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_MODULES_VIDEO_CODING_UTILITY_INCLUDE_EXP_FILTER_H_ 12 #define WEBRTC_MODULES_VIDEO_CODING_UTILITY_INCLUDE_EXP_FILTER_H_ 13 14 namespace webrtc 15 { 16 17 /**********************/ 18 /* ExpFilter class */ 19 /**********************/ 20 21 class VCMExpFilter 22 { 23 public: 24 VCMExpFilter(float alpha, float max = -1.0) : _alpha(alpha), _filtered(-1.0), _max(max) {} 25 26 // Resets the filter to its initial state, and resets alpha to the given value 27 // 28 // Input: 29 // - alpha : the new value of the filter factor base. 30 void Reset(float alpha); 31 32 // Applies the filter with the given exponent on the provided sample 33 // 34 // Input: 35 // - exp : Exponent T in y(k) = alpha^T * y(k-1) + (1 - alpha^T) * x(k) 36 // - sample : x(k) in the above filter equation 37 float Apply(float exp, float sample); 38 39 // Return current filtered value: y(k) 40 // 41 // Return value : The current filter output 42 float Value() const; 43 44 // Change the filter factor base 45 // 46 // Input: 47 // - alpha : The new filter factor base. 48 void UpdateBase(float alpha); 49 50 private: 51 float _alpha; // Filter factor base 52 float _filtered; // Current filter output 53 const float _max; 54 }; // end of ExpFilter class 55 56 } // namespace webrtc 57 58 #endif // WEBRTC_MODULES_VIDEO_CODING_UTILITY_INCLUDE_EXP_FILTER_H_ 59
