text: /*
   *  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 <utility>
  
  #include "api/network_state_predictor.h"
  #include "api/webrtc_key_value_config.h"
  #include "congestion_controller/delay_increase_detector_interface.h"
  #include "remote_bitrate_estimator/bwe_defines.h"
  #include "rtc_base/constructor_magic.h"
  #include "rtc_base/struct_parameters_parser.h"
  
  namespace webrtc {
  
  struct BweIgnoreSmallPacketsSettings {
    static constexpr char kKey[] = "WebRTC-BweIgnoreSmallPackets";
  
    BweIgnoreSmallPacketsSettings() = default;
    explicit BweIgnoreSmallPacketsSettings(
        const WebRtcKeyValueConfig* key_value_config);
  
    double smoothing_factor = 0.1;
    double min_fraction_large_packets = 1.0;
    unsigned large_packet_size = 0;
    unsigned ignored_size = 0;
  
    std::unique_ptr<StructParametersParser> Parser();
  };
  
  class TrendlineEstimator : public DelayIncreaseDetectorInterface {
   public:
    TrendlineEstimator(const WebRtcKeyValueConfig* key_value_config,
                       NetworkStatePredictor* network_state_predictor);
  
    ~TrendlineEstimator() override;
  
    // 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;
  
   private:
    friend class GoogCcStatePrinter;
  
    void Detect(double trend, double ts_delta, int64_t now_ms);
  
    void UpdateThreshold(double modified_offset, int64_t now_ms);
  
    // Filtering out small packets. (Intention is to base the detection only
    // on video packets even if we have TWCC sequence number for audio.)
    BweIgnoreSmallPacketsSettings ignore_small_packets_;
    double fraction_large_packets_;
  
    // Parameters.
    const size_t window_size_;
    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<std::pair<double, double>> 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_;
  
    RTC_DISALLOW_COPY_AND_ASSIGN(TrendlineEstimator);
  };
  }  // namespace webrtc
  
  #endif  // MODULES_CONGESTION_CONTROLLER_GOOG_CC_TRENDLINE_ESTIMATOR_H_
  