Improved low-level echo handling in echo canceller 3

webrtc/modules/audio_processing/aec3/suppression_gain.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 140 matching lines @@
     bool saturated_echo,
     const std::array<float, kFftLengthBy2Plus1>& nearend,
     const std::array<float, kFftLengthBy2Plus1>& echo,
     const std::array<float, kFftLengthBy2Plus1>& masker,
     const std::array<float, kFftLengthBy2Plus1>& min_gain,
     const std::array<float, kFftLengthBy2Plus1>& max_gain,
     const std::array<float, kFftLengthBy2Plus1>& one_by_echo,
     std::array<float, kFftLengthBy2Plus1>* gain) {
   constexpr float kEchoMaskingMargin = 1.f / 100.f;
   const float nearend_masking_margin =
-      low_noise_render ? 2.f : (saturated_echo ? 0.001f : 0.01f);
+      low_noise_render ? 0.1f : (saturated_echo ? 0.001f : 0.01f);
 
   for (size_t k = 0; k < gain->size(); ++k) {
     RTC_DCHECK_LE(0.f, nearend_masking_margin * nearend[k]);
     if (echo[k] <= nearend_masking_margin * nearend[k]) {
       (*gain)[k] = 1.f;
     } else {
       (*gain)[k] = kEchoMaskingMargin * masker[k] * one_by_echo[k];
     }
 
     (*gain)[k] = std::min(std::max((*gain)[k], min_gain[k]), max_gain[k]);
@@ skipping 131 matching lines @@
   }
 
   constexpr float kThreshold = 50.f * 50.f * 64.f;
   const bool low_noise_render =
       average_power_ < kThreshold && x2_max < 3 * average_power_;
   average_power_ = average_power_ * 0.9f + x2_sum * 0.1f;
   return low_noise_render;
 }
 
 }  // namespace webrtc