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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_ANALYTICS_EXP_FILTER_H_ | |
12 #define WEBRTC_BASE_ANALYTICS_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_ANALYTICS_EXP_FILTER_H_ | |
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