Finalization of the first version of EchoCanceller 3

webrtc/modules/audio_processing/aec3/residual_echo_estimator.cc

+/*
+ *  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 "webrtc/modules/audio_processing/aec3/residual_echo_estimator.h"
+
+#include <math.h>
+#include <vector>
+
+#include "webrtc/base/checks.h"
+
+namespace webrtc {
+namespace {
+
+constexpr float kSaturationLeakageFactor = 10.f;
+constexpr size_t kSaturationLeakageBlocks = 10;
+
+// Estimates the residual echo power when there is no detection correlation
+// between the render and capture signals.
+void InfiniteErlPowerEstimate(
+    size_t active_render_counter,
+    size_t blocks_since_last_saturation,
+    const std::array<float, kFftLengthBy2Plus1>& S2_fallback,
+    std::array<float, kFftLengthBy2Plus1>* R2) {
+  if (active_render_counter > 5 * 250) {
+    // After an amount of active render samples for which an echo should have
+    // been detected in the capture signal if the ERL was not infinite, set the
+    // residual echo to 0.
+    R2->fill(0.f);
+  } else {
+    // Before certainty has been reached about the presence of echo, use the
+    // fallback echo power estimate as the residual echo estimate. Add a leakage
+    // factor when there is saturation.
+    std::copy(S2_fallback.begin(), S2_fallback.end(), R2->begin());
+    if (blocks_since_last_saturation < kSaturationLeakageBlocks) {
+      std::for_each(R2->begin(), R2->end(),
+                    [](float& a) { a *= kSaturationLeakageFactor; });
+    }
+  }
+}
+
+// Estimates the echo power in an half-duplex manner.
+void HalfDuplexPowerEstimate(bool active_render,
+                             const std::array<float, kFftLengthBy2Plus1>& Y2,
+                             std::array<float, kFftLengthBy2Plus1>* R2) {
+  // Set the residual echo power to the power of the capture signal.
+  if (active_render) {
+    std::copy(Y2.begin(), Y2.end(), R2->begin());
+  } else {
+    R2->fill(0.f);
+  }
+}
+
+// Estimates the residual echo power based on gains.
+void GainBasedPowerEstimate(
+    size_t external_delay,
+    const FftBuffer& X_buffer,
+    size_t blocks_since_last_saturation,
+    const std::array<bool, kFftLengthBy2Plus1>& bands_with_reliable_filter,
+    const std::array<float, kFftLengthBy2Plus1>& echo_path_gain,
+    const std::array<float, kFftLengthBy2Plus1>& S2_fallback,
+    std::array<float, kFftLengthBy2Plus1>* R2) {
+  const auto& X2 = X_buffer.Spectrum(external_delay);
+
+  // Base the residual echo power on gain of the linear echo path estimate if
+  // that is reliable, otherwise use the fallback echo path estimate. Add a
+  // leakage factor when there is saturation.
+  for (size_t k = 0; k < R2->size(); ++k) {
+    (*R2)[k] = bands_with_reliable_filter[k] ? echo_path_gain[k] * X2[k]
+                                             : S2_fallback[k];
+  }
+  if (blocks_since_last_saturation < kSaturationLeakageBlocks) {
+    std::for_each(R2->begin(), R2->end(),
+                  [](float& a) { a *= kSaturationLeakageFactor; });
+  }
+}
+
+// Estimates the residual echo power based on the linear echo path.
+void ErleBasedPowerEstimate(
+    bool headset_detected,
+    const FftBuffer& X_buffer,
+    bool using_subtractor_output,
+    size_t linear_filter_based_delay,
+    size_t blocks_since_last_saturation,
+    bool poorly_aligned_filter,
+    const std::array<bool, kFftLengthBy2Plus1>& bands_with_reliable_filter,
+    const std::array<float, kFftLengthBy2Plus1>& echo_path_gain,
+    const std::array<float, kFftLengthBy2Plus1>& S2_fallback,
+    const std::array<float, kFftLengthBy2Plus1>& S2_linear,
+    const std::array<float, kFftLengthBy2Plus1>& Y2,
+    const std::array<float, kFftLengthBy2Plus1>& erle,
+    const std::array<float, kFftLengthBy2Plus1>& erl,
+    std::array<float, kFftLengthBy2Plus1>* R2) {
+  // Residual echo power after saturation.
+  if (blocks_since_last_saturation < kSaturationLeakageBlocks) {
+    for (size_t k = 0; k < R2->size(); ++k) {
+      (*R2)[k] = kSaturationLeakageFactor *
+                 (bands_with_reliable_filter[k] && using_subtractor_output
+                      ? S2_linear[k]
+                      : std::min(S2_fallback[k], Y2[k]));
+    }
+    return;
+  }
+
+  // Residual echo power when a headset is used.
+  if (headset_detected) {
+    const auto& X2 = X_buffer.Spectrum(linear_filter_based_delay);
+    for (size_t k = 0; k < R2->size(); ++k) {
+      RTC_DCHECK_LT(0.f, erle[k]);
+      (*R2)[k] = bands_with_reliable_filter[k] && using_subtractor_output
+                     ? S2_linear[k] / erle[k]
+                     : std::min(S2_fallback[k], Y2[k]);
+      (*R2)[k] = std::min((*R2)[k], X2[k] * erl[k]);
+    }
+    return;
+  }
+
+  // Residual echo power when the adaptive filter is poorly aligned.
+  if (poorly_aligned_filter) {
+    for (size_t k = 0; k < R2->size(); ++k) {
+      (*R2)[k] = bands_with_reliable_filter[k] && using_subtractor_output
+                     ? S2_linear[k]
+                     : std::min(S2_fallback[k], Y2[k]);
+    }
+    return;
+  }
+
+  // Residual echo power when there is no recent saturation, no headset detected
+  // and when the adaptive filter is well aligned.
+  for (size_t k = 0; k < R2->size(); ++k) {
+    RTC_DCHECK_LT(0.f, erle[k]);
+    const auto& X2 = X_buffer.Spectrum(linear_filter_based_delay);
+    (*R2)[k] = bands_with_reliable_filter[k] && using_subtractor_output
+                   ? S2_linear[k] / erle[k]
+                   : std::min(echo_path_gain[k] * X2[k], Y2[k]);
+  }
+}
+
+}  // namespace
+
+ResidualEchoEstimator::ResidualEchoEstimator() {
+  echo_path_gain_.fill(0.f);
+}
+
+ResidualEchoEstimator::~ResidualEchoEstimator() = default;
+
+void ResidualEchoEstimator::Estimate(
+    bool using_subtractor_output,
+    const AecState& aec_state,
+    const FftBuffer& X_buffer,
+    const std::vector<std::array<float, kFftLengthBy2Plus1>>& H2,
+    const std::array<float, kFftLengthBy2Plus1>& E2_main,
+    const std::array<float, kFftLengthBy2Plus1>& E2_shadow,
+    const std::array<float, kFftLengthBy2Plus1>& S2_linear,
+    const std::array<float, kFftLengthBy2Plus1>& S2_fallback,
+    const std::array<float, kFftLengthBy2Plus1>& Y2,
+    std::array<float, kFftLengthBy2Plus1>* R2) {
+  RTC_DCHECK(R2);
+  const rtc::Optional<size_t>& linear_filter_based_delay =
+      aec_state.FilterDelay();
+
+  // Update the echo path gain.
+  if (linear_filter_based_delay) {
+    std::copy(H2[*linear_filter_based_delay].begin(),
+              H2[*linear_filter_based_delay].end(), echo_path_gain_.begin());
+  }
+
+  // Counts the blocks since saturation.
+  if (aec_state.SaturatedCapture()) {
+    blocks_since_last_saturation_ = 0;
+  } else {
+    ++blocks_since_last_saturation_;
+  }
+
+  // Counts the number of active render blocks that are in a row.
+  if (aec_state.ActiveRender()) {
+    ++active_render_counter_;
+  }
+
+  const auto& bands_with_reliable_filter = aec_state.BandsWithReliableFilter();
+
+  if (aec_state.UsableLinearEstimate()) {
+    // Residual echo power estimation when the adaptive filter is reliable.
+    RTC_DCHECK(linear_filter_based_delay);
+    ErleBasedPowerEstimate(
+        aec_state.HeadsetDetected(), X_buffer, using_subtractor_output,
+        *linear_filter_based_delay, blocks_since_last_saturation_,
+        aec_state.PoorlyAlignedFilter(), bands_with_reliable_filter,
+        echo_path_gain_, S2_fallback, S2_linear, Y2, aec_state.Erle(),
+        aec_state.Erl(), R2);
+  } else if (aec_state.ModelBasedAecFeasible()) {
+    // Residual echo power when the adaptive filter is not reliable but still an
+    // external echo path delay is provided (and hence can be estimated).
+    RTC_DCHECK(aec_state.ExternalDelay());
+    GainBasedPowerEstimate(
+        *aec_state.ExternalDelay(), X_buffer, blocks_since_last_saturation_,
+        bands_with_reliable_filter, echo_path_gain_, S2_fallback, R2);
+  } else if (aec_state.EchoLeakageDetected()) {
+    // Residual echo power when an external residual echo detection algorithm
+    // has deemed the echo canceller to leak echoes.
+    HalfDuplexPowerEstimate(aec_state.ActiveRender(), Y2, R2);
+  } else {
+    // Residual echo power when none of the other cases are fulfilled.
+    InfiniteErlPowerEstimate(active_render_counter_,
+                             blocks_since_last_saturation_, S2_fallback, R2);
+  }
+}
+
+}  // namespace webrtc