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 
Reset(float alpha)19 void ExpFilter::Reset(float alpha) {
20   alpha_ = alpha;
21   filtered_ = kValueUndefined;
22 }
23 
Apply(float exp,float sample)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 
UpdateBase(float alpha)40 void ExpFilter::UpdateBase(float alpha) {
41   alpha_ = alpha;
42 }
43 }  // namespace rtc
44