modules/audio_processing/aec3/transparent_mode.cc - src - Git at Google

 /*
  *  Copyright (c) 2020 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/transparent_mode.h"

 #include "rtc_base/checks.h"
 #include "system_wrappers/include/field_trial.h"

 namespace webrtc {
 namespace {

 constexpr size_t kBlocksSinceConvergencedFilterInit = 10000;
 constexpr size_t kBlocksSinceConsistentEstimateInit = 10000;

 bool DeactivateTransparentMode() {
   return field_trial::IsEnabled("WebRTC-Aec3TransparentModeKillSwitch");
 }

 bool DeactivateTransparentModeHmm() {
   return field_trial::IsEnabled("WebRTC-Aec3TransparentModeHmmKillSwitch");
 }

 }  // namespace

 // Classifier that toggles transparent mode which reduces echo suppression when
 // headsets are used.
 class TransparentModeImpl : public TransparentMode {
  public:
   bool Active() const override { return transparency_activated_; }

   void Reset() override {
     // Determines if transparent mode is used.
     transparency_activated_ = false;

     // The estimated probability of being transparent mode.
     prob_transparent_state_ = 0.f;
   }

   void Update(int filter_delay_blocks,
               bool any_filter_consistent,
               bool any_filter_converged,
               bool all_filters_diverged,
               bool active_render,
               bool saturated_capture) override {
     // The classifier is implemented as a Hidden Markov Model (HMM) with two
     // hidden states: "normal" and "transparent". The estimated probabilities of
     // the two states are updated by observing filter convergence during active
     // render. The filters are less likely to be reported as converged when
     // there is no echo present in the microphone signal.

     // The constants have been obtained by observing active_render and
     // any_filter_converged under varying call scenarios. They have further been
     // hand tuned to prefer normal state during uncertain regions (to avoid echo
     // leaks).

     // The model is only updated during active render.
     if (!active_render)
       return;

     // Probability of switching from one state to the other.
     constexpr float kSwitch = 0.000001f;

     // Probability of observing converged filters in states "normal" and
     // "transparent" during active render.
     constexpr float kConvergedNormal = 0.03f;
     constexpr float kConvergedTransparent = 0.005f;

     // Probability of transitioning to transparent state from normal state and
     // transparent state respectively.
     constexpr float kA[2] = {kSwitch, 1.f - kSwitch};

     // Probability of the two observations (converged filter or not converged
     // filter) in normal state and transparent state respectively.
     constexpr float kB[2][2] = {
         {1.f - kConvergedNormal, kConvergedNormal},
         {1.f - kConvergedTransparent, kConvergedTransparent}};

     // Probability of the two states before the update.
     const float prob_transparent = prob_transparent_state_;
     const float prob_normal = 1.f - prob_transparent;

     // Probability of transitioning to transparent state.
     const float prob_transition_transparent =
         prob_normal * kA[0] + prob_transparent * kA[1];
     const float prob_transition_normal = 1.f - prob_transition_transparent;

     // Observed output.
     const int out = any_filter_converged;

     // Joint probabilites of the observed output and respective states.
     const float prob_joint_normal = prob_transition_normal * kB[0][out];
     const float prob_joint_transparent =
         prob_transition_transparent * kB[1][out];

     // Conditional probability of transparent state and the observed output.
     RTC_DCHECK_GT(prob_joint_normal + prob_joint_transparent, 0.f);
     prob_transparent_state_ =
         prob_joint_transparent / (prob_joint_normal + prob_joint_transparent);

     // Transparent mode is only activated when its state probability is high.
     // Dead zone between activation/deactivation thresholds to avoid switching
     // back and forth.
     if (prob_transparent_state_ > 0.95f) {
       transparency_activated_ = true;
     } else if (prob_transparent_state_ < 0.5f) {
       transparency_activated_ = false;
     }
   }

  private:
   bool transparency_activated_ = false;
   float prob_transparent_state_ = 0.f;
 };

 // Legacy classifier for toggling transparent mode.
 class LegacyTransparentModeImpl : public TransparentMode {
  public:
   explicit LegacyTransparentModeImpl(const EchoCanceller3Config& config)
       : linear_and_stable_echo_path_(
             config.echo_removal_control.linear_and_stable_echo_path),
         active_blocks_since_sane_filter_(kBlocksSinceConsistentEstimateInit),
         non_converged_sequence_size_(kBlocksSinceConvergencedFilterInit) {}

   bool Active() const override { return transparency_activated_; }

   void Reset() override {
     non_converged_sequence_size_ = kBlocksSinceConvergencedFilterInit;
     diverged_sequence_size_ = 0;
     strong_not_saturated_render_blocks_ = 0;
     if (linear_and_stable_echo_path_) {
       recent_convergence_during_activity_ = false;
     }
   }

   void Update(int filter_delay_blocks,
               bool any_filter_consistent,
               bool any_filter_converged,
               bool all_filters_diverged,
               bool active_render,
               bool saturated_capture) override {
     ++capture_block_counter_;
     strong_not_saturated_render_blocks_ +=
         active_render && !saturated_capture ? 1 : 0;

     if (any_filter_consistent && filter_delay_blocks < 5) {
       sane_filter_observed_ = true;
       active_blocks_since_sane_filter_ = 0;
     } else if (active_render) {
       ++active_blocks_since_sane_filter_;
     }

     bool sane_filter_recently_seen;
     if (!sane_filter_observed_) {
       sane_filter_recently_seen =
           capture_block_counter_ <= 5 * kNumBlocksPerSecond;
     } else {
       sane_filter_recently_seen =
           active_blocks_since_sane_filter_ <= 30 * kNumBlocksPerSecond;
     }

     if (any_filter_converged) {
       recent_convergence_during_activity_ = true;
       active_non_converged_sequence_size_ = 0;
       non_converged_sequence_size_ = 0;
       ++num_converged_blocks_;
     } else {
       if (++non_converged_sequence_size_ > 20 * kNumBlocksPerSecond) {
         num_converged_blocks_ = 0;
       }

       if (active_render &&
           ++active_non_converged_sequence_size_ > 60 * kNumBlocksPerSecond) {
         recent_convergence_during_activity_ = false;
       }
     }

     if (!all_filters_diverged) {
       diverged_sequence_size_ = 0;
     } else if (++diverged_sequence_size_ >= 60) {
       // TODO(peah): Change these lines to ensure proper triggering of usable
       // filter.
       non_converged_sequence_size_ = kBlocksSinceConvergencedFilterInit;
     }

     if (active_non_converged_sequence_size_ > 60 * kNumBlocksPerSecond) {
       finite_erl_recently_detected_ = false;
     }
     if (num_converged_blocks_ > 50) {
       finite_erl_recently_detected_ = true;
     }

     if (finite_erl_recently_detected_) {
       transparency_activated_ = false;
     } else if (sane_filter_recently_seen &&
                recent_convergence_during_activity_) {
       transparency_activated_ = false;
     } else {
       const bool filter_should_have_converged =
           strong_not_saturated_render_blocks_ > 6 * kNumBlocksPerSecond;
       transparency_activated_ = filter_should_have_converged;
     }
   }

  private:
   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;
 };

 std::unique_ptr<TransparentMode> TransparentMode::Create(
     const EchoCanceller3Config& config) {
   if (config.ep_strength.bounded_erl || DeactivateTransparentMode()) {
     return nullptr;
   }
   if (DeactivateTransparentModeHmm()) {
     return std::make_unique<LegacyTransparentModeImpl>(config);
   }
   return std::make_unique<TransparentModeImpl>();
 }

 }  // namespace webrtc
	/*
	* Copyright (c) 2020 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/transparent_mode.h"

	#include "rtc_base/checks.h"
	#include "system_wrappers/include/field_trial.h"

	namespace webrtc {
	namespace {

	constexpr size_t kBlocksSinceConvergencedFilterInit = 10000;
	constexpr size_t kBlocksSinceConsistentEstimateInit = 10000;

	bool DeactivateTransparentMode() {
	return field_trial::IsEnabled("WebRTC-Aec3TransparentModeKillSwitch");
	}

	bool DeactivateTransparentModeHmm() {
	return field_trial::IsEnabled("WebRTC-Aec3TransparentModeHmmKillSwitch");
	}

	} // namespace

	// Classifier that toggles transparent mode which reduces echo suppression when
	// headsets are used.
	class TransparentModeImpl : public TransparentMode {
	public:
	bool Active() const override { return transparency_activated_; }

	void Reset() override {
	// Determines if transparent mode is used.
	transparency_activated_ = false;

	// The estimated probability of being transparent mode.
	prob_transparent_state_ = 0.f;
	}

	void Update(int filter_delay_blocks,
	bool any_filter_consistent,
	bool any_filter_converged,
	bool all_filters_diverged,
	bool active_render,
	bool saturated_capture) override {
	// The classifier is implemented as a Hidden Markov Model (HMM) with two
	// hidden states: "normal" and "transparent". The estimated probabilities of
	// the two states are updated by observing filter convergence during active
	// render. The filters are less likely to be reported as converged when
	// there is no echo present in the microphone signal.

	// The constants have been obtained by observing active_render and
	// any_filter_converged under varying call scenarios. They have further been
	// hand tuned to prefer normal state during uncertain regions (to avoid echo
	// leaks).

	// The model is only updated during active render.
	if (!active_render)
	return;

	// Probability of switching from one state to the other.
	constexpr float kSwitch = 0.000001f;

	// Probability of observing converged filters in states "normal" and
	// "transparent" during active render.
	constexpr float kConvergedNormal = 0.03f;
	constexpr float kConvergedTransparent = 0.005f;

	// Probability of transitioning to transparent state from normal state and
	// transparent state respectively.
	constexpr float kA[2] = {kSwitch, 1.f - kSwitch};

	// Probability of the two observations (converged filter or not converged
	// filter) in normal state and transparent state respectively.
	constexpr float kB[2][2] = {
	{1.f - kConvergedNormal, kConvergedNormal},
	{1.f - kConvergedTransparent, kConvergedTransparent}};

	// Probability of the two states before the update.
	const float prob_transparent = prob_transparent_state_;
	const float prob_normal = 1.f - prob_transparent;

	// Probability of transitioning to transparent state.
	const float prob_transition_transparent =
	prob_normal * kA[0] + prob_transparent * kA[1];
	const float prob_transition_normal = 1.f - prob_transition_transparent;

	// Observed output.
	const int out = any_filter_converged;

	// Joint probabilites of the observed output and respective states.
	const float prob_joint_normal = prob_transition_normal * kB[0][out];
	const float prob_joint_transparent =
	prob_transition_transparent * kB[1][out];

	// Conditional probability of transparent state and the observed output.
	RTC_DCHECK_GT(prob_joint_normal + prob_joint_transparent, 0.f);
	prob_transparent_state_ =
	prob_joint_transparent / (prob_joint_normal + prob_joint_transparent);

	// Transparent mode is only activated when its state probability is high.
	// Dead zone between activation/deactivation thresholds to avoid switching
	// back and forth.
	if (prob_transparent_state_ > 0.95f) {
	transparency_activated_ = true;
	} else if (prob_transparent_state_ < 0.5f) {
	transparency_activated_ = false;
	}
	}

	private:
	bool transparency_activated_ = false;
	float prob_transparent_state_ = 0.f;
	};

	// Legacy classifier for toggling transparent mode.
	class LegacyTransparentModeImpl : public TransparentMode {
	public:
	explicit LegacyTransparentModeImpl(const EchoCanceller3Config& config)
	: linear_and_stable_echo_path_(
	config.echo_removal_control.linear_and_stable_echo_path),
	active_blocks_since_sane_filter_(kBlocksSinceConsistentEstimateInit),
	non_converged_sequence_size_(kBlocksSinceConvergencedFilterInit) {}

	bool Active() const override { return transparency_activated_; }

	void Reset() override {
	non_converged_sequence_size_ = kBlocksSinceConvergencedFilterInit;
	diverged_sequence_size_ = 0;
	strong_not_saturated_render_blocks_ = 0;
	if (linear_and_stable_echo_path_) {
	recent_convergence_during_activity_ = false;
	}
	}

	void Update(int filter_delay_blocks,
	bool any_filter_consistent,
	bool any_filter_converged,
	bool all_filters_diverged,
	bool active_render,
	bool saturated_capture) override {
	++capture_block_counter_;
	strong_not_saturated_render_blocks_ +=
	active_render && !saturated_capture ? 1 : 0;

	if (any_filter_consistent && filter_delay_blocks < 5) {
	sane_filter_observed_ = true;
	active_blocks_since_sane_filter_ = 0;
	} else if (active_render) {
	++active_blocks_since_sane_filter_;
	}

	bool sane_filter_recently_seen;
	if (!sane_filter_observed_) {
	sane_filter_recently_seen =
	capture_block_counter_ <= 5 * kNumBlocksPerSecond;
	} else {
	sane_filter_recently_seen =
	active_blocks_since_sane_filter_ <= 30 * kNumBlocksPerSecond;
	}

	if (any_filter_converged) {
	recent_convergence_during_activity_ = true;
	active_non_converged_sequence_size_ = 0;
	non_converged_sequence_size_ = 0;
	++num_converged_blocks_;
	} else {
	if (++non_converged_sequence_size_ > 20 * kNumBlocksPerSecond) {
	num_converged_blocks_ = 0;
	}

	if (active_render &&
	++active_non_converged_sequence_size_ > 60 * kNumBlocksPerSecond) {
	recent_convergence_during_activity_ = false;
	}
	}

	if (!all_filters_diverged) {
	diverged_sequence_size_ = 0;
	} else if (++diverged_sequence_size_ >= 60) {
	// TODO(peah): Change these lines to ensure proper triggering of usable
	// filter.
	non_converged_sequence_size_ = kBlocksSinceConvergencedFilterInit;
	}

	if (active_non_converged_sequence_size_ > 60 * kNumBlocksPerSecond) {
	finite_erl_recently_detected_ = false;
	}
	if (num_converged_blocks_ > 50) {
	finite_erl_recently_detected_ = true;
	}

	if (finite_erl_recently_detected_) {
	transparency_activated_ = false;
	} else if (sane_filter_recently_seen &&
	recent_convergence_during_activity_) {
	transparency_activated_ = false;
	} else {
	const bool filter_should_have_converged =
	strong_not_saturated_render_blocks_ > 6 * kNumBlocksPerSecond;
	transparency_activated_ = filter_should_have_converged;
	}
	}

	private:
	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;
	};

	std::unique_ptr<TransparentMode> TransparentMode::Create(
	const EchoCanceller3Config& config) {
	if (config.ep_strength.bounded_erl \|\| DeactivateTransparentMode()) {
	return nullptr;
	}
	if (DeactivateTransparentModeHmm()) {
	return std::make_unique<LegacyTransparentModeImpl>(config);
	}
	return std::make_unique<TransparentModeImpl>();
	}

	} // namespace webrtc