Apply mask smoothing in Beamformer
This generates much more aggressive postfilter masks, which remove the interference and background noise better.
R=andrew@webrtc.org
Review URL: https://webrtc-codereview.appspot.com/35089004
Cr-Commit-Position: refs/heads/master@{#8315}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8315 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/modules/audio_processing/beamformer/beamformer.cc b/webrtc/modules/audio_processing/beamformer/beamformer.cc
index 09aa312..a2c20b5 100644
--- a/webrtc/modules/audio_processing/beamformer/beamformer.cc
+++ b/webrtc/modules/audio_processing/beamformer/beamformer.cc
@@ -58,8 +58,8 @@
// that our covariance matrices are positive semidefinite.
const float kCovUniformGapHalfWidth = 0.001f;
-// Lower bound on gain decay.
-const float kHalfLifeSeconds = 0.05f;
+// Alpha coefficient for mask smoothing.
+const float kMaskSmoothAlpha = 0.2f;
// The average mask is computed from masks in this mid-frequency range.
const int kLowAverageStartHz = 200;
@@ -151,8 +151,6 @@
void Beamformer::Initialize(int chunk_size_ms, int sample_rate_hz) {
chunk_length_ = sample_rate_hz / (1000.f / chunk_size_ms);
sample_rate_hz_ = sample_rate_hz;
- decay_threshold_ =
- pow(2, (kFftSize / -2.f) / (sample_rate_hz_ * kHalfLifeSeconds));
low_average_start_bin_ =
Round(kLowAverageStartHz * kFftSize / sample_rate_hz_);
low_average_end_bin_ =
@@ -379,7 +377,7 @@
// Can't access block_index - 1 on the first block.
if (previous_block_ix_ >= 0) {
- ApplyDecay();
+ ApplyMaskSmoothing();
}
ApplyLowFrequencyCorrection();
@@ -430,13 +428,13 @@
}
}
-void Beamformer::ApplyDecay() {
+void Beamformer::ApplyMaskSmoothing() {
float* current_mask_els = postfilter_masks_[current_block_ix_].elements()[0];
const float* previous_block_els =
postfilter_masks_[previous_block_ix_].elements()[0];
for (int i = 0; i < kNumFreqBins; ++i) {
- current_mask_els[i] =
- std::max(current_mask_els[i], previous_block_els[i] * decay_threshold_);
+ current_mask_els[i] = kMaskSmoothAlpha * current_mask_els[i] +
+ (1.f - kMaskSmoothAlpha) * previous_block_els[i];
}
}
diff --git a/webrtc/modules/audio_processing/beamformer/beamformer.h b/webrtc/modules/audio_processing/beamformer/beamformer.h
index ef25088..574e121 100644
--- a/webrtc/modules/audio_processing/beamformer/beamformer.h
+++ b/webrtc/modules/audio_processing/beamformer/beamformer.h
@@ -83,7 +83,7 @@
// Prevents the postfilter masks from degenerating too quickly (a cause of
// musical noise).
- void ApplyDecay();
+ void ApplyMaskSmoothing();
// The postfilter masks are unreliable at low frequencies. Calculates a better
// mask by averaging mid-low frequency values.
@@ -119,7 +119,6 @@
const float mic_spacing_;
// Calculated based on user-input and constants in the .cc file.
- float decay_threshold_;
int low_average_start_bin_;
int low_average_end_bin_;
int high_average_start_bin_;
