1 /*
2 * Copyright (c) 2019 The WebRTC project authors. All Rights Reserved.
3 *
4 * Use of this source code is governed by a BSD-style license
5 * that can be found in the LICENSE file in the root of the source
6 * tree. An additional intellectual property rights grant can be found
7 * in the file PATENTS. All contributing project authors may
8 * be found in the AUTHORS file in the root of the source tree.
9 */
10
11 #include "modules/audio_processing/ns/speech_probability_estimator.h"
12
13 #include <math.h>
14 #include <algorithm>
15
16 #include "modules/audio_processing/ns/fast_math.h"
17 #include "rtc_base/checks.h"
18
19 namespace webrtc {
20
SpeechProbabilityEstimator()21 SpeechProbabilityEstimator::SpeechProbabilityEstimator() {
22 speech_probability_.fill(0.f);
23 }
24
Update(int32_t num_analyzed_frames,rtc::ArrayView<const float,kFftSizeBy2Plus1> prior_snr,rtc::ArrayView<const float,kFftSizeBy2Plus1> post_snr,rtc::ArrayView<const float,kFftSizeBy2Plus1> conservative_noise_spectrum,rtc::ArrayView<const float,kFftSizeBy2Plus1> signal_spectrum,float signal_spectral_sum,float signal_energy)25 void SpeechProbabilityEstimator::Update(
26 int32_t num_analyzed_frames,
27 rtc::ArrayView<const float, kFftSizeBy2Plus1> prior_snr,
28 rtc::ArrayView<const float, kFftSizeBy2Plus1> post_snr,
29 rtc::ArrayView<const float, kFftSizeBy2Plus1> conservative_noise_spectrum,
30 rtc::ArrayView<const float, kFftSizeBy2Plus1> signal_spectrum,
31 float signal_spectral_sum,
32 float signal_energy) {
33 // Update models.
34 if (num_analyzed_frames < kLongStartupPhaseBlocks) {
35 signal_model_estimator_.AdjustNormalization(num_analyzed_frames,
36 signal_energy);
37 }
38 signal_model_estimator_.Update(prior_snr, post_snr,
39 conservative_noise_spectrum, signal_spectrum,
40 signal_spectral_sum, signal_energy);
41
42 const SignalModel& model = signal_model_estimator_.get_model();
43 const PriorSignalModel& prior_model =
44 signal_model_estimator_.get_prior_model();
45
46 // Width parameter in sigmoid map for prior model.
47 constexpr float kWidthPrior0 = 4.f;
48 // Width for pause region: lower range, so increase width in tanh map.
49 constexpr float kWidthPrior1 = 2.f * kWidthPrior0;
50
51 // Average LRT feature: use larger width in tanh map for pause regions.
52 float width_prior = model.lrt < prior_model.lrt ? kWidthPrior1 : kWidthPrior0;
53
54 // Compute indicator function: sigmoid map.
55 float indicator0 =
56 0.5f * (tanh(width_prior * (model.lrt - prior_model.lrt)) + 1.f);
57
58 // Spectral flatness feature: use larger width in tanh map for pause regions.
59 width_prior = model.spectral_flatness > prior_model.flatness_threshold
60 ? kWidthPrior1
61 : kWidthPrior0;
62
63 // Compute indicator function: sigmoid map.
64 float indicator1 =
65 0.5f * (tanh(1.f * width_prior *
66 (prior_model.flatness_threshold - model.spectral_flatness)) +
67 1.f);
68
69 // For template spectrum-difference : use larger width in tanh map for pause
70 // regions.
71 width_prior = model.spectral_diff < prior_model.template_diff_threshold
72 ? kWidthPrior1
73 : kWidthPrior0;
74
75 // Compute indicator function: sigmoid map.
76 float indicator2 =
77 0.5f * (tanh(width_prior * (model.spectral_diff -
78 prior_model.template_diff_threshold)) +
79 1.f);
80
81 // Combine the indicator function with the feature weights.
82 float ind_prior = prior_model.lrt_weighting * indicator0 +
83 prior_model.flatness_weighting * indicator1 +
84 prior_model.difference_weighting * indicator2;
85
86 // Compute the prior probability.
87 prior_speech_prob_ += 0.1f * (ind_prior - prior_speech_prob_);
88
89 // Make sure probabilities are within range: keep floor to 0.01.
90 prior_speech_prob_ = std::max(std::min(prior_speech_prob_, 1.f), 0.01f);
91
92 // Final speech probability: combine prior model with LR factor:.
93 float gain_prior =
94 (1.f - prior_speech_prob_) / (prior_speech_prob_ + 0.0001f);
95
96 std::array<float, kFftSizeBy2Plus1> inv_lrt;
97 ExpApproximationSignFlip(model.avg_log_lrt, inv_lrt);
98 for (size_t i = 0; i < kFftSizeBy2Plus1; ++i) {
99 speech_probability_[i] = 1.f / (1.f + gain_prior * inv_lrt[i]);
100 }
101 }
102
103 } // namespace webrtc
104