1 /*
2 * Copyright (c) 2016 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/modules/congestion_controller/median_slope_estimator.h"
12
13 #include <algorithm>
14 #include <vector>
15
16 #include "webrtc/base/logging.h"
17 #include "webrtc/modules/remote_bitrate_estimator/include/bwe_defines.h"
18 #include "webrtc/modules/remote_bitrate_estimator/test/bwe_test_logging.h"
19
20 namespace webrtc {
21
22 constexpr unsigned int kDeltaCounterMax = 1000;
23
MedianSlopeEstimator(size_t window_size,double threshold_gain)24 MedianSlopeEstimator::MedianSlopeEstimator(size_t window_size,
25 double threshold_gain)
26 : window_size_(window_size),
27 threshold_gain_(threshold_gain),
28 num_of_deltas_(0),
29 accumulated_delay_(0),
30 delay_hist_(),
31 median_filter_(0.5),
32 trendline_(0) {}
33
~MedianSlopeEstimator()34 MedianSlopeEstimator::~MedianSlopeEstimator() {}
35
Update(double recv_delta_ms,double send_delta_ms,int64_t arrival_time_ms)36 void MedianSlopeEstimator::Update(double recv_delta_ms,
37 double send_delta_ms,
38 int64_t arrival_time_ms) {
39 const double delta_ms = recv_delta_ms - send_delta_ms;
40 ++num_of_deltas_;
41 if (num_of_deltas_ > kDeltaCounterMax)
42 num_of_deltas_ = kDeltaCounterMax;
43
44 accumulated_delay_ += delta_ms;
45 BWE_TEST_LOGGING_PLOT(1, "accumulated_delay_ms", arrival_time_ms,
46 accumulated_delay_);
47
48 // If the window is full, remove the |window_size_| - 1 slopes that belong to
49 // the oldest point.
50 if (delay_hist_.size() == window_size_) {
51 for (double slope : delay_hist_.front().slopes) {
52 const bool success = median_filter_.Erase(slope);
53 RTC_CHECK(success);
54 }
55 delay_hist_.pop_front();
56 }
57 // Add |window_size_| - 1 new slopes.
58 for (auto& old_delay : delay_hist_) {
59 if (arrival_time_ms - old_delay.time != 0) {
60 // The C99 standard explicitly states that casts and assignments must
61 // perform the associated conversions. This means that |slope| will be
62 // a 64-bit double even if the division is computed using, e.g., 80-bit
63 // extended precision. I believe this also holds in C++ even though the
64 // C++11 standard isn't as explicit. Furthermore, there are good reasons
65 // to believe that compilers couldn't perform optimizations that break
66 // this assumption even if they wanted to.
67 double slope = (accumulated_delay_ - old_delay.delay) /
68 static_cast<double>(arrival_time_ms - old_delay.time);
69 median_filter_.Insert(slope);
70 // We want to avoid issues with different rounding mode / precision
71 // which we might get if we recomputed the slope when we remove it.
72 old_delay.slopes.push_back(slope);
73 }
74 }
75 delay_hist_.emplace_back(arrival_time_ms, accumulated_delay_,
76 window_size_ - 1);
77 // Recompute the median slope.
78 if (delay_hist_.size() == window_size_)
79 trendline_ = median_filter_.GetPercentileValue();
80
81 BWE_TEST_LOGGING_PLOT(1, "trendline_slope", arrival_time_ms, trendline_);
82 }
83
84 } // namespace webrtc
85