92 lines
3.7 KiB
C++
92 lines
3.7 KiB
C++
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/*
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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(rtc::ArrayView<const float> in,
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rtc::ArrayView<float> out) {
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RTC_DCHECK_EQ(kBlockSize, in.size());
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RTC_DCHECK_EQ(kBlockSize / down_sampling_factor_, out.size());
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std::array<float, kBlockSize> x;
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// Limit the frequency content of the signal to avoid aliasing.
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anti_aliasing_filter_.Process(in, 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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