Make AEC3 recover more quickly for lost capture data

webrtc/modules/audio_processing/aec3/block_processor.cc

 /*
  *  Copyright (c) 2016 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/block_processor.h"
@@ skipping 94 matching lines @@
 
   // Update the render buffers with new render data, filling the buffers with
   // empty blocks when there is no render data available.
   render_buffer_underrun = !render_buffer_->UpdateBuffers();
 
   // Compute and and apply the render delay required to achieve proper signal
   // alignment.
   const size_t old_delay = render_buffer_->Delay();
   const size_t new_delay = delay_controller_->GetDelay(
       render_buffer_->GetDownsampledRenderBuffer(), (*capture_block)[0]);
-  render_buffer_->SetDelay(new_delay);
-  const size_t achieved_delay = render_buffer_->Delay();
 
-  // Inform the delay controller of the actually set delay to allow it to
-  // properly react to a non-feasible delay.
-  delay_controller_->SetDelay(achieved_delay);
+  bool delay_change;
+  if (new_delay >= kMinEchoPathDelayBlocks) {
+    render_buffer_->SetDelay(new_delay);
+    const size_t achieved_delay = render_buffer_->Delay();
+    delay_change = old_delay != achieved_delay || old_delay != new_delay ||
+                   render_buffer_overrun_occurred_;
+
+    // Inform the delay controller of the actually set delay to allow it to
+    // properly react to a non-feasible delay.
+    delay_controller_->SetDelay(achieved_delay);
+  } else {
+    delay_controller_->Reset();
+    render_buffer_->Reset();
+    delay_change = true;
+  }
 
   // Remove the echo from the capture signal.
   echo_remover_->ProcessCapture(
       delay_controller_->AlignmentHeadroomSamples(),
-      EchoPathVariability(echo_path_gain_change,
-                          old_delay != achieved_delay ||
-                              old_delay != new_delay ||
-                              render_buffer_overrun_occurred_),
+      EchoPathVariability(echo_path_gain_change, delay_change),
       capture_signal_saturation, render_buffer_->GetRenderBuffer(),
       capture_block);
 
   // Update the metrics.
   metrics_.UpdateCapture(render_buffer_underrun);
 
   render_buffer_overrun_occurred_ = false;
 }
 
 void BlockProcessorImpl::BufferRender(
@@ skipping 59 matching lines @@
     int sample_rate_hz,
     std::unique_ptr<RenderDelayBuffer> render_buffer,
     std::unique_ptr<RenderDelayController> delay_controller,
     std::unique_ptr<EchoRemover> echo_remover) {
   return new BlockProcessorImpl(sample_rate_hz, std::move(render_buffer),
                                 std::move(delay_controller),
                                 std::move(echo_remover));
 }
 
 }  // namespace webrtc