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/agc2/adaptive_digital_gain_applier.h"
12
13 #include <algorithm>
14
15 #include "common_audio/include/audio_util.h"
16 #include "modules/audio_processing/agc2/agc2_common.h"
17 #include "modules/audio_processing/logging/apm_data_dumper.h"
18 #include "rtc_base/checks.h"
19 #include "rtc_base/numerics/safe_minmax.h"
20 #include "system_wrappers/include/metrics.h"
21
22 namespace webrtc {
23 namespace {
24
25 // This function maps input level to desired applied gain. We want to
26 // boost the signal so that peaks are at -kHeadroomDbfs. We can't
27 // apply more than kMaxGainDb gain.
ComputeGainDb(float input_level_dbfs)28 float ComputeGainDb(float input_level_dbfs) {
29 // If the level is very low, boost it as much as we can.
30 if (input_level_dbfs < -(kHeadroomDbfs + kMaxGainDb)) {
31 return kMaxGainDb;
32 }
33
34 // We expect to end up here most of the time: the level is below
35 // -headroom, but we can boost it to -headroom.
36 if (input_level_dbfs < -kHeadroomDbfs) {
37 return -kHeadroomDbfs - input_level_dbfs;
38 }
39
40 // Otherwise, the level is too high and we can't boost. The
41 // LevelEstimator is responsible for not reporting bogus gain
42 // values.
43 RTC_DCHECK_LE(input_level_dbfs, 0.f);
44 return 0.f;
45 }
46
47 // We require 'gain + noise_level <= kMaxNoiseLevelDbfs'.
LimitGainByNoise(float target_gain,float input_noise_level_dbfs,ApmDataDumper * apm_data_dumper)48 float LimitGainByNoise(float target_gain,
49 float input_noise_level_dbfs,
50 ApmDataDumper* apm_data_dumper) {
51 const float noise_headroom_db = kMaxNoiseLevelDbfs - input_noise_level_dbfs;
52 apm_data_dumper->DumpRaw("agc2_noise_headroom_db", noise_headroom_db);
53 return std::min(target_gain, std::max(noise_headroom_db, 0.f));
54 }
55
LimitGainByLowConfidence(float target_gain,float last_gain,float limiter_audio_level_dbfs,bool estimate_is_confident)56 float LimitGainByLowConfidence(float target_gain,
57 float last_gain,
58 float limiter_audio_level_dbfs,
59 bool estimate_is_confident) {
60 if (estimate_is_confident ||
61 limiter_audio_level_dbfs <= kLimiterThresholdForAgcGainDbfs) {
62 return target_gain;
63 }
64 const float limiter_level_before_gain = limiter_audio_level_dbfs - last_gain;
65
66 // Compute a new gain so that limiter_level_before_gain + new_gain <=
67 // kLimiterThreshold.
68 const float new_target_gain = std::max(
69 kLimiterThresholdForAgcGainDbfs - limiter_level_before_gain, 0.f);
70 return std::min(new_target_gain, target_gain);
71 }
72
73 // Computes how the gain should change during this frame.
74 // Return the gain difference in db to 'last_gain_db'.
ComputeGainChangeThisFrameDb(float target_gain_db,float last_gain_db,bool gain_increase_allowed)75 float ComputeGainChangeThisFrameDb(float target_gain_db,
76 float last_gain_db,
77 bool gain_increase_allowed) {
78 float target_gain_difference_db = target_gain_db - last_gain_db;
79 if (!gain_increase_allowed) {
80 target_gain_difference_db = std::min(target_gain_difference_db, 0.f);
81 }
82
83 return rtc::SafeClamp(target_gain_difference_db, -kMaxGainChangePerFrameDb,
84 kMaxGainChangePerFrameDb);
85 }
86 } // namespace
87
SignalWithLevels(AudioFrameView<float> float_frame)88 SignalWithLevels::SignalWithLevels(AudioFrameView<float> float_frame)
89 : float_frame(float_frame) {}
90 SignalWithLevels::SignalWithLevels(const SignalWithLevels&) = default;
91
AdaptiveDigitalGainApplier(ApmDataDumper * apm_data_dumper)92 AdaptiveDigitalGainApplier::AdaptiveDigitalGainApplier(
93 ApmDataDumper* apm_data_dumper)
94 : gain_applier_(false, DbToRatio(last_gain_db_)),
95 apm_data_dumper_(apm_data_dumper) {}
96
Process(SignalWithLevels signal_with_levels)97 void AdaptiveDigitalGainApplier::Process(SignalWithLevels signal_with_levels) {
98 calls_since_last_gain_log_++;
99 if (calls_since_last_gain_log_ == 100) {
100 calls_since_last_gain_log_ = 0;
101 RTC_HISTOGRAM_COUNTS_LINEAR("WebRTC.Audio.Agc2.DigitalGainApplied",
102 last_gain_db_, 0, kMaxGainDb, kMaxGainDb + 1);
103 RTC_HISTOGRAM_COUNTS_LINEAR("WebRTC.Audio.Agc2.EstimatedNoiseLevel",
104 -signal_with_levels.input_noise_level_dbfs, 0,
105 100, 101);
106 }
107
108 signal_with_levels.input_level_dbfs =
109 std::min(signal_with_levels.input_level_dbfs, 0.f);
110
111 RTC_DCHECK_GE(signal_with_levels.input_level_dbfs, -150.f);
112 RTC_DCHECK_GE(signal_with_levels.float_frame.num_channels(), 1);
113 RTC_DCHECK_GE(signal_with_levels.float_frame.samples_per_channel(), 1);
114
115 const float target_gain_db = LimitGainByLowConfidence(
116 LimitGainByNoise(ComputeGainDb(signal_with_levels.input_level_dbfs),
117 signal_with_levels.input_noise_level_dbfs,
118 apm_data_dumper_),
119 last_gain_db_, signal_with_levels.limiter_audio_level_dbfs,
120 signal_with_levels.estimate_is_confident);
121
122 // Forbid increasing the gain when there is no speech.
123 gain_increase_allowed_ = signal_with_levels.vad_result.speech_probability >
124 kVadConfidenceThreshold;
125
126 const float gain_change_this_frame_db = ComputeGainChangeThisFrameDb(
127 target_gain_db, last_gain_db_, gain_increase_allowed_);
128
129 apm_data_dumper_->DumpRaw("agc2_want_to_change_by_db",
130 target_gain_db - last_gain_db_);
131 apm_data_dumper_->DumpRaw("agc2_will_change_by_db",
132 gain_change_this_frame_db);
133
134 // Optimization: avoid calling math functions if gain does not
135 // change.
136 if (gain_change_this_frame_db != 0.f) {
137 gain_applier_.SetGainFactor(
138 DbToRatio(last_gain_db_ + gain_change_this_frame_db));
139 }
140 gain_applier_.ApplyGain(signal_with_levels.float_frame);
141
142 // Remember that the gain has changed for the next iteration.
143 last_gain_db_ = last_gain_db_ + gain_change_this_frame_db;
144 apm_data_dumper_->DumpRaw("agc2_applied_gain_db", last_gain_db_);
145 }
146 } // namespace webrtc
147