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             : #ifndef WEBRTC_MODULES_CONGESTION_CONTROLLER_TRENDLINE_ESTIMATOR_H_
      11             : #define WEBRTC_MODULES_CONGESTION_CONTROLLER_TRENDLINE_ESTIMATOR_H_
      12             : 
      13             : #include <stddef.h>
      14             : #include <stdint.h>
      15             : 
      16             : #include <list>
      17             : #include <utility>
      18             : 
      19             : #include "webrtc/base/constructormagic.h"
      20             : 
      21             : namespace webrtc {
      22             : 
      23             : class TrendlineEstimator {
      24             :  public:
      25             :   // |window_size| is the number of points required to compute a trend line.
      26             :   // |smoothing_coef| controls how much we smooth out the delay before fitting
      27             :   // the trend line. |threshold_gain| is used to scale the trendline slope for
      28             :   // comparison to the old threshold. Once the old estimator has been removed
      29             :   // (or the thresholds been merged into the estimators), we can just set the
      30             :   // threshold instead of setting a gain.
      31             :   TrendlineEstimator(size_t window_size,
      32             :                      double smoothing_coef,
      33             :                      double threshold_gain);
      34             :   ~TrendlineEstimator();
      35             : 
      36             :   // Update the estimator with a new sample. The deltas should represent deltas
      37             :   // between timestamp groups as defined by the InterArrival class.
      38             :   void Update(double recv_delta_ms,
      39             :               double send_delta_ms,
      40             :               int64_t arrival_time_ms);
      41             : 
      42             :   // Returns the estimated trend k multiplied by some gain.
      43             :   // 0 < k < 1   ->  the delay increases, queues are filling up
      44             :   //   k == 0    ->  the delay does not change
      45             :   //   k < 0     ->  the delay decreases, queues are being emptied
      46           0 :   double trendline_slope() const { return trendline_ * threshold_gain_; }
      47             : 
      48             :   // Returns the number of deltas which the current estimator state is based on.
      49           0 :   unsigned int num_of_deltas() const { return num_of_deltas_; }
      50             : 
      51             :  private:
      52             :   // Parameters.
      53             :   const size_t window_size_;
      54             :   const double smoothing_coef_;
      55             :   const double threshold_gain_;
      56             :   // Used by the existing threshold.
      57             :   unsigned int num_of_deltas_;
      58             :   // Keep the arrival times small by using the change from the first packet.
      59             :   int64_t first_arrival_time_ms;
      60             :   // Exponential backoff filtering.
      61             :   double accumulated_delay_;
      62             :   double smoothed_delay_;
      63             :   // Linear least squares regression.
      64             :   std::list<std::pair<double, double>> delay_hist_;
      65             :   double trendline_;
      66             : 
      67             :   RTC_DISALLOW_COPY_AND_ASSIGN(TrendlineEstimator);
      68             : };
      69             : }  // namespace webrtc
      70             : 
      71             : #endif  // WEBRTC_MODULES_CONGESTION_CONTROLLER_TRENDLINE_ESTIMATOR_H_