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| 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) |
| 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. |
| 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_ |
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