trendline_estimator.h

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/*

 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.

 *  Use of this source code is governed by a BSD-style license

 *  that can be found in the LICENSE file in the root of the source

 *  tree. An additional intellectual property rights grant can be found

 *  in the file PATENTS.  All contributing project authors may

 *  be found in the AUTHORS file in the root of the source tree.

*/

#ifndef MODULES_CONGESTION_CONTROLLER_GOOG_CC_TRENDLINE_ESTIMATOR_H_

#define MODULES_CONGESTION_CONTROLLER_GOOG_CC_TRENDLINE_ESTIMATOR_H_

#include <stddef.h>

#include <stdint.h>

#include <deque>

#include <memory>

#include "api/field_trials_view.h"

#include "api/network_state_predictor.h"

#include "api/transport/bandwidth_usage.h"

#include "modules/congestion_controller/goog_cc/delay_increase_detector_interface.h"

#include "rtc_base/experiments/struct_parameters_parser.h"

namespace webrtc {

struct TrendlineEstimatorSettings {

  static constexpr char kKey[] = "WebRTC-Bwe-TrendlineEstimatorSettings";

  static constexpr unsigned kDefaultTrendlineWindowSize = 20;

  TrendlineEstimatorSettings() = delete;

  explicit TrendlineEstimatorSettings(const FieldTrialsView* key_value_config);

  // Sort the packets in the window. Should be redundant,

  // but then almost no cost.

  bool enable_sort = false;

  // Cap the trendline slope based on the minimum delay seen

  // in the beginning_packets and end_packets respectively.

  bool enable_cap = false;

  unsigned beginning_packets = 7;

  unsigned end_packets = 7;

  double cap_uncertainty = 0.0;

  // Size (in packets) of the window.

  unsigned window_size = kDefaultTrendlineWindowSize;

  std::unique_ptr<StructParametersParser> Parser();

};

class TrendlineEstimator : public DelayIncreaseDetectorInterface {

 public:

  TrendlineEstimator(const FieldTrialsView* key_value_config,

                     NetworkStatePredictor* network_state_predictor);

  ~TrendlineEstimator() override;

  TrendlineEstimator(const TrendlineEstimator&) = delete;

  TrendlineEstimator& operator=(const TrendlineEstimator&) = delete;

  // Update the estimator with a new sample. The deltas should represent deltas

  // between timestamp groups as defined by the InterArrival class.

  void Update(double recv_delta_ms,

              double send_delta_ms,

              int64_t send_time_ms,

              int64_t arrival_time_ms,

              size_t packet_size,

              bool calculated_deltas) override;

  void UpdateTrendline(double recv_delta_ms,

                       double send_delta_ms,

                       int64_t send_time_ms,

                       int64_t arrival_time_ms,

                       size_t packet_size);

  BandwidthUsage State() const override;

  struct PacketTiming {

    PacketTiming(double arrival_time_ms,

                 double smoothed_delay_ms,

                 double raw_delay_ms)

        : arrival_time_ms(arrival_time_ms),

          smoothed_delay_ms(smoothed_delay_ms),

          raw_delay_ms(raw_delay_ms) {}

    double arrival_time_ms;

    double smoothed_delay_ms;

    double raw_delay_ms;

};

 private:

  friend class GoogCcStatePrinter;

  void Detect(double trend, double ts_delta, int64_t now_ms);

  void UpdateThreshold(double modified_offset, int64_t now_ms);

  // Parameters.

  TrendlineEstimatorSettings settings_;

  const double smoothing_coef_;

  const double threshold_gain_;

  // Used by the existing threshold.

  int num_of_deltas_;

  // Keep the arrival times small by using the change from the first packet.

  int64_t first_arrival_time_ms_;

  // Exponential backoff filtering.

  double accumulated_delay_;

  double smoothed_delay_;

  // Linear least squares regression.

  std::deque<PacketTiming> delay_hist_;

  const double k_up_;

  const double k_down_;

  double overusing_time_threshold_;

  double threshold_;

  double prev_modified_trend_;

  int64_t last_update_ms_;

  double prev_trend_;

  double time_over_using_;

  int overuse_counter_;

  BandwidthUsage hypothesis_;

  BandwidthUsage hypothesis_predicted_;

  NetworkStatePredictor* network_state_predictor_;

};

}  // namespace webrtc

#endif  // MODULES_CONGESTION_CONTROLLER_GOOG_CC_TRENDLINE_ESTIMATOR_H_