Make the separation between target and interferer scenario depend on microphone spacing in Nonlinea…

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 6a30cbfbb3272a014f063ca07a7eb4d0c9949357..fec93778d872a6c4b53a0f98de45d0b3095f42d5 100644
--- a/webrtc/modules/audio_processing/beamformer/nonlinear_beamformer.cc
+++ b/webrtc/modules/audio_processing/beamformer/nonlinear_beamformer.cc
@@ -36,6 +36,14 @@ const float kSpeedOfSoundMeterSeconds = 343;
 // TODO(aluebs): Make the target angle dynamically settable.
 const float kTargetAngleRadians = static_cast<float>(M_PI) / 2.f;
 
+// The minimum separation in radians between the target direction and a

[Andrew MacDonald, 2015/10/14 23:38:53]

and an interferer

[aluebs-webrtc, 2015/10/17 00:54:49]

Done.

+// interferer scenario.
+const float kMinAwayRadians = 0.2f;
+
+// The separation between the target direction and the closest interferer
+// scenario is proportional to this constant.
+const float kAwaySlope = 0.008f;
+
 // When calculating the interference covariance matrix, this is the weight for
 // the weighted average between the uniform covariance matrix and the angled
 // covariance matrix.
@@ -183,6 +191,19 @@ std::vector<Point> GetCenteredArray(std::vector<Point> array_geometry) {
   return array_geometry;
 }
 
+float GetMinimumSpacing(std::vector<Point> array_geometry) {

[Andrew MacDonald, 2015/10/14 23:38:53]

const reference

[aluebs-webrtc, 2015/10/17 00:54:50]

Done.

+  float mic_spacing = Distance(array_geometry[0], array_geometry[1]);
+  for (size_t i = 0; i < (array_geometry.size() - 1); ++i) {
+    for (size_t j = i + 1; j < array_geometry.size(); ++j) {
+      float distance = Distance(array_geometry[i], array_geometry[j]);

[Andrew MacDonald, 2015/10/14 23:38:53]

Not a big deal, but you're computing the first distance twice. Perhaps:
float mic_spacing = std::numeric_limits<float>::max();

OTOH, the very common two mic case will then have to enter the loop. Up to you.

[aluebs-webrtc, 2015/10/17 00:54:49]

Good suggestion. Done.

+      if (distance < mic_spacing) {
+        mic_spacing = distance;
+      }
+    }
+  }
+  return mic_spacing;
+}
+
 }  // namespace
 
 // static
@@ -190,8 +211,9 @@ const size_t NonlinearBeamformer::kNumFreqBins;
 
 NonlinearBeamformer::NonlinearBeamformer(
     const std::vector<Point>& array_geometry)
-  : num_input_channels_(array_geometry.size()),
-      array_geometry_(GetCenteredArray(array_geometry)) {
+    : num_input_channels_(array_geometry.size()),
+      array_geometry_(GetCenteredArray(array_geometry)),
+      mic_spacing_(GetMinimumSpacing(array_geometry)) {
   WindowGenerator::KaiserBesselDerived(kKbdAlpha, kFftSize, window_);
 }
 
@@ -254,8 +276,10 @@ void NonlinearBeamformer::Initialize(int chunk_size_ms, int sample_rate_hz) {
 }
 
 void NonlinearBeamformer::InitInterfAngles() {
-  // TODO(aluebs): Make kAway dependent on the mic spacing.
-  const float kAway = 0.5;
+  const float kAway =
+      std::min(static_cast<float>(M_PI),
+               std::max(kMinAwayRadians,
+                        kAwaySlope * static_cast<float>(M_PI) / mic_spacing_));
 
   interf_angles_radians_.clear();
   // TODO(aluebs): When the target angle is settable, make sure the interferer