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124 lines
4.2 KiB
124 lines
4.2 KiB
/**
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* Copyright (c) 2022 Xiaomi Corporation (authors: Fangjun Kuang)
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*
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* See LICENSE for clarification regarding multiple authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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// This file is copied/modified from kaldi/src/feat/feature-fbank.cc
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//
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#include "frontend/feature-fbank.h"
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#include <cmath>
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#include "frontend/feature-functions.h"
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namespace knf {
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static void Sqrt(float *in_out, int32_t n) {
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for (int32_t i = 0; i != n; ++i) {
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in_out[i] = std::sqrt(in_out[i]);
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}
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}
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std::ostream &operator<<(std::ostream &os, const FbankOptions &opts) {
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os << opts.ToString();
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return os;
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}
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FbankComputer::FbankComputer(const FbankOptions &opts)
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: opts_(opts), rfft_(opts.frame_opts.PaddedWindowSize()) {
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if (opts.energy_floor > 0.0f) {
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log_energy_floor_ = logf(opts.energy_floor);
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}
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// We'll definitely need the filterbanks info for VTLN warping factor 1.0.
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// [note: this call caches it.]
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GetMelBanks(1.0f);
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}
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FbankComputer::~FbankComputer() {
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for (auto iter = mel_banks_.begin(); iter != mel_banks_.end(); ++iter)
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delete iter->second;
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}
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const MelBanks *FbankComputer::GetMelBanks(float vtln_warp) {
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MelBanks *this_mel_banks = nullptr;
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// std::map<float, MelBanks *>::iterator iter = mel_banks_.find(vtln_warp);
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auto iter = mel_banks_.find(vtln_warp);
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if (iter == mel_banks_.end()) {
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this_mel_banks =
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new MelBanks(opts_.mel_opts, opts_.frame_opts, vtln_warp);
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mel_banks_[vtln_warp] = this_mel_banks;
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} else {
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this_mel_banks = iter->second;
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}
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return this_mel_banks;
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}
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void FbankComputer::Compute(float signal_raw_log_energy,
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float vtln_warp,
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std::vector<float> *signal_frame,
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float *feature) {
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const MelBanks &mel_banks = *(GetMelBanks(vtln_warp));
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CHECK_EQ(signal_frame->size(), opts_.frame_opts.PaddedWindowSize());
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// Compute energy after window function (not the raw one).
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if (opts_.use_energy && !opts_.raw_energy) {
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signal_raw_log_energy =
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std::log(std::max<float>(InnerProduct(signal_frame->data(),
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signal_frame->data(),
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signal_frame->size()),
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std::numeric_limits<float>::epsilon()));
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}
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rfft_.Compute(signal_frame->data()); // signal_frame is modified in-place
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ComputePowerSpectrum(signal_frame);
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// Use magnitude instead of power if requested.
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if (!opts_.use_power) {
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Sqrt(signal_frame->data(), signal_frame->size() / 2 + 1);
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}
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int32_t mel_offset = ((opts_.use_energy && !opts_.htk_compat) ? 1 : 0);
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// Its length is opts_.mel_opts.num_bins
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float *mel_energies = feature + mel_offset;
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// Sum with mel filter banks over the power spectrum
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mel_banks.Compute(signal_frame->data(), mel_energies);
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if (opts_.use_log_fbank) {
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// Avoid log of zero (which should be prevented anyway by dithering).
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for (int32_t i = 0; i != opts_.mel_opts.num_bins; ++i) {
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auto t = std::max(mel_energies[i],
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std::numeric_limits<float>::epsilon());
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mel_energies[i] = std::log(t);
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}
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}
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// Copy energy as first value (or the last, if htk_compat == true).
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if (opts_.use_energy) {
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if (opts_.energy_floor > 0.0 &&
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signal_raw_log_energy < log_energy_floor_) {
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signal_raw_log_energy = log_energy_floor_;
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}
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int32_t energy_index = opts_.htk_compat ? opts_.mel_opts.num_bins : 0;
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feature[energy_index] = signal_raw_log_energy;
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}
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}
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} // namespace knf
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