AEC3: Move decimator filters to the new notation
Preparing for changing the filters of the decimator by moving the old filters to the new zero, pole, gain notation. Bug: webrtc:9288,chromium:846615 Change-Id: I2b01a2555d34617e0bf251c782703753f72cd56f Reviewed-on: https://webrtc-review.googlesource.com/81189 Reviewed-by: Per Åhgren <peah@webrtc.org> Commit-Queue: Gustaf Ullberg <gustaf@webrtc.org> Cr-Commit-Position: refs/heads/master@{#23528}
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Gustaf Ullberg
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@ -15,8 +15,14 @@ namespace webrtc {
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CascadedBiQuadFilter::BiQuadParam::BiQuadParam(std::complex<float> zero,
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std::complex<float> pole,
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float gain)
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: zero(zero), pole(pole), gain(gain) {}
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float gain,
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bool mirror_zero_along_i_axis)
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: zero(zero),
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pole(pole),
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gain(gain),
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mirror_zero_along_i_axis(mirror_zero_along_i_axis) {}
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CascadedBiQuadFilter::BiQuadParam::BiQuadParam(const BiQuadParam&) = default;
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CascadedBiQuadFilter::BiQuad::BiQuad(
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const CascadedBiQuadFilter::BiQuadParam& param)
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@ -27,10 +33,20 @@ CascadedBiQuadFilter::BiQuad::BiQuad(
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float p_i = std::imag(param.pole);
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float gain = param.gain;
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coefficients.b[0] = gain * 1.f;
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coefficients.b[1] = gain * -2.f * z_r;
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coefficients.b[2] = gain * (z_r * z_r + z_i * z_i);
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if (param.mirror_zero_along_i_axis) {
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// Assuming zeroes at z_r and -z_r.
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RTC_DCHECK(z_i == 0.f);
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coefficients.b[0] = gain * 1.f;
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coefficients.b[1] = 0.f;
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coefficients.b[2] = gain * -(z_r * z_r);
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} else {
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// Assuming zeros at (z_r + z_i*i) and (z_r - z_i*i).
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coefficients.b[0] = gain * 1.f;
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coefficients.b[1] = gain * -2.f * z_r;
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coefficients.b[2] = gain * (z_r * z_r + z_i * z_i);
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}
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// Assuming poles at (p_r + p_i*i) and (p_r - p_i*i).
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coefficients.a[0] = -2.f * p_r;
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coefficients.a[1] = p_r * p_r + p_i * p_i;
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}
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@ -24,10 +24,15 @@ namespace webrtc {
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class CascadedBiQuadFilter {
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public:
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struct BiQuadParam {
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BiQuadParam(std::complex<float> zero, std::complex<float> pole, float gain);
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BiQuadParam(std::complex<float> zero,
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std::complex<float> pole,
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float gain,
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bool mirror_zero_along_i_axis = false);
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BiQuadParam(const BiQuadParam&);
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std::complex<float> zero;
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std::complex<float> pole;
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float gain;
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bool mirror_zero_along_i_axis;
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};
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struct BiQuadCoefficients {
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@ -123,4 +123,18 @@ TEST(CascadedBiquadFilter, BiQuadParamHighPass) {
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EXPECT_NEAR(filter.coefficients.a[1], 0.57406192f, epsilon);
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}
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// Verifies the conversion from zero, pole, gain to filter coefficients for
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// bandpass filter.
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TEST(CascadedBiquadFilter, BiQuadParamBandPass) {
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CascadedBiQuadFilter::BiQuadParam param(
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{1.0f, 0.0f}, {1.11022302e-16f, 0.71381051f}, 0.2452372752527856f, true);
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CascadedBiQuadFilter::BiQuad filter(param);
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const float epsilon = 1e-6f;
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EXPECT_NEAR(filter.coefficients.b[0], 0.24523728f, epsilon);
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EXPECT_NEAR(filter.coefficients.b[1], 0.f, epsilon);
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EXPECT_NEAR(filter.coefficients.b[2], -0.24523728f, epsilon);
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EXPECT_NEAR(filter.coefficients.a[0], -2.22044605e-16f, epsilon);
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EXPECT_NEAR(filter.coefficients.a[1], 5.09525449e-01f, epsilon);
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}
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} // namespace webrtc
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@ -14,53 +14,42 @@
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namespace webrtc {
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namespace {
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// b, a = signal.butter(2, 3400/8000.0, 'lowpass', analog=False) which are the
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// same as b, a = signal.butter(2, 1700/4000.0, 'lowpass', analog=False).
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const CascadedBiQuadFilter::BiQuadCoefficients kLowPassFilterCoefficients2 = {
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{0.22711796f, 0.45423593f, 0.22711796f},
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{-0.27666461f, 0.18513647f}};
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constexpr int kNumFilters2 = 3;
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// signal.butter(2, 3400/8000.0, 'lowpass', analog=False)
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const std::vector<CascadedBiQuadFilter::BiQuadParam> kLowPassFilterDS2 = {
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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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// b, a = signal.butter(2, 750/8000.0, 'lowpass', analog=False) which are the
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// same as b, a = signal.butter(2, 375/4000.0, 'lowpass', analog=False).
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const CascadedBiQuadFilter::BiQuadCoefficients kLowPassFilterCoefficients4 = {
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{0.0179f, 0.0357f, 0.0179f},
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{-1.5879f, 0.6594f}};
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constexpr int kNumFilters4 = 3;
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// signal.butter(2, 750/8000.0, 'lowpass', analog=False)
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const std::vector<CascadedBiQuadFilter::BiQuadParam> kLowPassFilterDS4 = {
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{{-1.f, 0.f}, {0.79396855f, 0.17030506f}, 0.017863192751682862f},
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{{-1.f, 0.f}, {0.79396855f, 0.17030506f}, 0.017863192751682862f},
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{{-1.f, 0.f}, {0.79396855f, 0.17030506f}, 0.017863192751682862f}};
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// b, a = signal.cheby1(1, 6, [1000/8000, 2000/8000], btype='bandpass',
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// analog=False)
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const CascadedBiQuadFilter::BiQuadCoefficients kBandPassFilterCoefficients8 = {
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{0.10330478f, 0.f, -0.10330478f},
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{-1.520363f, 0.79339043f}};
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constexpr int kNumFilters8 = 5;
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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> kBandPassFilterDS8 = {
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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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// b, a = signal.butter(2, 1000/8000.0, 'highpass', analog=False)
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const CascadedBiQuadFilter::BiQuadCoefficients kHighPassFilterCoefficients = {
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{0.75707638f, -1.51415275f, 0.75707638f},
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{-1.45424359f, 0.57406192f}};
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constexpr int kNumFiltersHP2 = 1;
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constexpr int kNumFiltersHP4 = 1;
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constexpr int kNumFiltersHP8 = 0;
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// signal.butter(2, 1000/8000.0, 'highpass', analog=False)
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const std::vector<CascadedBiQuadFilter::BiQuadParam> kHighPassFilter = {
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{{1.f, 0.f}, {0.72712179f, 0.21296904f}, 0.7570763753338849f}};
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const std::vector<CascadedBiQuadFilter::BiQuadParam> kPassThroughFilter = {};
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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_(
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down_sampling_factor_ == 4
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? kLowPassFilterCoefficients4
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: (down_sampling_factor_ == 8 ? kBandPassFilterCoefficients8
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: kLowPassFilterCoefficients2),
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down_sampling_factor_ == 4
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? kNumFilters4
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: (down_sampling_factor_ == 8 ? kNumFilters8 : kNumFilters2)),
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noise_reduction_filter_(
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kHighPassFilterCoefficients,
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down_sampling_factor_ == 4
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? kNumFiltersHP4
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: (down_sampling_factor_ == 8 ? kNumFiltersHP8
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: kNumFiltersHP2)) {
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anti_aliasing_filter_(down_sampling_factor_ == 4
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? kLowPassFilterDS4
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: (down_sampling_factor_ == 8
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? kBandPassFilterDS8
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: kLowPassFilterDS2)),
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noise_reduction_filter_(down_sampling_factor_ == 8 ? kPassThroughFilter
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: kHighPassFilter) {
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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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