Added forced zero AEC output after call startup and echo path changes

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.
  */
 
@@ skipping 79 matching lines @@
   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;
+
+    if (echo_path_variability.delay_change) {
+      force_zero_gain_counter_ = 0;
+      force_zero_gain_ = true;
+    }
   }
 }
 
 void AecState::Update(const std::vector<std::array<float, kFftLengthBy2Plus1>>&
                           adaptive_filter_frequency_response,
                       const rtc::Optional<size_t>& external_delay_samples,
                       const RenderBuffer& render_buffer,
                       const std::array<float, kFftLengthBy2Plus1>& E2_main,
                       const std::array<float, kFftLengthBy2Plus1>& Y2,
                       rtc::ArrayView<const float> x,
                       bool echo_leakage_detected) {
   // 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_;
 
+  // Force zero echo suppression gain after an echo path change to allow at
+  // least some render data to be collected in order to avoid an initial echo
+  // burst.
+  constexpr size_t kZeroGainBlocksAfterChange = kNumBlocksPerSecond / 5;
+  force_zero_gain_ = (++force_zero_gain_counter_) < kZeroGainBlocksAfterChange;
+
   // 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>();
 
   // Update the ERL and ERLE measures.
   if (filter_delay_ && echo_path_change_counter_ <= 0) {
     const auto& X2 = render_buffer.Spectrum(*filter_delay_);
@@ skipping 21 matching lines @@
       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