Adding support for handling highly reverberant echoes in AEC3

webrtc/modules/audio_processing/aec3/residual_echo_estimator.h

Index: webrtc/modules/audio_processing/aec3/residual_echo_estimator.h
diff --git a/webrtc/modules/audio_processing/aec3/residual_echo_estimator.h b/webrtc/modules/audio_processing/aec3/residual_echo_estimator.h
index 1334e63256b475b3a7bd024fe86fec792e1ff50b..d53612d430cb50324ece69fe2912a74e777936dd 100644
--- a/webrtc/modules/audio_processing/aec3/residual_echo_estimator.h
+++ b/webrtc/modules/audio_processing/aec3/residual_echo_estimator.h
@@ -36,8 +36,37 @@ class ResidualEchoEstimator {
                 std::array<float, kFftLengthBy2Plus1>* R2);
 
  private:
+  // Resets the state.
+  void Reset();
+
+  // Estimates the residual echo power based on the erle and the linear power

[AleBzk, 2017/04/07 09:34:39]

"erle" stands for Echo Return Loss Enhancement, right? Since it's the first time
you use the acronym in this file, I would write the full name and then "(erle)"
- it also helps to understand the role of the variable in the LinearEstimate
signature. As an AEC newbie, that would help me to better follow the signal
processing pipeline. However, if you think it should be obvious, just ignore
this comment.

[peah-webrtc, 2017/04/07 12:19:44]

Good point! Will do that!
Done.

+  // estimate.
+  void LinearEstimate(const std::array<float, kFftLengthBy2Plus1>& S2_linear,
+                      const std::array<float, kFftLengthBy2Plus1>& erle,
+                      size_t delay,
+                      std::array<float, kFftLengthBy2Plus1>* R2);
+
+  // Estimates the residual echo power based on the estimate of the echo path
+  // gain.
+  void NonLinearEstimate(const std::array<float, kFftLengthBy2Plus1>& X2,
+                         const std::array<float, kFftLengthBy2Plus1>& Y2,
+                         std::array<float, kFftLengthBy2Plus1>* R2);
+
+  // Adds the estimated unmodelled echo power to the residual echo power
+  // estimate.
+  void AddEchoReverb(const std::array<float, kFftLengthBy2Plus1>& S2,
+                     bool saturated_echo,
+                     size_t delay,
+                     float reverb_decay_factor,
+                     std::array<float, kFftLengthBy2Plus1>* R2);
+
   std::array<float, kFftLengthBy2Plus1> R2_old_;
   std::array<int, kFftLengthBy2Plus1> R2_hold_counter_;
+  std::array<float, kFftLengthBy2Plus1> R2_reverb_;
+  int S2_old_index_ = 0;
+  std::array<std::array<float, kFftLengthBy2Plus1>, kAdaptiveFilterLength>
+      S2_old_;
+  bool headset_detected_cached_ = false;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(ResidualEchoEstimator);
 };