Major updates to the echo removal functionality in AEC3

webrtc/modules/audio_processing/aec3/aec_state.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/aec_state.h"
 
 #include <math.h>
 #include <numeric>
 #include <vector>
 
+#include "webrtc/base/array_view.h"
 #include "webrtc/base/atomicops.h"
 #include "webrtc/base/checks.h"
 #include "webrtc/modules/audio_processing/logging/apm_data_dumper.h"
 
 namespace webrtc {
 namespace {
 
-constexpr float kMaxFilterEstimateStrength = 1000.f;
+constexpr size_t kEchoPathChangeConvergenceBlocks = 4 * kNumBlocksPerSecond;
+constexpr size_t kSaturationLeakageBlocks = 20;
 
-// Compute the delay of the adaptive filter as the partition with a distinct
-// peak.
-void AnalyzeFilter(
+// Computes delay of the adaptive filter.
+rtc::Optional<size_t> EstimateFilterDelay(
     const std::vector<std::array<float, kFftLengthBy2Plus1>>&
-        filter_frequency_response,
-    std::array<bool, kFftLengthBy2Plus1>* bands_with_reliable_filter,
-    std::array<float, kFftLengthBy2Plus1>* filter_estimate_strength,
-    rtc::Optional<size_t>* filter_delay) {
-  const auto& H2 = filter_frequency_response;
+        adaptive_filter_frequency_response) {
+  const auto& H2 = adaptive_filter_frequency_response;
 
   size_t reliable_delays_sum = 0;
   size_t num_reliable_delays = 0;
 
   constexpr size_t kUpperBin = kFftLengthBy2 - 5;
+  constexpr float kMinPeakMargin = 10.f;
+  const size_t kTailPartition = H2.size() - 1;
   for (size_t k = 1; k < kUpperBin; ++k) {
+    // Find the maximum of H2[j].
     int peak = 0;
     for (size_t j = 0; j < H2.size(); ++j) {
       if (H2[j][k] > H2[peak][k]) {
         peak = j;
       }
     }
 
-    if (H2[peak][k] == 0.f) {
-      (*filter_estimate_strength)[k] = 0.f;
-    } else if (H2[H2.size() - 1][k] == 0.f) {
-      (*filter_estimate_strength)[k] = kMaxFilterEstimateStrength;
-    } else {
-      (*filter_estimate_strength)[k] = std::min(
-          kMaxFilterEstimateStrength, H2[peak][k] / H2[H2.size() - 1][k]);
-    }
-
-    constexpr float kMargin = 10.f;
-    if (kMargin * H2[H2.size() - 1][k] < H2[peak][k]) {
-      (*bands_with_reliable_filter)[k] = true;
+    // Count the peak as a delay only if the peak is sufficiently larger than
+    // the tail.
+    if (kMinPeakMargin * H2[kTailPartition][k] < H2[peak][k]) {
       reliable_delays_sum += peak;
       ++num_reliable_delays;
-    } else {
-      (*bands_with_reliable_filter)[k] = false;
     }
   }
-  (*bands_with_reliable_filter)[0] = (*bands_with_reliable_filter)[1];
-  std::fill(bands_with_reliable_filter->begin() + kUpperBin,
-            bands_with_reliable_filter->end(),
-            (*bands_with_reliable_filter)[kUpperBin - 1]);
-  (*filter_estimate_strength)[0] = (*filter_estimate_strength)[1];
-  std::fill(filter_estimate_strength->begin() + kUpperBin,
-            filter_estimate_strength->end(),
-            (*filter_estimate_strength)[kUpperBin - 1]);
 
-  *filter_delay =
-      num_reliable_delays > 20
-          ? rtc::Optional<size_t>(reliable_delays_sum / num_reliable_delays)
-          : rtc::Optional<size_t>();
+  // Return no delay if not sufficient delays have been found.
+  if (num_reliable_delays < 21) {
+    return rtc::Optional<size_t>();
+  }
+
+  const size_t delay = reliable_delays_sum / num_reliable_delays;
+  // Sanity check that the peak is not caused by a false strong DC-component in
+  // the filter.
+  for (size_t k = 1; k < kUpperBin; ++k) {
+    if (H2[delay][k] > H2[delay][0]) {
+      RTC_DCHECK_GT(H2.size(), delay);
+      return rtc::Optional<size_t>(delay);
+    }
+  }
+  return rtc::Optional<size_t>();
 }
 
-constexpr int kActiveRenderCounterInitial = 50;
-constexpr int kActiveRenderCounterMax = 200;
-constexpr int kEchoPathChangeCounterInitial = 50;
-constexpr int kEchoPathChangeCounterMax = 3 * 250;
+constexpr int kEchoPathChangeCounterInitial = kNumBlocksPerSecond / 5;
+constexpr int kEchoPathChangeCounterMax = 3 * kNumBlocksPerSecond;
 
 }  // namespace
 
 int AecState::instance_count_ = 0;
 
 AecState::AecState()
     : data_dumper_(
           new ApmDataDumper(rtc::AtomicOps::Increment(&instance_count_))),
-      echo_path_change_counter_(kEchoPathChangeCounterInitial),
-      active_render_counter_(kActiveRenderCounterInitial) {
-  bands_with_reliable_filter_.fill(false);
-  filter_estimate_strength_.fill(0.f);
-}
+      echo_path_change_counter_(kEchoPathChangeCounterInitial) {}
 
 AecState::~AecState() = default;
 
+void AecState::HandleEchoPathChange(
+    const EchoPathVariability& echo_path_variability) {
+  if (echo_path_variability.AudioPathChanged()) {
+    blocks_since_last_saturation_ = 0;
+    active_render_blocks_ = 0;
+    echo_path_change_counter_ = kEchoPathChangeCounterMax;
+    usable_linear_estimate_ = false;
+    echo_leakage_detected_ = false;
+    capture_signal_saturation_ = false;
+    echo_saturation_ = false;
+    headset_detected_ = false;
+    previous_max_sample_ = 0.f;
+  }
+}
+
 void AecState::Update(const std::vector<std::array<float, kFftLengthBy2Plus1>>&
-                          filter_frequency_response,
+                          adaptive_filter_frequency_response,
                       const rtc::Optional<size_t>& external_delay_samples,
-                      const RenderBuffer& X_buffer,
+                      const RenderBuffer& render_buffer,
                       const std::array<float, kFftLengthBy2Plus1>& E2_main,
-                      const std::array<float, kFftLengthBy2Plus1>& E2_shadow,
                       const std::array<float, kFftLengthBy2Plus1>& Y2,
                       rtc::ArrayView<const float> x,
-                      const EchoPathVariability& echo_path_variability,
                       bool echo_leakage_detected) {
-  filter_length_ = filter_frequency_response.size();
-  AnalyzeFilter(filter_frequency_response, &bands_with_reliable_filter_,
-                &filter_estimate_strength_, &filter_delay_);
-  // Compute the externally provided delay in partitions. The truncation is
-  // intended here.
+  // Store input parameters.
+  echo_leakage_detected_ = echo_leakage_detected;
+
+  // Update counters.
+  const float x_energy = std::inner_product(x.begin(), x.end(), x.begin(), 0.f);
+  const bool active_render_block = x_energy > 10000.f * kFftLengthBy2;
+  active_render_blocks_ += active_render_block ? 1 : 0;
+  --echo_path_change_counter_;
+
+  // Estimate delays.
+  filter_delay_ = EstimateFilterDelay(adaptive_filter_frequency_response);
   external_delay_ =
       external_delay_samples
           ? rtc::Optional<size_t>(*external_delay_samples / kBlockSize)
           : rtc::Optional<size_t>();
 
-  const float x_energy = std::inner_product(x.begin(), x.end(), x.begin(), 0.f);
-
-  active_render_blocks_ =
-      echo_path_variability.AudioPathChanged() ? 0 : active_render_blocks_ + 1;
-
-  echo_path_change_counter_ = echo_path_variability.AudioPathChanged()
-                                  ? kEchoPathChangeCounterMax
-                                  : echo_path_change_counter_ - 1;
-  active_render_counter_ = x_energy > 10000.f * kFftLengthBy2
-                               ? kActiveRenderCounterMax
-                               : active_render_counter_ - 1;
-
-  usable_linear_estimate_ = filter_delay_ && echo_path_change_counter_ <= 0;
-
-  echo_leakage_detected_ = echo_leakage_detected;
-
-  model_based_aec_feasible_ = usable_linear_estimate_ || external_delay_;
-
-  if (usable_linear_estimate_) {
-    const auto& X2 = X_buffer.Spectrum(*filter_delay_);
-
-    // TODO(peah): Expose these as stats.
+  // Update the ERL and ERLE measures.
+  if (filter_delay_ && echo_path_change_counter_ <= 0) {
+    const auto& X2 = render_buffer.Spectrum(*filter_delay_);
     erle_estimator_.Update(X2, Y2, E2_main);
     erl_estimator_.Update(X2, Y2);
+  }
 
-// TODO(peah): Add working functionality for headset detection. Until the
-// functionality for that is working the headset detector is hardcoded to detect
-// no headset.
-#if 0
-    const auto& erl = erl_estimator_.Erl();
-    const int low_erl_band_count = std::count_if(
-        erl.begin(), erl.end(), [](float a) { return a <= 0.1f; });
+  // Detect and flag echo saturation.
+  RTC_DCHECK_LT(0, x.size());
+  const float max_sample = fabs(*std::max_element(
+      x.begin(), x.end(), [](float a, float b) { return a * a < b * b; }));
+  const bool saturated_echo =
+      previous_max_sample_ * kFixedEchoPathGain > 1600 && SaturatedCapture();
+  previous_max_sample_ = max_sample;
 
-    const int noisy_band_count = std::count_if(
-        filter_estimate_strength_.begin(), filter_estimate_strength_.end(),
-        [](float a) { return a <= 10.f; });
-    headset_detected_ = low_erl_band_count > 20 && noisy_band_count > 20;
-#endif
-    headset_detected_ = false;
-  } else {
-    headset_detected_ = false;
-  }
+  // Counts the blocks since saturation.
+  blocks_since_last_saturation_ =
+      saturated_echo ? 0 : blocks_since_last_saturation_ + 1;
+  echo_saturation_ = blocks_since_last_saturation_ < kSaturationLeakageBlocks;
+
+  // Flag whether the linear filter estimate is usable.
+  usable_linear_estimate_ =
+      (!echo_saturation_) &&
+      active_render_blocks_ > kEchoPathChangeConvergenceBlocks &&
+      filter_delay_ && echo_path_change_counter_ <= 0;
+
+  // 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, flag that a
+  // headset is used.
+  headset_detected_ = !external_delay_ && !filter_delay_ &&
+                      active_render_blocks_ >= kEchoPathChangeConvergenceBlocks;
 }
 
 }  // namespace webrtc