1 /*
2 * Copyright (c) 2017 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/aec3/render_signal_analyzer.h"
12
13 #include <math.h>
14 #include <algorithm>
15
16 #include "rtc_base/checks.h"
17
18 namespace webrtc {
19
20 namespace {
21 constexpr size_t kCounterThreshold = 5;
22
23 // Identifies local bands with narrow characteristics.
IdentifySmallNarrowBandRegions(const RenderBuffer & render_buffer,const rtc::Optional<size_t> & delay_partitions,std::array<size_t,kFftLengthBy2-1> * narrow_band_counters)24 void IdentifySmallNarrowBandRegions(
25 const RenderBuffer& render_buffer,
26 const rtc::Optional<size_t>& delay_partitions,
27 std::array<size_t, kFftLengthBy2 - 1>* narrow_band_counters) {
28 if (!delay_partitions) {
29 narrow_band_counters->fill(0);
30 return;
31 }
32
33 const std::array<float, kFftLengthBy2Plus1>& X2 =
34 render_buffer.Spectrum(*delay_partitions);
35
36 for (size_t k = 1; k < (X2.size() - 1); ++k) {
37 (*narrow_band_counters)[k - 1] = X2[k] > 3 * std::max(X2[k - 1], X2[k + 1])
38 ? (*narrow_band_counters)[k - 1] + 1
39 : 0;
40 }
41 }
42
43 // Identifies whether the signal has a single strong narrow-band component.
IdentifyStrongNarrowBandComponent(const RenderBuffer & render_buffer,rtc::Optional<int> * narrow_peak_band,size_t * narrow_peak_counter)44 void IdentifyStrongNarrowBandComponent(const RenderBuffer& render_buffer,
45 rtc::Optional<int>* narrow_peak_band,
46 size_t* narrow_peak_counter) {
47 const auto X2_latest = render_buffer.Spectrum(0);
48
49 // Identify the spectral peak.
50 const int peak_bin = static_cast<int>(
51 std::max_element(X2_latest.begin(), X2_latest.end()) - X2_latest.begin());
52
53 // Compute the level around the peak.
54 float non_peak_power = 0.f;
55 for (int k = std::max(5, peak_bin - 14); k < peak_bin - 4; ++k) {
56 non_peak_power = std::max(X2_latest[k], non_peak_power);
57 }
58 for (int k = peak_bin + 5;
59 k < std::min(peak_bin + 15, static_cast<int>(kFftLengthBy2Plus1)); ++k) {
60 non_peak_power = std::max(X2_latest[k], non_peak_power);
61 }
62
63 // Assess the render signal strength
64 const std::vector<std::vector<float>>& x_latest =
65 render_buffer.MostRecentBlock();
66 auto result0 = std::minmax_element(x_latest[0].begin(), x_latest[0].end());
67 float max_abs = std::max(fabs(*result0.first), fabs(*result0.second));
68
69 if (x_latest.size() > 1) {
70 const auto result1 =
71 std::minmax_element(x_latest[1].begin(), x_latest[1].end());
72 max_abs =
73 std::max(max_abs, static_cast<float>(std::max(fabs(*result1.first),
74 fabs(*result1.second))));
75 }
76
77 // Detect whether the spectal peak has as strong narrowband nature.
78 if (peak_bin > 6 && max_abs > 100 &&
79 X2_latest[peak_bin] > 100 * non_peak_power) {
80 *narrow_peak_band = peak_bin;
81 *narrow_peak_counter = 0;
82 } else {
83 if (*narrow_peak_band && ++(*narrow_peak_counter) > 7) {
84 *narrow_peak_band = rtc::nullopt;
85 }
86 }
87 }
88
89 } // namespace
90
RenderSignalAnalyzer()91 RenderSignalAnalyzer::RenderSignalAnalyzer() {
92 narrow_band_counters_.fill(0);
93 }
94 RenderSignalAnalyzer::~RenderSignalAnalyzer() = default;
95
Update(const RenderBuffer & render_buffer,const rtc::Optional<size_t> & delay_partitions)96 void RenderSignalAnalyzer::Update(
97 const RenderBuffer& render_buffer,
98 const rtc::Optional<size_t>& delay_partitions) {
99 // Identify bands of narrow nature.
100 IdentifySmallNarrowBandRegions(render_buffer, delay_partitions,
101 &narrow_band_counters_);
102
103 // Identify the presence of a strong narrow band.
104 IdentifyStrongNarrowBandComponent(render_buffer, &narrow_peak_band_,
105 &narrow_peak_counter_);
106 }
107
MaskRegionsAroundNarrowBands(std::array<float,kFftLengthBy2Plus1> * v) const108 void RenderSignalAnalyzer::MaskRegionsAroundNarrowBands(
109 std::array<float, kFftLengthBy2Plus1>* v) const {
110 RTC_DCHECK(v);
111
112 // Set v to zero around narrow band signal regions.
113 if (narrow_band_counters_[0] > kCounterThreshold) {
114 (*v)[1] = (*v)[0] = 0.f;
115 }
116 for (size_t k = 2; k < kFftLengthBy2 - 1; ++k) {
117 if (narrow_band_counters_[k - 1] > kCounterThreshold) {
118 (*v)[k - 2] = (*v)[k - 1] = (*v)[k] = (*v)[k + 1] = (*v)[k + 2] = 0.f;
119 }
120 }
121 if (narrow_band_counters_[kFftLengthBy2 - 2] > kCounterThreshold) {
122 (*v)[kFftLengthBy2] = (*v)[kFftLengthBy2 - 1] = 0.f;
123 }
124 }
125
126 } // namespace webrtc
127