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_EXP_FILTER_H_ 12 #define WEBRTC_BASE_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 explicit ExpFilter(float alpha, float max = kValueUndefined) max_(max)24 : max_(max) { 25 Reset(alpha); 26 } 27 28 // Resets the filter to its initial state, and resets filter factor base to 29 // the given value |alpha|. 30 void Reset(float alpha); 31 32 // Applies the filter with a given exponent on the provided sample: 33 // y(k) = min(alpha_^ exp * y(k-1) + (1 - alpha_^ exp) * sample, max_). 34 float Apply(float exp, float sample); 35 36 // Returns current filtered value. filtered()37 float filtered() const { return filtered_; } 38 39 // Changes the filter factor base to the given value |alpha|. 40 void UpdateBase(float alpha); 41 42 private: 43 float alpha_; // Filter factor base. 44 float filtered_; // Current filter output. 45 const float max_; 46 }; 47 } // namespace rtc 48 49 #endif // WEBRTC_BASE_EXP_FILTER_H_ 50