Line data    Source code

       1             : /*
       2             :  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
       3             :  *
       4             :  *  Use of this source code is governed by a BSD-style license
       5             :  *  that can be found in the LICENSE file in the root of the source
       6             :  *  tree. An additional intellectual property rights grant can be found
       7             :  *  in the file PATENTS.  All contributing project authors may
       8             :  *  be found in the AUTHORS file in the root of the source tree.
       9             :  */
      10             : 
      11             : #ifndef WEBRTC_MODULES_AUDIO_PROCESSING_AEC3_CASCADED_BIQUAD_FILTER_H_
      12             : #define WEBRTC_MODULES_AUDIO_PROCESSING_AEC3_CASCADED_BIQUAD_FILTER_H_
      13             : 
      14             : #include <vector>
      15             : 
      16             : #include "webrtc/base/array_view.h"
      17             : #include "webrtc/base/constructormagic.h"
      18             : 
      19             : namespace webrtc {
      20             : 
      21             : // Applies a number of identical biquads in a cascaded manner. The filter
      22             : // implementation is direct form 1.
      23           0 : class CascadedBiQuadFilter {
      24             :  public:
      25             :   struct BiQuadState {
      26           0 :     BiQuadState() : x(), y() {}
      27             :     float x[2];
      28             :     float y[2];
      29             :   };
      30             : 
      31             :   struct BiQuadCoefficients {
      32             :     float b[3];
      33             :     float a[2];
      34             :   };
      35             : 
      36             :   CascadedBiQuadFilter(
      37             :       const CascadedBiQuadFilter::BiQuadCoefficients& coefficients,
      38             :       size_t num_biquads);
      39             :   ~CascadedBiQuadFilter();
      40             :   // Applies the biquads on the values in x in order to form the output in y.
      41             :   void Process(rtc::ArrayView<const float> x, rtc::ArrayView<float> y);
      42             :   // Applies the biquads on the values in y in an in-place manner.
      43             :   void Process(rtc::ArrayView<float> y);
      44             : 
      45             :  private:
      46             :   void ApplyBiQuad(rtc::ArrayView<const float> x,
      47             :                    rtc::ArrayView<float> y,
      48             :                    CascadedBiQuadFilter::BiQuadState* biquad_state);
      49             : 
      50             :   std::vector<BiQuadState> biquad_states_;
      51             :   const BiQuadCoefficients coefficients_;
      52             : 
      53             :   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(CascadedBiQuadFilter);
      54             : };
      55             : 
      56             : }  // namespace webrtc
      57             : 
      58             : #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_AEC3_CASCADED_BIQUAD_FILTER_H_