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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 <stddef.h>
#include <array>
#include <memory>
#include <vector>
#include "absl/types/optional.h"
#include "api/array_view.h"
#include "api/audio/echo_canceller3_config.h"
#include "modules/audio_processing/aec3/aec3_common.h"
#include "modules/audio_processing/aec3/delay_estimate.h"
#include "modules/audio_processing/aec3/echo_audibility.h"
#include "modules/audio_processing/aec3/echo_path_variability.h"
#include "modules/audio_processing/aec3/erl_estimator.h"
#include "modules/audio_processing/aec3/erle_estimator.h"
#include "modules/audio_processing/aec3/filter_analyzer.h"
#include "modules/audio_processing/aec3/render_buffer.h"
#include "modules/audio_processing/aec3/reverb_model_estimator.h"
#include "modules/audio_processing/aec3/subtractor_output.h"
#include "modules/audio_processing/aec3/subtractor_output_analyzer.h"
namespace webrtc {
class ApmDataDumper;
// Handles the state and the conditions for the echo removal functionality.
class AecState {
AecState(const EchoCanceller3Config& config, size_t num_capture_channels);
// Returns whether the echo subtractor can be used to determine the residual
// echo.
bool UsableLinearEstimate() const {
return filter_quality_state_.LinearFilterUsable() &&
// Returns whether the echo subtractor output should be used as output.
bool UseLinearFilterOutput() const {
return filter_quality_state_.LinearFilterUsable() &&
// Returns whether the render signal is currently active.
bool ActiveRender() const { return blocks_with_active_render_ > 200; }
// Returns the appropriate scaling of the residual echo to match the
// audibility.
void GetResidualEchoScaling(rtc::ArrayView<float> residual_scaling) const;
// Returns whether the stationary properties of the signals are used in the
// aec.
bool UseStationarityProperties() const {
return config_.echo_audibility.use_stationarity_properties;
// Returns the ERLE.
rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>> Erle() const {
return erle_estimator_.Erle();
// Returns an offset to apply to the estimation of the residual echo
// computation. Returning nullopt means that no offset should be used, while
// any other value will be applied as a multiplier to the estimated residual
// echo.
absl::optional<float> ErleUncertainty() const;
// Returns the fullband ERLE estimate in log2 units.
float FullBandErleLog2() const { return erle_estimator_.FullbandErleLog2(); }
// Returns the ERL.
const std::array<float, kFftLengthBy2Plus1>& Erl() const {
return erl_estimator_.Erl();
// Returns the time-domain ERL.
float ErlTimeDomain() const { return erl_estimator_.ErlTimeDomain(); }
// Returns the delay estimate based on the linear filter.
int MinDirectPathFilterDelay() const {
return delay_state_.MinDirectPathFilterDelay();
// Returns whether the capture signal is saturated.
bool SaturatedCapture() const { return capture_signal_saturation_; }
// Returns whether the echo signal is saturated.
bool SaturatedEcho() const { return saturation_detector_.SaturatedEcho(); }
// Updates the capture signal saturation.
void UpdateCaptureSaturation(bool capture_signal_saturation) {
capture_signal_saturation_ = capture_signal_saturation;
// Returns whether the transparent mode is active
bool TransparentMode() const {
return transparent_mode_activated_ && transparent_state_.Active();
// Takes appropriate action at an echo path change.
void HandleEchoPathChange(const EchoPathVariability& echo_path_variability);
// Returns the decay factor for the echo reverberation.
float ReverbDecay() const { return reverb_model_estimator_.ReverbDecay(); }
// Return the frequency response of the reverberant echo.
rtc::ArrayView<const float> GetReverbFrequencyResponse() const {
return reverb_model_estimator_.GetReverbFrequencyResponse();
// Returns whether the transition for going out of the initial stated has
// been triggered.
bool TransitionTriggered() const {
return initial_state_.TransitionTriggered();
// Updates the aec state.
// TODO( Compute multi-channel ERL.
void Update(
const absl::optional<DelayEstimate>& external_delay,
rtc::ArrayView<const std::vector<std::array<float, kFftLengthBy2Plus1>>>
rtc::ArrayView<const std::vector<float>>
const RenderBuffer& render_buffer,
rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>> E2_refined,
rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>> Y2,
rtc::ArrayView<const SubtractorOutput> subtractor_output);
// Returns filter length in blocks.
int FilterLengthBlocks() const {
// All filters have the same length, so arbitrarily return channel 0 length.
return filter_analyzer_.FilterLengthBlocks();
static int instance_count_;
std::unique_ptr<ApmDataDumper> data_dumper_;
const EchoCanceller3Config config_;
const size_t num_capture_channels_;
const bool transparent_mode_activated_;
const bool deactivate_initial_state_reset_at_echo_path_change_;
const bool full_reset_at_echo_path_change_;
const bool subtractor_analyzer_reset_at_echo_path_change_;
// Class for controlling the transition from the intial state, which in turn
// controls when the filter parameters for the initial state should be used.
class InitialState {
explicit InitialState(const EchoCanceller3Config& config);
// Resets the state to again begin in the initial state.
void Reset();
// Updates the state based on new data.
void Update(bool active_render, bool saturated_capture);
// Returns whether the initial state is active or not.
bool InitialStateActive() const { return initial_state_; }
// Returns that the transition from the initial state has was started.
bool TransitionTriggered() const { return transition_triggered_; }
const bool conservative_initial_phase_;
const float initial_state_seconds_;
bool transition_triggered_ = false;
bool initial_state_ = true;
size_t strong_not_saturated_render_blocks_ = 0;
} initial_state_;
// Class for choosing the direct-path delay relative to the beginning of the
// filter, as well as any other data related to the delay used within
// AecState.
class FilterDelay {
FilterDelay(const EchoCanceller3Config& config,
size_t num_capture_channels);
// Returns whether an external delay has been reported to the AecState (from
// the delay estimator).
bool ExternalDelayReported() const { return external_delay_reported_; }
// Returns the delay in blocks relative to the beginning of the filter that
// corresponds to the direct path of the echo.
rtc::ArrayView<const int> DirectPathFilterDelays() const {
return filter_delays_blocks_;
// Returns the minimum delay among the direct path delays relative to the
// beginning of the filter
int MinDirectPathFilterDelay() const { return min_filter_delay_; }
// Updates the delay estimates based on new data.
void Update(
rtc::ArrayView<const int> analyzer_filter_delay_estimates_blocks,
const absl::optional<DelayEstimate>& external_delay,
size_t blocks_with_proper_filter_adaptation);
const int delay_headroom_samples_;
bool external_delay_reported_ = false;
std::vector<int> filter_delays_blocks_;
int min_filter_delay_ = 0;
absl::optional<DelayEstimate> external_delay_;
} delay_state_;
// Class for detecting and toggling the transparent mode which causes the
// suppressor to apply no suppression.
class TransparentMode {
explicit TransparentMode(const EchoCanceller3Config& config);
// Returns whether the transparent mode should be active.
bool Active() const { return transparency_activated_; }
// Resets the state of the detector.
void Reset();
// Updates the detection deciscion based on new data.
void Update(int filter_delay_blocks,
bool any_filter_consistent,
bool any_filter_converged,
bool all_filters_diverged,
bool active_render,
bool saturated_capture);
const bool bounded_erl_;
const bool linear_and_stable_echo_path_;
size_t capture_block_counter_ = 0;
bool transparency_activated_ = false;
size_t active_blocks_since_sane_filter_;
bool sane_filter_observed_ = false;
bool finite_erl_recently_detected_ = false;
size_t non_converged_sequence_size_;
size_t diverged_sequence_size_ = 0;
size_t active_non_converged_sequence_size_ = 0;
size_t num_converged_blocks_ = 0;
bool recent_convergence_during_activity_ = false;
size_t strong_not_saturated_render_blocks_ = 0;
} transparent_state_;
// Class for analyzing how well the linear filter is, and can be expected to,
// perform on the current signals. The purpose of this is for using to
// select the echo suppression functionality as well as the input to the echo
// suppressor.
class FilteringQualityAnalyzer {
FilteringQualityAnalyzer(const EchoCanceller3Config& config,
size_t num_capture_channels);
// Returns whether the linear filter can be used for the echo
// canceller output.
bool LinearFilterUsable() const { return overall_usable_linear_estimates_; }
// Returns whether an individual filter output can be used for the echo
// canceller output.
const std::vector<bool>& UsableLinearFilterOutputs() const {
return usable_linear_filter_estimates_;
// Resets the state of the analyzer.
void Reset();
// Updates the analysis based on new data.
void Update(bool active_render,
bool transparent_mode,
bool saturated_capture,
const absl::optional<DelayEstimate>& external_delay,
bool any_filter_converged);
const bool use_linear_filter_;
bool overall_usable_linear_estimates_ = false;
size_t filter_update_blocks_since_reset_ = 0;
size_t filter_update_blocks_since_start_ = 0;
bool convergence_seen_ = false;
std::vector<bool> usable_linear_filter_estimates_;
} filter_quality_state_;
// Class for detecting whether the echo is to be considered to be
// saturated.
class SaturationDetector {
// Returns whether the echo is to be considered saturated.
bool SaturatedEcho() const { return saturated_echo_; }
// Updates the detection decision based on new data.
void Update(rtc::ArrayView<const std::vector<float>> x,
bool saturated_capture,
bool usable_linear_estimate,
rtc::ArrayView<const SubtractorOutput> subtractor_output,
float echo_path_gain);
bool saturated_echo_ = false;
} saturation_detector_;
ErlEstimator erl_estimator_;
ErleEstimator erle_estimator_;
size_t strong_not_saturated_render_blocks_ = 0;
size_t blocks_with_active_render_ = 0;
bool capture_signal_saturation_ = false;
FilterAnalyzer filter_analyzer_;
absl::optional<DelayEstimate> external_delay_;
EchoAudibility echo_audibility_;
ReverbModelEstimator reverb_model_estimator_;
ReverbModel avg_render_reverb_;
SubtractorOutputAnalyzer subtractor_output_analyzer_;
} // namespace webrtc