bandwidthsmoother.cc revision 0c4e06b4c6107a1b94f764e279e4fb4161e905b0 
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
16namespace rtc {
17
18BandwidthSmoother::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
32BandwidthSmoother::~BandwidthSmoother() = default;
33
34// Samples a new bandwidth measurement
35// returns true if the bandwidth estimation changed
36bool 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