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 #include "webrtc/base/exp_filter.h" 12 13 #include <math.h> 14 15 namespace rtc { 16 17 const float ExpFilter::kValueUndefined = -1.0f; 18 19 void ExpFilter::Reset(float alpha) { 20 alpha_ = alpha; 21 filtered_ = kValueUndefined; 22 } 23 24 float ExpFilter::Apply(float exp, float sample) { 25 if (filtered_ == kValueUndefined) { 26 // Initialize filtered value. 27 filtered_ = sample; 28 } else if (exp == 1.0) { 29 filtered_ = alpha_ * filtered_ + (1 - alpha_) * sample; 30 } else { 31 float alpha = pow(alpha_, exp); 32 filtered_ = alpha * filtered_ + (1 - alpha) * sample; 33 } 34 if (max_ != kValueUndefined && filtered_ > max_) { 35 filtered_ = max_; 36 } 37 return filtered_; 38 } 39 40 void ExpFilter::UpdateBase(float alpha) { 41 alpha_ = alpha; 42 } 43 } // namespace rtc 44
