feature-fbank.cc
4.56 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
// feat/feature-fbank.cc
// Copyright 2009-2012 Karel Vesely
// 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-fbank.h"
namespace kaldi {
FbankComputer::FbankComputer(const FbankOptions &opts):
opts_(opts), srfft_(NULL) {
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);
}
FbankComputer::FbankComputer(const FbankComputer &other):
opts_(other.opts_), log_energy_floor_(other.log_energy_floor_),
mel_banks_(other.mel_banks_), srfft_(NULL) {
for (std::map<BaseFloat, MelBanks*>::iterator iter = mel_banks_.begin();
iter != mel_banks_.end();
++iter)
iter->second = new MelBanks(*(iter->second));
if (other.srfft_)
srfft_ = new SplitRadixRealFft<BaseFloat>(*(other.srfft_));
}
FbankComputer::~FbankComputer() {
for (std::map<BaseFloat, MelBanks*>::iterator iter = mel_banks_.begin();
iter != mel_banks_.end(); ++iter)
delete iter->second;
delete srfft_;
}
const MelBanks* FbankComputer::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;
}
void FbankComputer::Compute(BaseFloat signal_raw_log_energy,
BaseFloat vtln_warp,
VectorBase<BaseFloat> *signal_frame,
VectorBase<BaseFloat> *feature) {
const MelBanks &mel_banks = *(GetMelBanks(vtln_warp));
KALDI_ASSERT(signal_frame->Dim() == opts_.frame_opts.PaddedWindowSize() &&
feature->Dim() == this->Dim());
// Compute energy after window function (not the raw one).
if (opts_.use_energy && !opts_.raw_energy)
signal_raw_log_energy = Log(std::max<BaseFloat>(VecVec(*signal_frame, *signal_frame),
std::numeric_limits<float>::min()));
if (srfft_ != NULL) // Compute FFT using 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);
// Use magnitude instead of power if requested.
if (!opts_.use_power)
power_spectrum.ApplyPow(0.5);
int32 mel_offset = ((opts_.use_energy && !opts_.htk_compat) ? 1 : 0);
SubVector<BaseFloat> mel_energies(*feature,
mel_offset,
opts_.mel_opts.num_bins);
// Sum with mel fiterbanks over the power spectrum
mel_banks.Compute(power_spectrum, &mel_energies);
if (opts_.use_log_fbank) {
// 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.
}
// Copy energy as first value (or the last, if htk_compat == true).
if (opts_.use_energy) {
if (opts_.energy_floor > 0.0 && signal_raw_log_energy < log_energy_floor_) {
signal_raw_log_energy = log_energy_floor_;
}
int32 energy_index = opts_.htk_compat ? opts_.mel_opts.num_bins : 0;
(*feature)(energy_index) = signal_raw_log_energy;
}
}
} // namespace kaldi