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/*
* Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include "modules/audio_processing/aec3/suppression_gain.h"
#include <math.h>
#include <stddef.h>
#include <algorithm>
#include <numeric>
#include "modules/audio_processing/aec3/dominant_nearend_detector.h"
#include "modules/audio_processing/aec3/moving_average.h"
#include "modules/audio_processing/aec3/subband_nearend_detector.h"
#include "modules/audio_processing/aec3/vector_math.h"
#include "modules/audio_processing/logging/apm_data_dumper.h"
#include "rtc_base/checks.h"
#include "system_wrappers/include/field_trial.h"
namespace webrtc {
namespace {
void LimitLowFrequencyGains(std::array<float, kFftLengthBy2Plus1>* gain) {
// Limit the low frequency gains to avoid the impact of the high-pass filter
// on the lower-frequency gain influencing the overall achieved gain.
(*gain)[0] = (*gain)[1] = std::min((*gain)[1], (*gain)[2]);
}
void LimitHighFrequencyGains(bool conservative_hf_suppression,
std::array<float, kFftLengthBy2Plus1>* gain) {
// Limit the high frequency gains to avoid echo leakage due to an imperfect
// filter.
constexpr size_t kFirstBandToLimit = (64 * 2000) / 8000;
const float min_upper_gain = (*gain)[kFirstBandToLimit];
std::for_each(
gain->begin() + kFirstBandToLimit + 1, gain->end(),
[min_upper_gain](float& a) { a = std::min(a, min_upper_gain); });
(*gain)[kFftLengthBy2] = (*gain)[kFftLengthBy2Minus1];
if (conservative_hf_suppression) {
// Limits the gain in the frequencies for which the adaptive filter has not
// converged.
// TODO(peah): Make adaptive to take the actual filter error into account.
constexpr size_t kUpperAccurateBandPlus1 = 29;
constexpr float oneByBandsInSum =
1 / static_cast<float>(kUpperAccurateBandPlus1 - 20);
const float hf_gain_bound =
std::accumulate(gain->begin() + 20,
gain->begin() + kUpperAccurateBandPlus1, 0.f) *
oneByBandsInSum;
std::for_each(
gain->begin() + kUpperAccurateBandPlus1, gain->end(),
[hf_gain_bound](float& a) { a = std::min(a, hf_gain_bound); });
}
}
// Scales the echo according to assessed audibility at the other end.
void WeightEchoForAudibility(const EchoCanceller3Config& config,
rtc::ArrayView<const float> echo,
rtc::ArrayView<float> weighted_echo) {
RTC_DCHECK_EQ(kFftLengthBy2Plus1, echo.size());
RTC_DCHECK_EQ(kFftLengthBy2Plus1, weighted_echo.size());
auto weigh = [](float threshold, float normalizer, size_t begin, size_t end,
rtc::ArrayView<const float> echo,
rtc::ArrayView<float> weighted_echo) {
for (size_t k = begin; k < end; ++k) {
if (echo[k] < threshold) {
float tmp = (threshold - echo[k]) * normalizer;
weighted_echo[k] = echo[k] * std::max(0.f, 1.f - tmp * tmp);
} else {
weighted_echo[k] = echo[k];
}
}
};
float threshold = config.echo_audibility.floor_power *
config.echo_audibility.audibility_threshold_lf;
float normalizer = 1.f / (threshold - config.echo_audibility.floor_power);
weigh(threshold, normalizer, 0, 3, echo, weighted_echo);
threshold = config.echo_audibility.floor_power *
config.echo_audibility.audibility_threshold_mf;
normalizer = 1.f / (threshold - config.echo_audibility.floor_power);
weigh(threshold, normalizer, 3, 7, echo, weighted_echo);
threshold = config.echo_audibility.floor_power *
config.echo_audibility.audibility_threshold_hf;
normalizer = 1.f / (threshold - config.echo_audibility.floor_power);
weigh(threshold, normalizer, 7, kFftLengthBy2Plus1, echo, weighted_echo);
}
} // namespace
std::atomic<int> SuppressionGain::instance_count_(0);
float SuppressionGain::UpperBandsGain(
rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>> echo_spectrum,
rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>>
comfort_noise_spectrum,
const std::optional<int>& narrow_peak_band,
bool saturated_echo,
const Block& render,
const std::array<float, kFftLengthBy2Plus1>& low_band_gain) const {
RTC_DCHECK_LT(0, render.NumBands());
if (render.NumBands() == 1) {
return 1.f;
}
const int num_render_channels = render.NumChannels();
if (narrow_peak_band &&
(*narrow_peak_band > static_cast<int>(kFftLengthBy2Plus1 - 10))) {
return 0.001f;
}
constexpr size_t kLowBandGainLimit = kFftLengthBy2 / 2;
const float gain_below_8_khz = *std::min_element(
low_band_gain.begin() + kLowBandGainLimit, low_band_gain.end());
// Always attenuate the upper bands when there is saturated echo.
if (saturated_echo) {
return std::min(0.001f, gain_below_8_khz);
}
// Compute the upper and lower band energies.
const auto sum_of_squares = [](float a, float b) { return a + b * b; };
float low_band_energy = 0.f;
for (int ch = 0; ch < num_render_channels; ++ch) {
const float channel_energy =
std::accumulate(render.begin(/*band=*/0, ch),
render.end(/*band=*/0, ch), 0.0f, sum_of_squares);
low_band_energy = std::max(low_band_energy, channel_energy);
}
float high_band_energy = 0.f;
for (int k = 1; k < render.NumBands(); ++k) {
for (int ch = 0; ch < num_render_channels; ++ch) {
const float energy = std::accumulate(
render.begin(k, ch), render.end(k, ch), 0.f, sum_of_squares);
high_band_energy = std::max(high_band_energy, energy);
}
}
// If there is more power in the lower frequencies than the upper frequencies,
// or if the power in upper frequencies is low, do not bound the gain in the
// upper bands.
float anti_howling_gain;
const float activation_threshold =
kBlockSize * config_.suppressor.high_bands_suppression
.anti_howling_activation_threshold;
if (high_band_energy < std::max(low_band_energy, activation_threshold)) {
anti_howling_gain = 1.f;
} else {
// In all other cases, bound the gain for upper frequencies.
RTC_DCHECK_LE(low_band_energy, high_band_energy);
RTC_DCHECK_NE(0.f, high_band_energy);
anti_howling_gain =
config_.suppressor.high_bands_suppression.anti_howling_gain *
sqrtf(low_band_energy / high_band_energy);
}
float gain_bound = 1.f;
if (!dominant_nearend_detector_->IsNearendState()) {
// Bound the upper gain during significant echo activity.
const auto& cfg = config_.suppressor.high_bands_suppression;
auto low_frequency_energy = [](rtc::ArrayView<const float> spectrum) {
RTC_DCHECK_LE(16, spectrum.size());
return std::accumulate(spectrum.begin() + 1, spectrum.begin() + 16, 0.f);
};
for (size_t ch = 0; ch < num_capture_channels_; ++ch) {
const float echo_sum = low_frequency_energy(echo_spectrum[ch]);
const float noise_sum = low_frequency_energy(comfort_noise_spectrum[ch]);
if (echo_sum > cfg.enr_threshold * noise_sum) {
gain_bound = cfg.max_gain_during_echo;
break;
}
}
}
// Choose the gain as the minimum of the lower and upper gains.
return std::min(std::min(gain_below_8_khz, anti_howling_gain), gain_bound);
}
// Computes the gain to reduce the echo to a non audible level.
void SuppressionGain::GainToNoAudibleEcho(
const std::array<float, kFftLengthBy2Plus1>& nearend,
const std::array<float, kFftLengthBy2Plus1>& echo,
const std::array<float, kFftLengthBy2Plus1>& masker,
std::array<float, kFftLengthBy2Plus1>* gain) const {
const auto& p = dominant_nearend_detector_->IsNearendState() ? nearend_params_
: normal_params_;
for (size_t k = 0; k < gain->size(); ++k) {
float enr = echo[k] / (nearend[k] + 1.f); // Echo-to-nearend ratio.
float emr = echo[k] / (masker[k] + 1.f); // Echo-to-masker (noise) ratio.
float g = 1.0f;
if (enr > p.enr_transparent_[k] && emr > p.emr_transparent_[k]) {
g = (p.enr_suppress_[k] - enr) /
(p.enr_suppress_[k] - p.enr_transparent_[k]);
g = std::max(g, p.emr_transparent_[k] / emr);
}
(*gain)[k] = g;
}
}
// Compute the minimum gain as the attenuating gain to put the signal just
// above the zero sample values.
void SuppressionGain::GetMinGain(
rtc::ArrayView<const float> weighted_residual_echo,
rtc::ArrayView<const float> last_nearend,
rtc::ArrayView<const float> last_echo,
bool low_noise_render,
bool saturated_echo,
rtc::ArrayView<float> min_gain) const {
if (!saturated_echo) {
const float min_echo_power =
low_noise_render ? config_.echo_audibility.low_render_limit
: config_.echo_audibility.normal_render_limit;
for (size_t k = 0; k < min_gain.size(); ++k) {
min_gain[k] = weighted_residual_echo[k] > 0.f
? min_echo_power / weighted_residual_echo[k]
: 1.f;
min_gain[k] = std::min(min_gain[k], 1.f);
}
if (!initial_state_ ||
config_.suppressor.lf_smoothing_during_initial_phase) {
const float& dec = dominant_nearend_detector_->IsNearendState()
? nearend_params_.max_dec_factor_lf
: normal_params_.max_dec_factor_lf;
for (int k = 0; k <= config_.suppressor.last_lf_smoothing_band; ++k) {
// Make sure the gains of the low frequencies do not decrease too
// quickly after strong nearend.
if (last_nearend[k] > last_echo[k] ||
k <= config_.suppressor.last_permanent_lf_smoothing_band) {
min_gain[k] = std::max(min_gain[k], last_gain_[k] * dec);
min_gain[k] = std::min(min_gain[k], 1.f);
}
}
}
} else {
std::fill(min_gain.begin(), min_gain.end(), 0.f);
}
}
// Compute the maximum gain by limiting the gain increase from the previous
// gain.
void SuppressionGain::GetMaxGain(rtc::ArrayView<float> max_gain) const {
const auto& inc = dominant_nearend_detector_->IsNearendState()
? nearend_params_.max_inc_factor
: normal_params_.max_inc_factor;
const auto& floor = config_.suppressor.floor_first_increase;
for (size_t k = 0; k < max_gain.size(); ++k) {
max_gain[k] = std::min(std::max(last_gain_[k] * inc, floor), 1.f);
}
}
void SuppressionGain::LowerBandGain(
bool low_noise_render,
const AecState& aec_state,
rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>>
suppressor_input,
rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>> residual_echo,
rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>> comfort_noise,
bool clock_drift,
std::array<float, kFftLengthBy2Plus1>* gain) {
gain->fill(1.f);
const bool saturated_echo = aec_state.SaturatedEcho();
std::array<float, kFftLengthBy2Plus1> max_gain;
GetMaxGain(max_gain);
for (size_t ch = 0; ch < num_capture_channels_; ++ch) {
std::array<float, kFftLengthBy2Plus1> G;
std::array<float, kFftLengthBy2Plus1> nearend;
nearend_smoothers_[ch].Average(suppressor_input[ch], nearend);
// Weight echo power in terms of audibility.
std::array<float, kFftLengthBy2Plus1> weighted_residual_echo;
WeightEchoForAudibility(config_, residual_echo[ch], weighted_residual_echo);
std::array<float, kFftLengthBy2Plus1> min_gain;
GetMinGain(weighted_residual_echo, last_nearend_[ch], last_echo_[ch],
low_noise_render, saturated_echo, min_gain);
GainToNoAudibleEcho(nearend, weighted_residual_echo, comfort_noise[0], &G);
// Clamp gains.
for (size_t k = 0; k < gain->size(); ++k) {
G[k] = std::max(std::min(G[k], max_gain[k]), min_gain[k]);
(*gain)[k] = std::min((*gain)[k], G[k]);
}
// Store data required for the gain computation of the next block.
std::copy(nearend.begin(), nearend.end(), last_nearend_[ch].begin());
std::copy(weighted_residual_echo.begin(), weighted_residual_echo.end(),
last_echo_[ch].begin());
}
LimitLowFrequencyGains(gain);
// Use conservative high-frequency gains during clock-drift or when not in
// dominant nearend.
if (!dominant_nearend_detector_->IsNearendState() || clock_drift ||
config_.suppressor.conservative_hf_suppression) {
LimitHighFrequencyGains(config_.suppressor.conservative_hf_suppression,
gain);
}
// Store computed gains.
std::copy(gain->begin(), gain->end(), last_gain_.begin());
// Transform gains to amplitude domain.
aec3::VectorMath(optimization_).Sqrt(*gain);
}
SuppressionGain::SuppressionGain(const EchoCanceller3Config& config,
Aec3Optimization optimization,
int sample_rate_hz,
size_t num_capture_channels)
: data_dumper_(new ApmDataDumper(instance_count_.fetch_add(1) + 1)),
optimization_(optimization),
config_(config),
num_capture_channels_(num_capture_channels),
state_change_duration_blocks_(
static_cast<int>(config_.filter.config_change_duration_blocks)),
last_nearend_(num_capture_channels_, {0}),
last_echo_(num_capture_channels_, {0}),
nearend_smoothers_(
num_capture_channels_,
aec3::MovingAverage(kFftLengthBy2Plus1,
config.suppressor.nearend_average_blocks)),
nearend_params_(config_.suppressor.last_lf_band,
config_.suppressor.first_hf_band,
config_.suppressor.nearend_tuning),
normal_params_(config_.suppressor.last_lf_band,
config_.suppressor.first_hf_band,
config_.suppressor.normal_tuning),
use_unbounded_echo_spectrum_(config.suppressor.dominant_nearend_detection
.use_unbounded_echo_spectrum) {
RTC_DCHECK_LT(0, state_change_duration_blocks_);
last_gain_.fill(1.f);
if (config_.suppressor.use_subband_nearend_detection) {
dominant_nearend_detector_ = std::make_unique<SubbandNearendDetector>(
config_.suppressor.subband_nearend_detection, num_capture_channels_);
} else {
dominant_nearend_detector_ = std::make_unique<DominantNearendDetector>(
config_.suppressor.dominant_nearend_detection, num_capture_channels_);
}
RTC_DCHECK(dominant_nearend_detector_);
}
SuppressionGain::~SuppressionGain() = default;
void SuppressionGain::GetGain(
rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>>
nearend_spectrum,
rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>> echo_spectrum,
rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>>
residual_echo_spectrum,
rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>>
residual_echo_spectrum_unbounded,
rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>>
comfort_noise_spectrum,
const RenderSignalAnalyzer& render_signal_analyzer,
const AecState& aec_state,
const Block& render,
bool clock_drift,
float* high_bands_gain,
std::array<float, kFftLengthBy2Plus1>* low_band_gain) {
RTC_DCHECK(high_bands_gain);
RTC_DCHECK(low_band_gain);
// Choose residual echo spectrum for dominant nearend detection.
const auto echo = use_unbounded_echo_spectrum_
? residual_echo_spectrum_unbounded
: residual_echo_spectrum;
// Update the nearend state selection.
dominant_nearend_detector_->Update(nearend_spectrum, echo,
comfort_noise_spectrum, initial_state_);
// Compute gain for the lower band.
bool low_noise_render = low_render_detector_.Detect(render);
LowerBandGain(low_noise_render, aec_state, nearend_spectrum,
residual_echo_spectrum, comfort_noise_spectrum, clock_drift,
low_band_gain);
// Compute the gain for the upper bands.
const std::optional<int> narrow_peak_band =
render_signal_analyzer.NarrowPeakBand();
*high_bands_gain =
UpperBandsGain(echo_spectrum, comfort_noise_spectrum, narrow_peak_band,
aec_state.SaturatedEcho(), render, *low_band_gain);
data_dumper_->DumpRaw("aec3_dominant_nearend",
dominant_nearend_detector_->IsNearendState());
}
void SuppressionGain::SetInitialState(bool state) {
initial_state_ = state;
if (state) {
initial_state_change_counter_ = state_change_duration_blocks_;
} else {
initial_state_change_counter_ = 0;
}
}
// Detects when the render signal can be considered to have low power and
// consist of stationary noise.
bool SuppressionGain::LowNoiseRenderDetector::Detect(const Block& render) {
float x2_sum = 0.f;
float x2_max = 0.f;
for (int ch = 0; ch < render.NumChannels(); ++ch) {
for (float x_k : render.View(/*band=*/0, ch)) {
const float x2 = x_k * x_k;
x2_sum += x2;
x2_max = std::max(x2_max, x2);
}
}
x2_sum = x2_sum / render.NumChannels();
constexpr float kThreshold = 50.f * 50.f * 64.f;
const bool low_noise_render =
average_power_ < kThreshold && x2_max < 3 * average_power_;
average_power_ = average_power_ * 0.9f + x2_sum * 0.1f;
return low_noise_render;
}
SuppressionGain::GainParameters::GainParameters(
int last_lf_band,
int first_hf_band,
const EchoCanceller3Config::Suppressor::Tuning& tuning)
: max_inc_factor(tuning.max_inc_factor),
max_dec_factor_lf(tuning.max_dec_factor_lf) {
// Compute per-band masking thresholds.
RTC_DCHECK_LT(last_lf_band, first_hf_band);
auto& lf = tuning.mask_lf;
auto& hf = tuning.mask_hf;
RTC_DCHECK_LT(lf.enr_transparent, lf.enr_suppress);
RTC_DCHECK_LT(hf.enr_transparent, hf.enr_suppress);
for (int k = 0; k < static_cast<int>(kFftLengthBy2Plus1); k++) {
float a;
if (k <= last_lf_band) {
a = 0.f;
} else if (k < first_hf_band) {
a = (k - last_lf_band) / static_cast<float>(first_hf_band - last_lf_band);
} else {
a = 1.f;
}
enr_transparent_[k] = (1 - a) * lf.enr_transparent + a * hf.enr_transparent;
enr_suppress_[k] = (1 - a) * lf.enr_suppress + a * hf.enr_suppress;
emr_transparent_[k] = (1 - a) * lf.emr_transparent + a * hf.emr_transparent;
}
}
} // namespace webrtc