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AEC3: High-pass filter delay estimator signals

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This CL applies a high pass filter to the delay estimator signals which
improves the adaptation of the matched filters in noisy environments.
This results in faster delay estimation.

Bug: webrtc:9288
Change-Id: I8ffe5442eab7ac2f10a7ba236b08a0f07ec90645
Reviewed-on: https://webrtc-review.googlesource.com/77725
Commit-Queue: Gustaf Ullberg <gustaf@webrtc.org>
Reviewed-by: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23308}
This commit is contained in:
Gustaf Ullberg 2018-05-18 15:45:09 +02:00 committed by Commit Bot
parent 77995e744b
commit 6bf5a0d5b6
3 changed files with 13 additions and 16 deletions
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13
modules/audio_processing/aec3/decimator.cc
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@ -35,6 +35,12 @@ const CascadedBiQuadFilter::BiQuadCoefficients kLowPassFilterCoefficients8 = {
{-1.56101808f, 0.64135154f}};
constexpr int kNumFilters8 = 4;
// b, a = signal.butter(2, 1000/8000.0, 'highpass', analog=False)
const CascadedBiQuadFilter::BiQuadCoefficients kHighPassFilterCoefficients4 = {
{0.75707638f, -1.51415275f, 0.75707638f},
{-1.45424359f, 0.57406192f}};
constexpr int kNumFiltersHP4 = 1;
} // namespace
Decimator::Decimator(size_t down_sampling_factor)
@ -46,7 +52,8 @@ Decimator::Decimator(size_t down_sampling_factor)
: kLowPassFilterCoefficients2),
down_sampling_factor_ == 4
? kNumFilters4
: (down_sampling_factor_ == 8 ? kNumFilters8 : kNumFilters2)) {
: (down_sampling_factor_ == 8 ? kNumFilters8 : kNumFilters2)),
high_pass_filter_(kHighPassFilterCoefficients4, kNumFiltersHP4) {
RTC_DCHECK(down_sampling_factor_ == 2 || down_sampling_factor_ == 4 ||
down_sampling_factor_ == 8);
}
@ -60,6 +67,10 @@ void Decimator::Decimate(rtc::ArrayView<const float> in,
// Limit the frequency content of the signal to avoid aliasing.
low_pass_filter_.Process(in, x);
// High-pass filter to reduce the impact of near-end noise.
if (down_sampling_factor_ == 4)
high_pass_filter_.Process(x, x);
// Downsample the signal.
for (size_t j = 0, k = 0; j < out.size(); ++j, k += down_sampling_factor_) {
RTC_DCHECK_GT(kBlockSize, k);

1
modules/audio_processing/aec3/decimator.h
View File

@ -31,6 +31,7 @@ class Decimator {
private:
const size_t down_sampling_factor_;
CascadedBiQuadFilter low_pass_filter_;
CascadedBiQuadFilter high_pass_filter_;
RTC_DISALLOW_COPY_AND_ASSIGN(Decimator);
};

15
modules/audio_processing/aec3/decimator_unittest.cc
View File

@ -99,21 +99,6 @@ TEST(Decimator, NoLeakageFromUpperFrequencies) {
}
}
// Verifies that the impact of low-frequency content is small during the
// downsampling.
TEST(Decimator, NoImpactOnLowerFrequencies) {
float input_power;
float output_power;
for (auto rate : {8000, 16000, 32000, 48000}) {
for (auto down_sampling_factor : kDownSamplingFactors) {
ProduceDebugText(rate);
ProduceDecimatedSinusoidalOutputPower(rate, down_sampling_factor, 200.f,
&input_power, &output_power);
EXPECT_LT(0.7f * input_power, output_power);
}
}
}
#if RTC_DCHECK_IS_ON && GTEST_HAS_DEATH_TEST && !defined(WEBRTC_ANDROID)
// Verifies the check for the input size.
TEST(Decimator, WrongInputSize) {