Line data    Source code

       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             : 
      24           0 : MedianSlopeEstimator::MedianSlopeEstimator(size_t window_size,
      25           0 :                                            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           0 :       trendline_(0) {}
      33             : 
      34           0 : MedianSlopeEstimator::~MedianSlopeEstimator() {}
      35             : 
      36           0 : void MedianSlopeEstimator::Update(double recv_delta_ms,
      37             :                                   double send_delta_ms,
      38             :                                   int64_t arrival_time_ms) {
      39           0 :   const double delta_ms = recv_delta_ms - send_delta_ms;
      40           0 :   ++num_of_deltas_;
      41           0 :   if (num_of_deltas_ > kDeltaCounterMax)
      42           0 :     num_of_deltas_ = kDeltaCounterMax;
      43             : 
      44           0 :   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           0 :   if (delay_hist_.size() == window_size_) {
      51           0 :     for (double slope : delay_hist_.front().slopes) {
      52           0 :       const bool success = median_filter_.Erase(slope);
      53           0 :       RTC_CHECK(success);
      54             :     }
      55           0 :     delay_hist_.pop_front();
      56             :   }
      57             :   // Add |window_size_| - 1 new slopes.
      58           0 :   for (auto& old_delay : delay_hist_) {
      59           0 :     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           0 :       double slope = (accumulated_delay_ - old_delay.delay) /
      68           0 :                      static_cast<double>(arrival_time_ms - old_delay.time);
      69           0 :       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           0 :       old_delay.slopes.push_back(slope);
      73             :     }
      74             :   }
      75           0 :   delay_hist_.emplace_back(arrival_time_ms, accumulated_delay_,
      76           0 :                            window_size_ - 1);
      77             :   // Recompute the median slope.
      78           0 :   if (delay_hist_.size() == window_size_)
      79           0 :     trendline_ = median_filter_.GetPercentileValue();
      80             : 
      81             :   BWE_TEST_LOGGING_PLOT(1, "trendline_slope", arrival_time_ms, trendline_);
      82           0 : }
      83             : 
      84             : }  // namespace webrtc