1 /*
2 * Copyright (c) 2018 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/reverb_frequency_response.h"
12
13 #include <stddef.h>
14
15 #include <algorithm>
16 #include <array>
17 #include <numeric>
18
19 #include "api/array_view.h"
20 #include "modules/audio_processing/aec3/aec3_common.h"
21 #include "rtc_base/checks.h"
22
23 namespace webrtc {
24
25 namespace {
26
27 // Computes the ratio of the energies between the direct path and the tail. The
28 // energy is computed in the power spectrum domain discarding the DC
29 // contributions.
AverageDecayWithinFilter(rtc::ArrayView<const float> freq_resp_direct_path,rtc::ArrayView<const float> freq_resp_tail)30 float AverageDecayWithinFilter(
31 rtc::ArrayView<const float> freq_resp_direct_path,
32 rtc::ArrayView<const float> freq_resp_tail) {
33 // Skipping the DC for the ratio computation
34 constexpr size_t kSkipBins = 1;
35 RTC_CHECK_EQ(freq_resp_direct_path.size(), freq_resp_tail.size());
36
37 float direct_path_energy =
38 std::accumulate(freq_resp_direct_path.begin() + kSkipBins,
39 freq_resp_direct_path.end(), 0.f);
40
41 if (direct_path_energy == 0.f) {
42 return 0.f;
43 }
44
45 float tail_energy = std::accumulate(freq_resp_tail.begin() + kSkipBins,
46 freq_resp_tail.end(), 0.f);
47 return tail_energy / direct_path_energy;
48 }
49
50 } // namespace
51
ReverbFrequencyResponse()52 ReverbFrequencyResponse::ReverbFrequencyResponse() {
53 tail_response_.fill(0.f);
54 }
55 ReverbFrequencyResponse::~ReverbFrequencyResponse() = default;
56
Update(const std::vector<std::array<float,kFftLengthBy2Plus1>> & frequency_response,int filter_delay_blocks,const absl::optional<float> & linear_filter_quality,bool stationary_block)57 void ReverbFrequencyResponse::Update(
58 const std::vector<std::array<float, kFftLengthBy2Plus1>>&
59 frequency_response,
60 int filter_delay_blocks,
61 const absl::optional<float>& linear_filter_quality,
62 bool stationary_block) {
63 if (stationary_block || !linear_filter_quality) {
64 return;
65 }
66
67 Update(frequency_response, filter_delay_blocks, *linear_filter_quality);
68 }
69
Update(const std::vector<std::array<float,kFftLengthBy2Plus1>> & frequency_response,int filter_delay_blocks,float linear_filter_quality)70 void ReverbFrequencyResponse::Update(
71 const std::vector<std::array<float, kFftLengthBy2Plus1>>&
72 frequency_response,
73 int filter_delay_blocks,
74 float linear_filter_quality) {
75 rtc::ArrayView<const float> freq_resp_tail(
76 frequency_response[frequency_response.size() - 1]);
77
78 rtc::ArrayView<const float> freq_resp_direct_path(
79 frequency_response[filter_delay_blocks]);
80
81 float average_decay =
82 AverageDecayWithinFilter(freq_resp_direct_path, freq_resp_tail);
83
84 const float smoothing = 0.2f * linear_filter_quality;
85 average_decay_ += smoothing * (average_decay - average_decay_);
86
87 for (size_t k = 0; k < kFftLengthBy2Plus1; ++k) {
88 tail_response_[k] = freq_resp_direct_path[k] * average_decay_;
89 }
90
91 for (size_t k = 1; k < kFftLengthBy2; ++k) {
92 const float avg_neighbour =
93 0.5f * (tail_response_[k - 1] + tail_response_[k + 1]);
94 tail_response_[k] = std::max(tail_response_[k], avg_neighbour);
95 }
96 }
97
98 } // namespace webrtc
99