1 /*
2 * Copyright 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/bandwidthsmoother.h"
12
13 #include <limits.h>
14 #include <algorithm>
15
16 namespace rtc {
17
BandwidthSmoother(int initial_bandwidth_guess,uint32_t time_between_increase,double percent_increase,size_t samples_count_to_average,double min_sample_count_percent)18 BandwidthSmoother::BandwidthSmoother(int initial_bandwidth_guess,
19 uint32_t time_between_increase,
20 double percent_increase,
21 size_t samples_count_to_average,
22 double min_sample_count_percent)
23 : time_between_increase_(time_between_increase),
24 percent_increase_(std::max(1.0, percent_increase)),
25 time_at_last_change_(0),
26 bandwidth_estimation_(initial_bandwidth_guess),
27 accumulator_(samples_count_to_average),
28 min_sample_count_percent_(
29 std::min(1.0, std::max(0.0, min_sample_count_percent))) {
30 }
31
32 BandwidthSmoother::~BandwidthSmoother() = default;
33
34 // Samples a new bandwidth measurement
35 // returns true if the bandwidth estimation changed
Sample(uint32_t sample_time,int bandwidth)36 bool BandwidthSmoother::Sample(uint32_t sample_time, int bandwidth) {
37 if (bandwidth < 0) {
38 return false;
39 }
40
41 accumulator_.AddSample(bandwidth);
42
43 if (accumulator_.count() < static_cast<size_t>(
44 accumulator_.max_count() * min_sample_count_percent_)) {
45 // We have not collected enough samples yet.
46 return false;
47 }
48
49 // Replace bandwidth with the mean of sampled bandwidths.
50 const int mean_bandwidth = static_cast<int>(accumulator_.ComputeMean());
51
52 if (mean_bandwidth < bandwidth_estimation_) {
53 time_at_last_change_ = sample_time;
54 bandwidth_estimation_ = mean_bandwidth;
55 return true;
56 }
57
58 const int old_bandwidth_estimation = bandwidth_estimation_;
59 const double increase_threshold_d = percent_increase_ * bandwidth_estimation_;
60 if (increase_threshold_d > INT_MAX) {
61 // If bandwidth goes any higher we would overflow.
62 return false;
63 }
64
65 const int increase_threshold = static_cast<int>(increase_threshold_d);
66 if (mean_bandwidth < increase_threshold) {
67 time_at_last_change_ = sample_time;
68 // The value of bandwidth_estimation remains the same if we don't exceed
69 // percent_increase_ * bandwidth_estimation_ for at least
70 // time_between_increase_ time.
71 } else if (sample_time >= time_at_last_change_ + time_between_increase_) {
72 time_at_last_change_ = sample_time;
73 if (increase_threshold == 0) {
74 // Bandwidth_estimation_ must be zero. Assume a jump from zero to a
75 // positive bandwidth means we have regained connectivity.
76 bandwidth_estimation_ = mean_bandwidth;
77 } else {
78 bandwidth_estimation_ = increase_threshold;
79 }
80 }
81 // Else don't make a change.
82
83 return old_bandwidth_estimation != bandwidth_estimation_;
84 }
85
86 } // namespace rtc
87