1 /*
2 * libjingle
3 * Copyright 2011, Google Inc.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are met:
7 *
8 * 1. Redistributions of source code must retain the above copyright notice,
9 * this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright notice,
11 * this list of conditions and the following disclaimer in the documentation
12 * and/or other materials provided with the distribution.
13 * 3. The name of the author may not be used to endorse or promote products
14 * derived from this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
17 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
18 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
19 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
20 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
21 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
22 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
23 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
24 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
25 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 */
27
28 #include "talk/base/bandwidthsmoother.h"
29
30 #include <limits.h>
31
32 namespace talk_base {
33
BandwidthSmoother(int initial_bandwidth_guess,uint32 time_between_increase,double percent_increase,size_t samples_count_to_average,double min_sample_count_percent)34 BandwidthSmoother::BandwidthSmoother(int initial_bandwidth_guess,
35 uint32 time_between_increase,
36 double percent_increase,
37 size_t samples_count_to_average,
38 double min_sample_count_percent)
39 : time_between_increase_(time_between_increase),
40 percent_increase_(talk_base::_max(1.0, percent_increase)),
41 time_at_last_change_(0),
42 bandwidth_estimation_(initial_bandwidth_guess),
43 accumulator_(samples_count_to_average),
44 min_sample_count_percent_(
45 talk_base::_min(1.0,
46 talk_base::_max(0.0, min_sample_count_percent))) {
47 }
48
49 // Samples a new bandwidth measurement
50 // returns true if the bandwidth estimation changed
Sample(uint32 sample_time,int bandwidth)51 bool BandwidthSmoother::Sample(uint32 sample_time, int bandwidth) {
52 if (bandwidth < 0) {
53 return false;
54 }
55
56 accumulator_.AddSample(bandwidth);
57
58 if (accumulator_.count() < static_cast<size_t>(
59 accumulator_.max_count() * min_sample_count_percent_)) {
60 // We have not collected enough samples yet.
61 return false;
62 }
63
64 // Replace bandwidth with the mean of sampled bandwidths.
65 const int mean_bandwidth = static_cast<int>(accumulator_.ComputeMean());
66
67 if (mean_bandwidth < bandwidth_estimation_) {
68 time_at_last_change_ = sample_time;
69 bandwidth_estimation_ = mean_bandwidth;
70 return true;
71 }
72
73 const int old_bandwidth_estimation = bandwidth_estimation_;
74 const double increase_threshold_d = percent_increase_ * bandwidth_estimation_;
75 if (increase_threshold_d > INT_MAX) {
76 // If bandwidth goes any higher we would overflow.
77 return false;
78 }
79
80 const int increase_threshold = static_cast<int>(increase_threshold_d);
81 if (mean_bandwidth < increase_threshold) {
82 time_at_last_change_ = sample_time;
83 // The value of bandwidth_estimation remains the same if we don't exceed
84 // percent_increase_ * bandwidth_estimation_ for at least
85 // time_between_increase_ time.
86 } else if (sample_time >= time_at_last_change_ + time_between_increase_) {
87 time_at_last_change_ = sample_time;
88 if (increase_threshold == 0) {
89 // Bandwidth_estimation_ must be zero. Assume a jump from zero to a
90 // positive bandwidth means we have regained connectivity.
91 bandwidth_estimation_ = mean_bandwidth;
92 } else {
93 bandwidth_estimation_ = increase_threshold;
94 }
95 }
96 // Else don't make a change.
97
98 return old_bandwidth_estimation != bandwidth_estimation_;
99 }
100
101 } // namespace talk_base
102