Added post-adjustment of the suppression gains

webrtc/modules/audio_processing/aec3/suppression_filter.cc

Index: webrtc/modules/audio_processing/aec3/suppression_filter.cc
diff --git a/webrtc/modules/audio_processing/aec3/suppression_filter.cc b/webrtc/modules/audio_processing/aec3/suppression_filter.cc
index 358aafbdfb3777f0a5cb8fe05076d9cd0a4dc1ee..30e99a6279b7c1c5b4bc070e1828b9e76425ed3b 100644
--- a/webrtc/modules/audio_processing/aec3/suppression_filter.cc
+++ b/webrtc/modules/audio_processing/aec3/suppression_filter.cc
@@ -138,17 +138,14 @@ void SuppressionFilter::ApplyGain(
     fft_.Ifft(E, &time_domain_high_band_noise);
 
     // Scale and apply the noise to the signals.
-    // TODO(peah): Ensure that the high bands are properly delayed.
-    constexpr int kNumBandsAveragingUpperGain = kFftLengthBy2 / 4;
-    constexpr float kOneByNumBandsAveragingUpperGain =
-        1.f / kNumBandsAveragingUpperGain;
-    float high_bands_gain =
-        std::accumulate(suppression_gain.end() - kNumBandsAveragingUpperGain,
-                        suppression_gain.end(), 0.f) *
-        kOneByNumBandsAveragingUpperGain;
+    constexpr int kLowestAnalysisBin = 3;
+    float high_bands_gain = std::accumulate(

[hlundin-webrtc, 2017/02/27 08:12:52]

Iiuc, this is not an accumulation at all. You are picking out the minimum
element in the range, right? If so, why not just use std::min_element?

[peah-webrtc, 2017/02/27 08:25:47]

Great suggestion! Thanks!

Done.

+        suppression_gain.begin() + kLowestAnalysisBin + 1,
+        suppression_gain.end(), suppression_gain[kLowestAnalysisBin],
+        [](float a, float b) { return std::min(a, b); });
 
     float high_bands_noise_scaling =
-        0.4f * std::max(1.f - high_bands_gain * high_bands_gain, 0.f);
+        0.4f * std::max(1.f - high_bands_gain, 0.f);

[peah-webrtc, 2017/02/27 07:55:22]

The former computation of high_bands_noise_scaling is a leftover from AEC2.
There is no reason why the square should be there, so I removed it as that may
cause the comfort noise to be too high.

[hlundin-webrtc, 2017/02/27 08:12:51]

Acknowledged.

 
     std::transform(
         (*e)[1].begin(), (*e)[1].end(), time_domain_high_band_noise.begin(),