Add adaptive notch filter to remove narrowband echo components in AEC3

webrtc/modules/audio_processing/aec3/suppression_gain.cc

Index: webrtc/modules/audio_processing/aec3/suppression_gain.cc
diff --git a/webrtc/modules/audio_processing/aec3/suppression_gain.cc b/webrtc/modules/audio_processing/aec3/suppression_gain.cc
index c8465eaff679807de445ad3e6c64862946be82a1..02ca3dcd888cc56afff14b216eeba910721eb180 100644
--- a/webrtc/modules/audio_processing/aec3/suppression_gain.cc
+++ b/webrtc/modules/audio_processing/aec3/suppression_gain.cc
@@ -25,6 +25,16 @@
 namespace webrtc {
 namespace {
 
+// Reduce gain to avoid narrow band echo leakage.
+void NarrowBandAttenuation(int narrow_bin,
+                           std::array<float, kFftLengthBy2Plus1>* gain) {
+  const int upper_bin =
+      std::min(narrow_bin + 6, static_cast<int>(kFftLengthBy2Plus1 - 1));
+  for (int k = std::max(0, narrow_bin - 6); k <= upper_bin; ++k) {
+    (*gain)[k] = std::min((*gain)[k], 0.001f);
+  }
+}
+
 // Adjust the gains according to the presence of known external filters.
 void AdjustForExternalFilters(std::array<float, kFftLengthBy2Plus1>* gain) {
   // Limit the low frequency gains to avoid the impact of the high-pass filter
@@ -45,6 +55,7 @@ void AdjustForExternalFilters(std::array<float, kFftLengthBy2Plus1>* gain) {
 
 // Computes the gain to apply for the bands beyond the first band.
 float UpperBandsGain(
+    const RenderSignalAnalyzer& render_signal_analyzer,
     bool saturated_echo,
     const std::vector<std::vector<float>>& render,
     const std::array<float, kFftLengthBy2Plus1>& low_band_gain) {
@@ -53,6 +64,12 @@ float UpperBandsGain(
     return 1.f;
   }
 
+  if (render_signal_analyzer.NarrowPeakBand() &&

[ivoc, 2017/07/11 11:06:50]

I think it makes sense to store this in a temporary variable.

[peah-webrtc, 2017/07/11 11:54:18]

I changed it to a separate input argument. Unfortunately, the double check of
the optional cannot be avoided though.

Done.

+      (*render_signal_analyzer.NarrowPeakBand() >
+       static_cast<int>(kFftLengthBy2Plus1 - 10))) {
+    return 0.001f;
+  }
+
   constexpr size_t kLowBandGainLimit = kFftLengthBy2 / 2;
   const float gain_below_8_khz = *std::min_element(
       low_band_gain.begin() + kLowBandGainLimit, low_band_gain.end());
@@ -193,6 +210,7 @@ void MaskingPower(const std::array<float, kFftLengthBy2Plus1>& nearend,
 // TODO(peah): Add further optimizations, in particular for the divisions.
 void SuppressionGain::LowerBandGain(
     bool low_noise_render,
+    const RenderSignalAnalyzer& render_signal_analyzer,
     bool saturated_echo,
     const std::array<float, kFftLengthBy2Plus1>& nearend,
     const std::array<float, kFftLengthBy2Plus1>& echo,
@@ -238,6 +256,9 @@ void SuppressionGain::LowerBandGain(
     GainToNoAudibleEcho(low_noise_render, saturated_echo, nearend, echo, masker,
                         min_gain, max_gain, one_by_echo, gain);
     AdjustForExternalFilters(gain);
+    if (render_signal_analyzer.NarrowPeakBand()) {
+      NarrowBandAttenuation(*render_signal_analyzer.NarrowPeakBand(), gain);
+    }
   }
 
   // Update the allowed maximum gain increase.
@@ -263,6 +284,7 @@ void SuppressionGain::GetGain(
     const std::array<float, kFftLengthBy2Plus1>& nearend,
     const std::array<float, kFftLengthBy2Plus1>& echo,
     const std::array<float, kFftLengthBy2Plus1>& comfort_noise,
+    const RenderSignalAnalyzer& render_signal_analyzer,

[ivoc, 2017/07/11 11:06:50]

This object is passed around a lot, but it seems like only
render_signal_analyzer.NarrowPeakBand() is actually used. I think it makes sense
to pass this directly as a bool instead (here and in the other functions), wdyt?

[peah-webrtc, 2017/07/11 11:54:18]

Good point! I changed the code along that, but as it return an
rtc::Optional<int> I needed to pass that around. But regardless of that, with
this suggestion the code becomes much better.

Done.

     bool saturated_echo,
     const std::vector<std::vector<float>>& render,
     bool force_zero_gain,
@@ -283,11 +305,12 @@ void SuppressionGain::GetGain(
   bool low_noise_render = low_render_detector_.Detect(render);
 
   // Compute gain for the lower band.
-  LowerBandGain(low_noise_render, saturated_echo, nearend, echo, comfort_noise,
-                low_band_gain);
+  LowerBandGain(low_noise_render, render_signal_analyzer, saturated_echo,
+                nearend, echo, comfort_noise, low_band_gain);
 
   // Compute the gain for the upper bands.
-  *high_bands_gain = UpperBandsGain(saturated_echo, render, *low_band_gain);
+  *high_bands_gain = UpperBandsGain(render_signal_analyzer, saturated_echo,
+                                    render, *low_band_gain);
 }
 
 // Detects when the render signal can be considered to have low power and