Robustify the AEC3 inaudible echo detection

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.
  */
 
@@ skipping 126 matching lines @@
         [](float a, float b) { return std::max(0.f, a - 10.f * b); });
 
     NonLinearEstimate(aec_state.HeadsetDetected(), X2, Y2, R2);
     AddEchoReverb(*R2, aec_state.SaturatedEcho(),
                   std::min(static_cast<size_t>(kAdaptiveFilterLength),
                            delay.value_or(kAdaptiveFilterLength)),
                   aec_state.ReverbDecay(), R2);
   }
 
   // If the echo is deemed inaudible, set the residual echo to zero.
-  if (aec_state.InaudibleEcho()) {
+  if (aec_state.InaudibleEcho() &&
+      (aec_state.ExternalDelay() || aec_state.HeadsetDetected())) {
     R2->fill(0.f);
   }
 
   // If the echo is saturated, estimate the echo power as the maximum echo power
   // with a leakage factor.
   if (aec_state.SaturatedEcho()) {
     R2->fill((*std::max_element(R2->begin(), R2->end())) * 100.f);
   }
 
   std::copy(R2->begin(), R2->end(), R2_old_.begin());
@@ skipping 93 matching lines @@
   } else {
     std::copy(S2.begin(), S2.end(), S2_old_[S2_old_index_].begin());
   }
 
   // Add the power of the echo reverb to the residual echo power.
   std::transform(R2->begin(), R2->end(), R2_reverb_.begin(), R2->begin(),
                  std::plus<float>());
 }
 
 }  // namespace webrtc