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ee84d39fce
Multichannel signals are downmixed to mono before decimation and delay estimation. This is useful when not all channels play audio content. The feature can be toggled in the AEC3 configuration. Bug: webrtc:10913 Change-Id: I7d40edf7732bb51fec69e7f3ca063d821c5069c4 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/151762 Commit-Queue: Gustaf Ullberg <gustaf@webrtc.org> Reviewed-by: Per Åhgren <peah@webrtc.org> Cr-Commit-Position: refs/heads/master@{#29126}
109 lines
4.3 KiB
C++
109 lines
4.3 KiB
C++
/*
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* Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "modules/audio_processing/aec3/decimator.h"
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#include <array>
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#include <vector>
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#include "modules/audio_processing/aec3/aec3_common.h"
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#include "rtc_base/checks.h"
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namespace webrtc {
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namespace {
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// signal.butter(2, 3400/8000.0, 'lowpass', analog=False)
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const std::vector<CascadedBiQuadFilter::BiQuadParam> GetLowPassFilterDS2() {
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return std::vector<CascadedBiQuadFilter::BiQuadParam>{
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{{-1.f, 0.f}, {0.13833231f, 0.40743176f}, 0.22711796393486466f},
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{{-1.f, 0.f}, {0.13833231f, 0.40743176f}, 0.22711796393486466f},
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{{-1.f, 0.f}, {0.13833231f, 0.40743176f}, 0.22711796393486466f}};
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}
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// signal.ellip(6, 1, 40, 1800/8000, btype='lowpass', analog=False)
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const std::vector<CascadedBiQuadFilter::BiQuadParam> GetLowPassFilterDS4() {
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return std::vector<CascadedBiQuadFilter::BiQuadParam>{
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{{-0.08873842f, 0.99605496f}, {0.75916227f, 0.23841065f}, 0.26250696827f},
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{{0.62273832f, 0.78243018f}, {0.74892112f, 0.5410152f}, 0.26250696827f},
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{{0.71107693f, 0.70311421f}, {0.74895534f, 0.63924616f}, 0.26250696827f}};
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}
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// signal.cheby1(1, 6, [1000/8000, 2000/8000], btype='bandpass', analog=False)
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const std::vector<CascadedBiQuadFilter::BiQuadParam> GetBandPassFilterDS8() {
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return std::vector<CascadedBiQuadFilter::BiQuadParam>{
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{{1.f, 0.f}, {0.7601815f, 0.46423542f}, 0.10330478266505948f, true},
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{{1.f, 0.f}, {0.7601815f, 0.46423542f}, 0.10330478266505948f, true},
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{{1.f, 0.f}, {0.7601815f, 0.46423542f}, 0.10330478266505948f, true},
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{{1.f, 0.f}, {0.7601815f, 0.46423542f}, 0.10330478266505948f, true},
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{{1.f, 0.f}, {0.7601815f, 0.46423542f}, 0.10330478266505948f, true}};
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}
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// signal.butter(2, 1000/8000.0, 'highpass', analog=False)
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const std::vector<CascadedBiQuadFilter::BiQuadParam> GetHighPassFilter() {
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return std::vector<CascadedBiQuadFilter::BiQuadParam>{
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{{1.f, 0.f}, {0.72712179f, 0.21296904f}, 0.7570763753338849f}};
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}
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const std::vector<CascadedBiQuadFilter::BiQuadParam> GetPassThroughFilter() {
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return std::vector<CascadedBiQuadFilter::BiQuadParam>{};
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}
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} // namespace
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Decimator::Decimator(size_t down_sampling_factor)
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: down_sampling_factor_(down_sampling_factor),
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anti_aliasing_filter_(down_sampling_factor_ == 4
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? GetLowPassFilterDS4()
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: (down_sampling_factor_ == 8
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? GetBandPassFilterDS8()
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: GetLowPassFilterDS2())),
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noise_reduction_filter_(down_sampling_factor_ == 8
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? GetPassThroughFilter()
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: GetHighPassFilter()) {
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RTC_DCHECK(down_sampling_factor_ == 2 || down_sampling_factor_ == 4 ||
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down_sampling_factor_ == 8);
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}
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void Decimator::Decimate(const std::vector<std::vector<float>>& in,
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bool downmix,
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rtc::ArrayView<float> out) {
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RTC_DCHECK_EQ(kBlockSize, in[0].size());
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RTC_DCHECK_EQ(kBlockSize / down_sampling_factor_, out.size());
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std::array<float, kBlockSize> in_downmixed;
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std::array<float, kBlockSize> x;
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// Mix channels before decimation.
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std::copy(in[0].begin(), in[0].end(), in_downmixed.begin());
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if (downmix && in.size() > 1) {
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for (size_t channel = 1; channel < in.size(); channel++) {
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const auto& data = in[channel];
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for (size_t i = 0; i < kBlockSize; i++) {
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in_downmixed[i] += data[i];
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}
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}
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const float one_by_num_channels = 1.f / in.size();
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for (size_t i = 0; i < kBlockSize; i++) {
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in_downmixed[i] *= one_by_num_channels;
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}
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}
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// Limit the frequency content of the signal to avoid aliasing.
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anti_aliasing_filter_.Process(in_downmixed, x);
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// Reduce the impact of near-end noise.
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noise_reduction_filter_.Process(x);
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// Downsample the signal.
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for (size_t j = 0, k = 0; j < out.size(); ++j, k += down_sampling_factor_) {
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RTC_DCHECK_GT(kBlockSize, k);
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out[j] = x[k];
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}
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}
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} // namespace webrtc
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