Make the high frequency correction range depend on the target angle

webrtc/modules/audio_processing/beamformer/nonlinear_beamformer.cc

Index: webrtc/modules/audio_processing/beamformer/nonlinear_beamformer.cc
diff --git a/webrtc/modules/audio_processing/beamformer/nonlinear_beamformer.cc b/webrtc/modules/audio_processing/beamformer/nonlinear_beamformer.cc
index fec93778d872a6c4b53a0f98de45d0b3095f42d5..0f76dbf0c620bc97b88a878125c8f4b45083eb3e 100644
--- a/webrtc/modules/audio_processing/beamformer/nonlinear_beamformer.cc
+++ b/webrtc/modules/audio_processing/beamformer/nonlinear_beamformer.cc
@@ -61,11 +61,6 @@ const float kMaskFrequencySmoothAlpha = 0.6f;
 const int kLowMeanStartHz = 200;
 const int kLowMeanEndHz = 400;
 
-// TODO(aluebs): Make the high frequency correction range depend on the target
-// angle.
-const int kHighMeanStartHz = 3000;
-const int kHighMeanEndHz = 5000;
-
 // Range limiter for subtractive terms in the nominator and denominator of the
 // postfilter expression. It handles the scenario mismatch between the true and
 // model sources (target and interference).
@@ -221,25 +216,7 @@ void NonlinearBeamformer::Initialize(int chunk_size_ms, int sample_rate_hz) {
   chunk_length_ =
       static_cast<size_t>(sample_rate_hz / (1000.f / chunk_size_ms));
   sample_rate_hz_ = sample_rate_hz;
-  low_mean_start_bin_ = Round(kLowMeanStartHz * kFftSize / sample_rate_hz_);
-  low_mean_end_bin_ = Round(kLowMeanEndHz * kFftSize / sample_rate_hz_);
-  high_mean_start_bin_ = Round(kHighMeanStartHz * kFftSize / sample_rate_hz_);
-  high_mean_end_bin_ = Round(kHighMeanEndHz * kFftSize / sample_rate_hz_);
-  // These bin indexes determine the regions over which a mean is taken. This
-  // is applied as a constant value over the adjacent end "frequency correction"
-  // regions.
-  //
-  //             low_mean_start_bin_     high_mean_start_bin_
-  //                   v                         v              constant
-  // |----------------|--------|----------------|-------|----------------|
-  //   constant               ^                        ^
-  //             low_mean_end_bin_       high_mean_end_bin_
-  //
-  RTC_DCHECK_GT(low_mean_start_bin_, 0U);
-  RTC_DCHECK_LT(low_mean_start_bin_, low_mean_end_bin_);
-  RTC_DCHECK_LT(low_mean_end_bin_, high_mean_end_bin_);
-  RTC_DCHECK_LT(high_mean_start_bin_, high_mean_end_bin_);
-  RTC_DCHECK_LT(high_mean_end_bin_, kNumFreqBins - 1);
+  InitFrequencyCorrectionRanges();
 
   high_pass_postfilter_mask_ = 1.f;
   is_target_present_ = false;
@@ -275,6 +252,37 @@ void NonlinearBeamformer::Initialize(int chunk_size_ms, int sample_rate_hz) {
   }
 }
 
+void NonlinearBeamformer::InitFrequencyCorrectionRanges() {
+  const float kAliasingFreqHz =
+      kSpeedOfSoundMeterSeconds /
+      (mic_spacing_ * (1.f + std::abs(std::cos(kTargetAngleRadians))));
+  const float kHighMeanStartHz = std::min(0.5f *  kAliasingFreqHz,
+                                          sample_rate_hz_ / 2.f);
+  const float kHighMeanEndHz = std::min(0.75f *  kAliasingFreqHz,
+                                        sample_rate_hz_ / 2.f);

[Andrew MacDonald, 2015/10/13 22:09:21]

This results in a fairly similar range as before when mic_spacing_ = 0.05. Have
you tested this somewhat less heuristic approach vs our current fully heuristic
approach across a few different devices?

[aluebs-webrtc, 2015/10/17 01:01:22]

Yes, I tested it on all supported Chromebooks.
This change was originally introduced because of the smaller spacing of some
other devices (4mics-2cm).

+
+  low_mean_start_bin_ = Round(kLowMeanStartHz * kFftSize / sample_rate_hz_);
+  low_mean_end_bin_ = Round(kLowMeanEndHz * kFftSize / sample_rate_hz_);
+  high_mean_start_bin_ = Round(kHighMeanStartHz * kFftSize / sample_rate_hz_);
+  high_mean_end_bin_ = Round(kHighMeanEndHz * kFftSize / sample_rate_hz_);
+  // These bin indexes determine the regions over which a mean is taken. This
+  // is applied as a constant value over the adjacent end "frequency correction"
+  // regions.
+  //
+  //             low_mean_start_bin_     high_mean_start_bin_
+  //                   v                         v              constant
+  // |----------------|--------|----------------|-------|----------------|
+  //   constant               ^                        ^
+  //             low_mean_end_bin_       high_mean_end_bin_
+  //
+  RTC_DCHECK_GT(low_mean_start_bin_, 0U);
+  RTC_DCHECK_LT(low_mean_start_bin_, low_mean_end_bin_);
+  RTC_DCHECK_LT(low_mean_end_bin_, high_mean_end_bin_);
+  RTC_DCHECK_LT(high_mean_start_bin_, high_mean_end_bin_);
+  RTC_DCHECK_LT(high_mean_end_bin_, kNumFreqBins - 1);
+}
+
+
 void NonlinearBeamformer::InitInterfAngles() {
   const float kAway =
       std::min(static_cast<float>(M_PI),