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webrtc/modules/audio_processing/aec3/echo_remover.cc
Gustaf Ullberg a63d152423 AEC3: Unbounded echo spectrum for dominant nearend detection. 
The dominant nearend detector uses the residual echo spectrum for
determining whether in nearend state. The residual echo spectrum in
computed using the ERLE. To reduce the risk of echo leaks in the
suppressor, the ERLE is capped. While minimizing echo leaks, the
capping of the ERLE can affect the dominant nearend classification
negatively as the residual echo spectrum is often over estimated.

This change enables the dominant nearend detector to use a residual
echo spectrum computed with a virtually non-capped ERLE. This ERLE
is only used for dominant nearend detection and leads to increased
transparency.

The feature is currently disabled by default and can be enabled
with the field trial "WebRTC-Aec3UseUnboundedEchoSpectrum".

Bug: webrtc:12870
Change-Id: Icb675c6f5d42ab9286e623b5fb38424d5c9cbee4
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/221920
Reviewed-by: Jesus de Vicente Pena <devicentepena@webrtc.org>
Commit-Queue: Gustaf Ullberg <gustaf@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34270}
2021-06-11 13:30:00 +00:00

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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/echo_remover.h"
#include <math.h>
#include <stddef.h>
#include <algorithm>
#include <array>
#include <cmath>
#include <memory>
#include "api/array_view.h"
#include "modules/audio_processing/aec3/aec3_common.h"
#include "modules/audio_processing/aec3/aec3_fft.h"
#include "modules/audio_processing/aec3/aec_state.h"
#include "modules/audio_processing/aec3/comfort_noise_generator.h"
#include "modules/audio_processing/aec3/echo_path_variability.h"
#include "modules/audio_processing/aec3/echo_remover_metrics.h"
#include "modules/audio_processing/aec3/fft_data.h"
#include "modules/audio_processing/aec3/render_buffer.h"
#include "modules/audio_processing/aec3/render_signal_analyzer.h"
#include "modules/audio_processing/aec3/residual_echo_estimator.h"
#include "modules/audio_processing/aec3/subtractor.h"
#include "modules/audio_processing/aec3/subtractor_output.h"
#include "modules/audio_processing/aec3/suppression_filter.h"
#include "modules/audio_processing/aec3/suppression_gain.h"
#include "modules/audio_processing/logging/apm_data_dumper.h"
#include "rtc_base/atomic_ops.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
namespace webrtc {
namespace {
// Maximum number of channels for which the capture channel data is stored on
// the stack. If the number of channels are larger than this, they are stored
// using scratch memory that is pre-allocated on the heap. The reason for this
// partitioning is not to waste heap space for handling the more common numbers
// of channels, while at the same time not limiting the support for higher
// numbers of channels by enforcing the capture channel data to be stored on the
// stack using a fixed maximum value.
constexpr size_t kMaxNumChannelsOnStack = 2;
// Chooses the number of channels to store on the heap when that is required due
// to the number of capture channels being larger than the pre-defined number
// of channels to store on the stack.
size_t NumChannelsOnHeap(size_t num_capture_channels) {
return num_capture_channels > kMaxNumChannelsOnStack ? num_capture_channels
: 0;
}
void LinearEchoPower(const FftData& E,
const FftData& Y,
std::array<float, kFftLengthBy2Plus1>* S2) {
for (size_t k = 0; k < E.re.size(); ++k) {
(*S2)[k] = (Y.re[k] - E.re[k]) * (Y.re[k] - E.re[k]) +
(Y.im[k] - E.im[k]) * (Y.im[k] - E.im[k]);
}
}
// Fades between two input signals using a fix-sized transition.
void SignalTransition(rtc::ArrayView<const float> from,
rtc::ArrayView<const float> to,
rtc::ArrayView<float> out) {
if (from == to) {
RTC_DCHECK_EQ(to.size(), out.size());
std::copy(to.begin(), to.end(), out.begin());
} else {
constexpr size_t kTransitionSize = 30;
constexpr float kOneByTransitionSizePlusOne = 1.f / (kTransitionSize + 1);
RTC_DCHECK_EQ(from.size(), to.size());
RTC_DCHECK_EQ(from.size(), out.size());
RTC_DCHECK_LE(kTransitionSize, out.size());
for (size_t k = 0; k < kTransitionSize; ++k) {
float a = (k + 1) * kOneByTransitionSizePlusOne;
out[k] = a * to[k] + (1.f - a) * from[k];
}
std::copy(to.begin() + kTransitionSize, to.end(),
out.begin() + kTransitionSize);
}
}
// Computes a windowed (square root Hanning) padded FFT and updates the related
// memory.
void WindowedPaddedFft(const Aec3Fft& fft,
rtc::ArrayView<const float> v,
rtc::ArrayView<float> v_old,
FftData* V) {
fft.PaddedFft(v, v_old, Aec3Fft::Window::kSqrtHanning, V);
std::copy(v.begin(), v.end(), v_old.begin());
}
// Class for removing the echo from the capture signal.
class EchoRemoverImpl final : public EchoRemover {
public:
EchoRemoverImpl(const EchoCanceller3Config& config,
int sample_rate_hz,
size_t num_render_channels,
size_t num_capture_channels);
~EchoRemoverImpl() override;
EchoRemoverImpl(const EchoRemoverImpl&) = delete;
EchoRemoverImpl& operator=(const EchoRemoverImpl&) = delete;
void GetMetrics(EchoControl::Metrics* metrics) const override;
// Removes the echo from a block of samples from the capture signal. The
// supplied render signal is assumed to be pre-aligned with the capture
// signal.
void ProcessCapture(
EchoPathVariability echo_path_variability,
bool capture_signal_saturation,
const absl::optional<DelayEstimate>& external_delay,
RenderBuffer* render_buffer,
std::vector<std::vector<std::vector<float>>>* linear_output,
std::vector<std::vector<std::vector<float>>>* capture) override;
// Updates the status on whether echo leakage is detected in the output of the
// echo remover.
void UpdateEchoLeakageStatus(bool leakage_detected) override {
echo_leakage_detected_ = leakage_detected;
}
void SetCaptureOutputUsage(bool capture_output_used) override {
capture_output_used_ = capture_output_used;
}
private:
// Selects which of the coarse and refined linear filter outputs that is most
// appropriate to pass to the suppressor and forms the linear filter output by
// smoothly transition between those.
void FormLinearFilterOutput(const SubtractorOutput& subtractor_output,
rtc::ArrayView<float> output);
static int instance_count_;
const EchoCanceller3Config config_;
const Aec3Fft fft_;
std::unique_ptr<ApmDataDumper> data_dumper_;
const Aec3Optimization optimization_;
const int sample_rate_hz_;
const size_t num_render_channels_;
const size_t num_capture_channels_;
const bool use_coarse_filter_output_;
Subtractor subtractor_;
SuppressionGain suppression_gain_;
ComfortNoiseGenerator cng_;
SuppressionFilter suppression_filter_;
RenderSignalAnalyzer render_signal_analyzer_;
ResidualEchoEstimator residual_echo_estimator_;
bool echo_leakage_detected_ = false;
bool capture_output_used_ = true;
AecState aec_state_;
EchoRemoverMetrics metrics_;
std::vector<std::array<float, kFftLengthBy2>> e_old_;
std::vector<std::array<float, kFftLengthBy2>> y_old_;
size_t block_counter_ = 0;
int gain_change_hangover_ = 0;
bool refined_filter_output_last_selected_ = true;
std::vector<std::array<float, kFftLengthBy2>> e_heap_;
std::vector<std::array<float, kFftLengthBy2Plus1>> Y2_heap_;
std::vector<std::array<float, kFftLengthBy2Plus1>> E2_heap_;
std::vector<std::array<float, kFftLengthBy2Plus1>> R2_heap_;
std::vector<std::array<float, kFftLengthBy2Plus1>> R2_unbounded_heap_;
std::vector<std::array<float, kFftLengthBy2Plus1>> S2_linear_heap_;
std::vector<FftData> Y_heap_;
std::vector<FftData> E_heap_;
std::vector<FftData> comfort_noise_heap_;
std::vector<FftData> high_band_comfort_noise_heap_;
std::vector<SubtractorOutput> subtractor_output_heap_;
};
int EchoRemoverImpl::instance_count_ = 0;
EchoRemoverImpl::EchoRemoverImpl(const EchoCanceller3Config& config,
int sample_rate_hz,
size_t num_render_channels,
size_t num_capture_channels)
: config_(config),
fft_(),
data_dumper_(
new ApmDataDumper(rtc::AtomicOps::Increment(&instance_count_))),
optimization_(DetectOptimization()),
sample_rate_hz_(sample_rate_hz),
num_render_channels_(num_render_channels),
num_capture_channels_(num_capture_channels),
use_coarse_filter_output_(
config_.filter.enable_coarse_filter_output_usage),
subtractor_(config,
num_render_channels_,
num_capture_channels_,
data_dumper_.get(),
optimization_),
suppression_gain_(config_,
optimization_,
sample_rate_hz,
num_capture_channels),
cng_(config_, optimization_, num_capture_channels_),
suppression_filter_(optimization_,
sample_rate_hz_,
num_capture_channels_),
render_signal_analyzer_(config_),
residual_echo_estimator_(config_, num_render_channels),
aec_state_(config_, num_capture_channels_),
e_old_(num_capture_channels_, {0.f}),
y_old_(num_capture_channels_, {0.f}),
e_heap_(NumChannelsOnHeap(num_capture_channels_), {0.f}),
Y2_heap_(NumChannelsOnHeap(num_capture_channels_)),
E2_heap_(NumChannelsOnHeap(num_capture_channels_)),
R2_heap_(NumChannelsOnHeap(num_capture_channels_)),
R2_unbounded_heap_(NumChannelsOnHeap(num_capture_channels_)),
S2_linear_heap_(NumChannelsOnHeap(num_capture_channels_)),
Y_heap_(NumChannelsOnHeap(num_capture_channels_)),
E_heap_(NumChannelsOnHeap(num_capture_channels_)),
comfort_noise_heap_(NumChannelsOnHeap(num_capture_channels_)),
high_band_comfort_noise_heap_(NumChannelsOnHeap(num_capture_channels_)),
subtractor_output_heap_(NumChannelsOnHeap(num_capture_channels_)) {
RTC_DCHECK(ValidFullBandRate(sample_rate_hz));
}
EchoRemoverImpl::~EchoRemoverImpl() = default;
void EchoRemoverImpl::GetMetrics(EchoControl::Metrics* metrics) const {
// Echo return loss (ERL) is inverted to go from gain to attenuation.
metrics->echo_return_loss = -10.0 * std::log10(aec_state_.ErlTimeDomain());
metrics->echo_return_loss_enhancement =
Log2TodB(aec_state_.FullBandErleLog2());
}
void EchoRemoverImpl::ProcessCapture(
EchoPathVariability echo_path_variability,
bool capture_signal_saturation,
const absl::optional<DelayEstimate>& external_delay,
RenderBuffer* render_buffer,
std::vector<std::vector<std::vector<float>>>* linear_output,
std::vector<std::vector<std::vector<float>>>* capture) {
++block_counter_;
const std::vector<std::vector<std::vector<float>>>& x =
render_buffer->Block(0);
std::vector<std::vector<std::vector<float>>>* y = capture;
RTC_DCHECK(render_buffer);
RTC_DCHECK(y);
RTC_DCHECK_EQ(x.size(), NumBandsForRate(sample_rate_hz_));
RTC_DCHECK_EQ(y->size(), NumBandsForRate(sample_rate_hz_));
RTC_DCHECK_EQ(x[0].size(), num_render_channels_);
RTC_DCHECK_EQ((*y)[0].size(), num_capture_channels_);
RTC_DCHECK_EQ(x[0][0].size(), kBlockSize);
RTC_DCHECK_EQ((*y)[0][0].size(), kBlockSize);
// Stack allocated data to use when the number of channels is low.
std::array<std::array<float, kFftLengthBy2>, kMaxNumChannelsOnStack> e_stack;
std::array<std::array<float, kFftLengthBy2Plus1>, kMaxNumChannelsOnStack>
Y2_stack;
std::array<std::array<float, kFftLengthBy2Plus1>, kMaxNumChannelsOnStack>
E2_stack;
std::array<std::array<float, kFftLengthBy2Plus1>, kMaxNumChannelsOnStack>
R2_stack;
std::array<std::array<float, kFftLengthBy2Plus1>, kMaxNumChannelsOnStack>
R2_unbounded_stack;
std::array<std::array<float, kFftLengthBy2Plus1>, kMaxNumChannelsOnStack>
S2_linear_stack;
std::array<FftData, kMaxNumChannelsOnStack> Y_stack;
std::array<FftData, kMaxNumChannelsOnStack> E_stack;
std::array<FftData, kMaxNumChannelsOnStack> comfort_noise_stack;
std::array<FftData, kMaxNumChannelsOnStack> high_band_comfort_noise_stack;
std::array<SubtractorOutput, kMaxNumChannelsOnStack> subtractor_output_stack;
rtc::ArrayView<std::array<float, kFftLengthBy2>> e(e_stack.data(),
num_capture_channels_);
rtc::ArrayView<std::array<float, kFftLengthBy2Plus1>> Y2(
Y2_stack.data(), num_capture_channels_);
rtc::ArrayView<std::array<float, kFftLengthBy2Plus1>> E2(
E2_stack.data(), num_capture_channels_);
rtc::ArrayView<std::array<float, kFftLengthBy2Plus1>> R2(
R2_stack.data(), num_capture_channels_);
rtc::ArrayView<std::array<float, kFftLengthBy2Plus1>> R2_unbounded(
R2_unbounded_stack.data(), num_capture_channels_);
rtc::ArrayView<std::array<float, kFftLengthBy2Plus1>> S2_linear(
S2_linear_stack.data(), num_capture_channels_);
rtc::ArrayView<FftData> Y(Y_stack.data(), num_capture_channels_);
rtc::ArrayView<FftData> E(E_stack.data(), num_capture_channels_);
rtc::ArrayView<FftData> comfort_noise(comfort_noise_stack.data(),
num_capture_channels_);
rtc::ArrayView<FftData> high_band_comfort_noise(
high_band_comfort_noise_stack.data(), num_capture_channels_);
rtc::ArrayView<SubtractorOutput> subtractor_output(
subtractor_output_stack.data(), num_capture_channels_);
if (NumChannelsOnHeap(num_capture_channels_) > 0) {
// If the stack-allocated space is too small, use the heap for storing the
// microphone data.
e = rtc::ArrayView<std::array<float, kFftLengthBy2>>(e_heap_.data(),
num_capture_channels_);
Y2 = rtc::ArrayView<std::array<float, kFftLengthBy2Plus1>>(
Y2_heap_.data(), num_capture_channels_);
E2 = rtc::ArrayView<std::array<float, kFftLengthBy2Plus1>>(
E2_heap_.data(), num_capture_channels_);
R2 = rtc::ArrayView<std::array<float, kFftLengthBy2Plus1>>(
R2_heap_.data(), num_capture_channels_);
R2_unbounded = rtc::ArrayView<std::array<float, kFftLengthBy2Plus1>>(
R2_unbounded_heap_.data(), num_capture_channels_);
S2_linear = rtc::ArrayView<std::array<float, kFftLengthBy2Plus1>>(
S2_linear_heap_.data(), num_capture_channels_);
Y = rtc::ArrayView<FftData>(Y_heap_.data(), num_capture_channels_);
E = rtc::ArrayView<FftData>(E_heap_.data(), num_capture_channels_);
comfort_noise = rtc::ArrayView<FftData>(comfort_noise_heap_.data(),
num_capture_channels_);
high_band_comfort_noise = rtc::ArrayView<FftData>(
high_band_comfort_noise_heap_.data(), num_capture_channels_);
subtractor_output = rtc::ArrayView<SubtractorOutput>(
subtractor_output_heap_.data(), num_capture_channels_);
}
data_dumper_->DumpWav("aec3_echo_remover_capture_input", kBlockSize,
&(*y)[0][0][0], 16000, 1);
data_dumper_->DumpWav("aec3_echo_remover_render_input", kBlockSize,
&x[0][0][0], 16000, 1);
data_dumper_->DumpRaw("aec3_echo_remover_capture_input", (*y)[0][0]);
data_dumper_->DumpRaw("aec3_echo_remover_render_input", x[0][0]);
aec_state_.UpdateCaptureSaturation(capture_signal_saturation);
if (echo_path_variability.AudioPathChanged()) {
// Ensure that the gain change is only acted on once per frame.
if (echo_path_variability.gain_change) {
if (gain_change_hangover_ == 0) {
constexpr int kMaxBlocksPerFrame = 3;
gain_change_hangover_ = kMaxBlocksPerFrame;
rtc::LoggingSeverity log_level =
config_.delay.log_warning_on_delay_changes ? rtc::LS_WARNING
: rtc::LS_VERBOSE;
RTC_LOG_V(log_level)
<< "Gain change detected at block " << block_counter_;
} else {
echo_path_variability.gain_change = false;
}
}
subtractor_.HandleEchoPathChange(echo_path_variability);
aec_state_.HandleEchoPathChange(echo_path_variability);
if (echo_path_variability.delay_change !=
EchoPathVariability::DelayAdjustment::kNone) {
suppression_gain_.SetInitialState(true);
}
}
if (gain_change_hangover_ > 0) {
--gain_change_hangover_;
}
// Analyze the render signal.
render_signal_analyzer_.Update(*render_buffer,
aec_state_.MinDirectPathFilterDelay());
// State transition.
if (aec_state_.TransitionTriggered()) {
subtractor_.ExitInitialState();
suppression_gain_.SetInitialState(false);
}
// Perform linear echo cancellation.
subtractor_.Process(*render_buffer, (*y)[0], render_signal_analyzer_,
aec_state_, subtractor_output);
// Compute spectra.
for (size_t ch = 0; ch < num_capture_channels_; ++ch) {
FormLinearFilterOutput(subtractor_output[ch], e[ch]);
WindowedPaddedFft(fft_, (*y)[0][ch], y_old_[ch], &Y[ch]);
WindowedPaddedFft(fft_, e[ch], e_old_[ch], &E[ch]);
LinearEchoPower(E[ch], Y[ch], &S2_linear[ch]);
Y[ch].Spectrum(optimization_, Y2[ch]);
E[ch].Spectrum(optimization_, E2[ch]);
}
// Optionally return the linear filter output.
if (linear_output) {
RTC_DCHECK_GE(1, linear_output->size());
RTC_DCHECK_EQ(num_capture_channels_, linear_output[0].size());
for (size_t ch = 0; ch < num_capture_channels_; ++ch) {
RTC_DCHECK_EQ(kBlockSize, (*linear_output)[0][ch].size());
std::copy(e[ch].begin(), e[ch].end(), (*linear_output)[0][ch].begin());
}
}
// Update the AEC state information.
aec_state_.Update(external_delay, subtractor_.FilterFrequencyResponses(),
subtractor_.FilterImpulseResponses(), *render_buffer, E2,
Y2, subtractor_output);
// Choose the linear output.
const auto& Y_fft = aec_state_.UseLinearFilterOutput() ? E : Y;
data_dumper_->DumpWav("aec3_output_linear", kBlockSize, &(*y)[0][0][0], 16000,
1);
data_dumper_->DumpWav("aec3_output_linear2", kBlockSize, &e[0][0], 16000, 1);
// Estimate the comfort noise.
cng_.Compute(aec_state_.SaturatedCapture(), Y2, comfort_noise,
high_band_comfort_noise);
// Only do the below processing if the output of the audio processing module
// is used.
std::array<float, kFftLengthBy2Plus1> G;
if (capture_output_used_) {
// Estimate the residual echo power.
residual_echo_estimator_.Estimate(aec_state_, *render_buffer, S2_linear, Y2,
suppression_gain_.IsDominantNearend(), R2,
R2_unbounded);
// Suppressor nearend estimate.
if (aec_state_.UsableLinearEstimate()) {
// E2 is bound by Y2.
for (size_t ch = 0; ch < num_capture_channels_; ++ch) {
std::transform(E2[ch].begin(), E2[ch].end(), Y2[ch].begin(),
E2[ch].begin(),
[](float a, float b) { return std::min(a, b); });
}
}
const auto& nearend_spectrum = aec_state_.UsableLinearEstimate() ? E2 : Y2;
// Suppressor echo estimate.
const auto& echo_spectrum =
aec_state_.UsableLinearEstimate() ? S2_linear : R2;
// Determine if the suppressor should assume clock drift.
const bool clock_drift = config_.echo_removal_control.has_clock_drift ||
echo_path_variability.clock_drift;
// Compute preferred gains.
float high_bands_gain;
suppression_gain_.GetGain(nearend_spectrum, echo_spectrum, R2, R2_unbounded,
cng_.NoiseSpectrum(), render_signal_analyzer_,
aec_state_, x, clock_drift, &high_bands_gain, &G);
suppression_filter_.ApplyGain(comfort_noise, high_band_comfort_noise, G,
high_bands_gain, Y_fft, y);
} else {
G.fill(0.f);
}
// Update the metrics.
metrics_.Update(aec_state_, cng_.NoiseSpectrum()[0], G);
// Debug outputs for the purpose of development and analysis.
data_dumper_->DumpWav("aec3_echo_estimate", kBlockSize,
&subtractor_output[0].s_refined[0], 16000, 1);
data_dumper_->DumpRaw("aec3_output", (*y)[0][0]);
data_dumper_->DumpRaw("aec3_narrow_render",
render_signal_analyzer_.NarrowPeakBand() ? 1 : 0);
data_dumper_->DumpRaw("aec3_N2", cng_.NoiseSpectrum()[0]);
data_dumper_->DumpRaw("aec3_suppressor_gain", G);
data_dumper_->DumpWav("aec3_output",
rtc::ArrayView<const float>(&(*y)[0][0][0], kBlockSize),
16000, 1);
data_dumper_->DumpRaw("aec3_using_subtractor_output[0]",
aec_state_.UseLinearFilterOutput() ? 1 : 0);
data_dumper_->DumpRaw("aec3_E2", E2[0]);
data_dumper_->DumpRaw("aec3_S2_linear", S2_linear[0]);
data_dumper_->DumpRaw("aec3_Y2", Y2[0]);
data_dumper_->DumpRaw(
"aec3_X2", render_buffer->Spectrum(
aec_state_.MinDirectPathFilterDelay())[/*channel=*/0]);
data_dumper_->DumpRaw("aec3_R2", R2[0]);
data_dumper_->DumpRaw("aec3_filter_delay",
aec_state_.MinDirectPathFilterDelay());
data_dumper_->DumpRaw("aec3_capture_saturation",
aec_state_.SaturatedCapture() ? 1 : 0);
}
void EchoRemoverImpl::FormLinearFilterOutput(
const SubtractorOutput& subtractor_output,
rtc::ArrayView<float> output) {
RTC_DCHECK_EQ(subtractor_output.e_refined.size(), output.size());
RTC_DCHECK_EQ(subtractor_output.e_coarse.size(), output.size());
bool use_refined_output = true;
if (use_coarse_filter_output_) {
// As the output of the refined adaptive filter generally should be better
// than the coarse filter output, add a margin and threshold for when
// choosing the coarse filter output.
if (subtractor_output.e2_coarse < 0.9f * subtractor_output.e2_refined &&
subtractor_output.y2 > 30.f * 30.f * kBlockSize &&
(subtractor_output.s2_refined > 60.f * 60.f * kBlockSize ||
subtractor_output.s2_coarse > 60.f * 60.f * kBlockSize)) {
use_refined_output = false;
} else {
// If the refined filter is diverged, choose the filter output that has
// the lowest power.
if (subtractor_output.e2_coarse < subtractor_output.e2_refined &&
subtractor_output.y2 < subtractor_output.e2_refined) {
use_refined_output = false;
}
}
}
SignalTransition(refined_filter_output_last_selected_
? subtractor_output.e_refined
: subtractor_output.e_coarse,
use_refined_output ? subtractor_output.e_refined
: subtractor_output.e_coarse,
output);
refined_filter_output_last_selected_ = use_refined_output;
}
} // namespace
EchoRemover* EchoRemover::Create(const EchoCanceller3Config& config,
int sample_rate_hz,
size_t num_render_channels,
size_t num_capture_channels) {
return new EchoRemoverImpl(config, sample_rate_hz, num_render_channels,
num_capture_channels);
}
} // namespace webrtc
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