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/*
* 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.
*/
#ifndef MODULES_AUDIO_PROCESSING_UTILITY_CASCADED_BIQUAD_FILTER_H_
#define MODULES_AUDIO_PROCESSING_UTILITY_CASCADED_BIQUAD_FILTER_H_
#include <stddef.h>
#include <complex>
#include <vector>
#include "api/array_view.h"
namespace webrtc {
// Applies a number of biquads in a cascaded manner. The filter implementation
// is direct form 1.
class CascadedBiQuadFilter {
public:
struct BiQuadParam {
BiQuadParam(std::complex<float> zero,
std::complex<float> pole,
float gain,
bool mirror_zero_along_i_axis = false);
explicit BiQuadParam(const BiQuadParam&);
std::complex<float> zero;
std::complex<float> pole;
float gain;
bool mirror_zero_along_i_axis;
};
struct BiQuadCoefficients {
float b[3];
float a[2];
};
struct BiQuad {
explicit BiQuad(const BiQuadCoefficients& coefficients)
: coefficients(coefficients), x(), y() {}
explicit BiQuad(const CascadedBiQuadFilter::BiQuadParam& param);
void Reset();
BiQuadCoefficients coefficients;
float x[2];
float y[2];
};
CascadedBiQuadFilter(
const CascadedBiQuadFilter::BiQuadCoefficients& coefficients,
size_t num_biquads);
explicit CascadedBiQuadFilter(
const std::vector<CascadedBiQuadFilter::BiQuadParam>& biquad_params);
~CascadedBiQuadFilter();
CascadedBiQuadFilter(const CascadedBiQuadFilter&) = delete;
CascadedBiQuadFilter& operator=(const CascadedBiQuadFilter&) = delete;
// Applies the biquads on the values in x in order to form the output in y.
void Process(rtc::ArrayView<const float> x, rtc::ArrayView<float> y);
// Applies the biquads on the values in y in an in-place manner.
void Process(rtc::ArrayView<float> y);
// Resets the filter to its initial state.
void Reset();
private:
void ApplyBiQuad(rtc::ArrayView<const float> x,
rtc::ArrayView<float> y,
CascadedBiQuadFilter::BiQuad* biquad);
std::vector<BiQuad> biquads_;
};
} // namespace webrtc
#endif // MODULES_AUDIO_PROCESSING_UTILITY_CASCADED_BIQUAD_FILTER_H_
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