| /* |
| * Copyright (c) 2016 The WebRTC project authors. All Rights Reserved. |
| * |
| * Use of this source code is governed by a BSD-style license |
| * that can be found in the LICENSE file in the root of the source |
| * tree. An additional intellectual property rights grant can be found |
| * in the file PATENTS. All contributing project authors may |
| * be found in the AUTHORS file in the root of the source tree. |
| */ |
| #include "modules/audio_processing/utility/cascaded_biquad_filter.h" |
| |
| #include <algorithm> |
| |
| #include "rtc_base/checks.h" |
| |
| namespace webrtc { |
| |
| CascadedBiQuadFilter::BiQuadParam::BiQuadParam(std::complex<float> zero, |
| std::complex<float> pole, |
| float gain, |
| bool mirror_zero_along_i_axis) |
| : zero(zero), |
| pole(pole), |
| gain(gain), |
| mirror_zero_along_i_axis(mirror_zero_along_i_axis) {} |
| |
| CascadedBiQuadFilter::BiQuadParam::BiQuadParam(const BiQuadParam&) = default; |
| |
| CascadedBiQuadFilter::BiQuad::BiQuad( |
| const CascadedBiQuadFilter::BiQuadParam& param) |
| : x(), y() { |
| float z_r = std::real(param.zero); |
| float z_i = std::imag(param.zero); |
| float p_r = std::real(param.pole); |
| float p_i = std::imag(param.pole); |
| float gain = param.gain; |
| |
| if (param.mirror_zero_along_i_axis) { |
| // Assuming zeroes at z_r and -z_r. |
| RTC_DCHECK(z_i == 0.f); |
| coefficients.b[0] = gain * 1.f; |
| coefficients.b[1] = 0.f; |
| coefficients.b[2] = gain * -(z_r * z_r); |
| } else { |
| // Assuming zeros at (z_r + z_i*i) and (z_r - z_i*i). |
| coefficients.b[0] = gain * 1.f; |
| coefficients.b[1] = gain * -2.f * z_r; |
| coefficients.b[2] = gain * (z_r * z_r + z_i * z_i); |
| } |
| |
| // Assuming poles at (p_r + p_i*i) and (p_r - p_i*i). |
| coefficients.a[0] = -2.f * p_r; |
| coefficients.a[1] = p_r * p_r + p_i * p_i; |
| } |
| |
| void CascadedBiQuadFilter::BiQuad::BiQuad::Reset() { |
| x[0] = x[1] = y[0] = y[1] = 0.f; |
| } |
| |
| CascadedBiQuadFilter::CascadedBiQuadFilter( |
| const CascadedBiQuadFilter::BiQuadCoefficients& coefficients, |
| size_t num_biquads) |
| : biquads_(num_biquads, BiQuad(coefficients)) {} |
| |
| CascadedBiQuadFilter::CascadedBiQuadFilter( |
| const std::vector<CascadedBiQuadFilter::BiQuadParam>& biquad_params) { |
| for (const auto& param : biquad_params) { |
| biquads_.push_back(BiQuad(param)); |
| } |
| } |
| |
| CascadedBiQuadFilter::~CascadedBiQuadFilter() = default; |
| |
| void CascadedBiQuadFilter::Process(rtc::ArrayView<const float> x, |
| rtc::ArrayView<float> y) { |
| if (biquads_.size() > 0) { |
| ApplyBiQuad(x, y, &biquads_[0]); |
| for (size_t k = 1; k < biquads_.size(); ++k) { |
| ApplyBiQuad(y, y, &biquads_[k]); |
| } |
| } else { |
| std::copy(x.begin(), x.end(), y.begin()); |
| } |
| } |
| |
| void CascadedBiQuadFilter::Process(rtc::ArrayView<float> y) { |
| for (auto& biquad : biquads_) { |
| ApplyBiQuad(y, y, &biquad); |
| } |
| } |
| |
| void CascadedBiQuadFilter::Reset() { |
| for (auto& biquad : biquads_) { |
| biquad.Reset(); |
| } |
| } |
| |
| void CascadedBiQuadFilter::ApplyBiQuad(rtc::ArrayView<const float> x, |
| rtc::ArrayView<float> y, |
| CascadedBiQuadFilter::BiQuad* biquad) { |
| RTC_DCHECK_EQ(x.size(), y.size()); |
| const float c_a_0 = biquad->coefficients.a[0]; |
| const float c_a_1 = biquad->coefficients.a[1]; |
| const float c_b_0 = biquad->coefficients.b[0]; |
| const float c_b_1 = biquad->coefficients.b[1]; |
| const float c_b_2 = biquad->coefficients.b[2]; |
| float m_x_0 = biquad->x[0]; |
| float m_x_1 = biquad->x[1]; |
| float m_y_0 = biquad->y[0]; |
| float m_y_1 = biquad->y[1]; |
| for (size_t k = 0; k < x.size(); ++k) { |
| const float tmp = x[k]; |
| y[k] = c_b_0 * tmp + c_b_1 * m_x_0 + c_b_2 * m_x_1 - c_a_0 * m_y_0 - |
| c_a_1 * m_y_1; |
| m_x_1 = m_x_0; |
| m_x_0 = tmp; |
| m_y_1 = m_y_0; |
| m_y_0 = y[k]; |
| } |
| biquad->x[0] = m_x_0; |
| biquad->x[1] = m_x_1; |
| biquad->y[0] = m_y_0; |
| biquad->y[1] = m_y_1; |
| } |
| |
| } // namespace webrtc |