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Apply mask smoothing in Beamformer

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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
This commit is contained in:
aluebs@webrtc.org 2015-02-10 18:23:06 +00:00
parent 8da96ac0f6
commit b6856d2823
2 changed files with 7 additions and 10 deletions
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14
webrtc/modules/audio_processing/beamformer/beamformer.cc
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@ -58,8 +58,8 @@ const float kBoxcarHalfWidth = 0.001f;
// 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 @@ Beamformer::Beamformer(const std::vector<Point>& array_geometry)
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 @@ void Beamformer::ProcessAudioBlock(const complex_f* const* input,
// Can't access block_index - 1 on the first block.
if (previous_block_ix_ >= 0) {
ApplyDecay();
ApplyMaskSmoothing();
}
ApplyLowFrequencyCorrection();
@ -430,13 +428,13 @@ void Beamformer::ApplyMasks(const complex_f* const* input,
}
}
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];
}
}

3
webrtc/modules/audio_processing/beamformer/beamformer.h
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@ -83,7 +83,7 @@ class Beamformer : public LappedTransform::Callback {
// 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 @@ class Beamformer : public LappedTransform::Callback {
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_;