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             : #include "webrtc/modules/audio_processing/level_controller/biquad_filter.h"
      12             : 
      13             : namespace webrtc {
      14             : 
      15             : // This method applies a biquad filter to an input signal x to produce an
      16             : // output signal y. The biquad coefficients are specified at the construction
      17             : // of the object.
      18           0 : void BiQuadFilter::Process(rtc::ArrayView<const float> x,
      19             :                            rtc::ArrayView<float> y) {
      20           0 :   for (size_t k = 0; k < x.size(); ++k) {
      21             :     // Use temporary variable for x[k] to allow in-place function call
      22             :     // (that x and y refer to the same array).
      23           0 :     const float tmp = x[k];
      24           0 :     y[k] = coefficients_.b[0] * tmp + coefficients_.b[1] * biquad_state_.b[0] +
      25           0 :            coefficients_.b[2] * biquad_state_.b[1] -
      26           0 :            coefficients_.a[0] * biquad_state_.a[0] -
      27           0 :            coefficients_.a[1] * biquad_state_.a[1];
      28           0 :     biquad_state_.b[1] = biquad_state_.b[0];
      29           0 :     biquad_state_.b[0] = tmp;
      30           0 :     biquad_state_.a[1] = biquad_state_.a[0];
      31           0 :     biquad_state_.a[0] = y[k];
      32             :   }
      33           0 : }
      34             : 
      35             : }  // namespace webrtc