> *signal_frame,
VectorBase<BaseFloat> *feature) {
KALDI_ASSERT(signal_frame->Dim() == opts_.frame_opts.PaddedWindowSize() &&
feature->Dim() == this->Dim());
const MelBanks &mel_banks = *(GetMelBanks(vtln_warp));
if (opts_.use_energy && !opts_.raw_energy)
signal_raw_log_energy = Log(std::max<BaseFloat>(VecVec(*signal_frame, *signal_frame),
std::numeric_limits<float>::epsilon()));
if (srfft_ != NULL) // Compute FFT using the split-radix algorithm.
srfft_->Compute(signal_frame->Data(), true);
else // An alternative algorithm that works for non-powers-of-two.
RealFft(signal_frame, true);
// Convert the FFT into a power spectrum.
ComputePowerSpectrum(signal_frame);
SubVector<BaseFloat> power_spectrum(*signal_frame, 0,
signal_frame->Dim() / 2 + 1);
mel_banks.Compute(power_spectrum, &mel_energies_);
// avoid log of zero (which should be prevented anyway by dithering).
mel_energies_.ApplyFloor(std::numeric_limits<float>::epsilon());
mel_energies_.ApplyLog(); // take the log.
feature->SetZero(); // in case there were NaNs.
// feature = dct_matrix_ * mel_energies [which now have log]
feature->AddMatVec(1.0, dct_matrix_, kNoTrans, mel_energies_, 0.0);
if (opts_.cepstral_lifter != 0.0)
feature->MulElements(lifter_coeffs_);
if (opts_.use_energy) {
if (opts_.energy_floor > 0.0 && signal_raw_log_energy < log_energy_floor_)
signal_raw_log_energy = log_energy_floor_;
(*feature)(0) = signal_raw_log_energy;
}
if (opts_.htk_compat) {
BaseFloat energy = (*feature)(0);
for (int32 i = 0; i < opts_.num_ceps - 1; i++)
(*feature)(i) = (*feature)(i+1);
if (!opts_.use_energy)
energy *= M_SQRT2; // scale on C0 (actually removing a scale
// we previously added that's part of one common definition of
// the cosine transform.)
(*feature)(opts_.num_ceps - 1) = energy;
}
}
MfccComputer::MfccComputer(const MfccOptions &opts):
opts_(opts), srfft_(NULL),
mel_energies_(opts.mel_opts.num_bins) {
int32 num_bins = opts.mel_opts.num_bins;
if (opts.num_ceps > num_bins)
KALDI_ERR << "num-ceps cannot be larger than num-mel-bins."
<< " It should be smaller or equal. You provided num-ceps: "
<< opts.num_ceps << " and num-mel-bins: "
<< num_bins;
Matrix<BaseFloat> dct_matrix(num_bins, num_bins);
ComputeDctMatrix(&dct_matrix);
// Note that we include zeroth dct in either case. If using the
// energy we replace this with the energy. This means a different
// ordering of features than HTK.
SubMatrix<BaseFloat> dct_rows(dct_matrix, 0, opts.num_ceps, 0, num_bins);
dct_matrix_.Resize(opts.num_ceps, num_bins);
dct_matrix_.CopyFromMat(dct_rows); // subset of rows.
if (opts.cepstral_lifter != 0.0) {
lifter_coeffs_.Resize(opts.num_ceps);
ComputeLifterCoeffs(opts.cepstral_lifter, &lifter_coeffs_);
}
if (opts.energy_floor > 0.0)
log_energy_floor_ = Log(opts.energy_floor);
int32 padded_window_size = opts.frame_opts.PaddedWindowSize();
if ((padded_window_size & (padded_window_size-1)) == 0) // Is a power of two...
srfft_ = new SplitRadixRealFft<BaseFloat>(padded_window_size);
// We'll definitely need the filterbanks info for VTLN warping factor 1.0.
// [note: this call caches it.]
GetMelBanks(1.0);
}
MfccComputer::MfccComputer(const MfccComputer &other):
opts_(other.opts_), lifter_coeffs_(other.lifter_coeffs_),
dct_matrix_(other.dct_matrix_),
log_energy_floor_(other.log_energy_floor_),
mel_banks_(other.mel_banks_),
srfft_(NULL),
mel_energies_(other.mel_energies_.Dim(), kUndefined) {
for (std::map<BaseFloat, MelBanks*>::iterator iter = mel_banks_.begin();
iter != mel_banks_.end(); ++iter)
iter->second = new MelBanks(*(iter->second));
if (other.srfft_ != NULL)
srfft_ = new SplitRadixRealFft<BaseFloat>(*(other.srfft_));
}
MfccComputer::~MfccComputer() {
for (std::map<BaseFloat, MelBanks*>::iterator iter = mel_banks_.begin();
iter != mel_banks_.end();
++iter)
delete iter->second;
delete srfft_;
}
const MelBanks *MfccComputer::GetMelBanks(BaseFloat vtln_warp) {
MelBanks *this_mel_banks = NULL;
std::map<BaseFloat, MelBanks*>::iterator iter = mel_banks_.find(vtln_warp);
if (iter == mel_banks_.end()) {
this_mel_banks = new MelBanks(opts_.mel_opts,
opts_.frame_opts,
vtln_warp);
mel_banks_[vtln_warp] = this_mel_banks;
} else {
this_mel_banks = iter->second;
}
return this_mel_banks;
}
} // namespace kaldi