Line data    Source code

       1             : /*
       2             :  *  Copyright (c) 2011 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_BASE_NUMERICS_EXP_FILTER_H_
      12             : #define WEBRTC_BASE_NUMERICS_EXP_FILTER_H_
      13             : 
      14             : namespace rtc {
      15             : 
      16             : // This class can be used, for example, for smoothing the result of bandwidth
      17             : // estimation and packet loss estimation.
      18             : 
      19             : class ExpFilter {
      20             :  public:
      21             :   static const float kValueUndefined;
      22             : 
      23           0 :   explicit ExpFilter(float alpha, float max = kValueUndefined) : max_(max) {
      24           0 :     Reset(alpha);
      25           0 :   }
      26             : 
      27             :   // Resets the filter to its initial state, and resets filter factor base to
      28             :   // the given value |alpha|.
      29             :   void Reset(float alpha);
      30             : 
      31             :   // Applies the filter with a given exponent on the provided sample:
      32             :   // y(k) = min(alpha_^ exp * y(k-1) + (1 - alpha_^ exp) * sample, max_).
      33             :   float Apply(float exp, float sample);
      34             : 
      35             :   // Returns current filtered value.
      36           0 :   float filtered() const { return filtered_; }
      37             : 
      38             :   // Changes the filter factor base to the given value |alpha|.
      39             :   void UpdateBase(float alpha);
      40             : 
      41             :  private:
      42             :   float alpha_;     // Filter factor base.
      43             :   float filtered_;  // Current filter output.
      44             :   const float max_;
      45             : };
      46             : }  // namespace rtc
      47             : 
      48             : #endif  // WEBRTC_BASE_NUMERICS_EXP_FILTER_H_