Add probing to recover faster from large bitrate drops.

webrtc/modules/congestion_controller/delay_based_bwe.h

 /*
  *  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.
  */
 
@@ skipping 18 matching lines @@
 
 namespace webrtc {
 
 class RtcEventLog;
 
 class DelayBasedBwe {
  public:
   static const int64_t kStreamTimeOutMs = 2000;
 
   struct Result {
-    Result() : updated(false), probe(false), target_bitrate_bps(0) {}
-    Result(bool probe, uint32_t target_bitrate_bps)
-        : updated(true), probe(probe), target_bitrate_bps(target_bitrate_bps) {}
+    Result();
+    Result(bool probe, uint32_t target_bitrate_bps);
+    Result(bool probe,
+           uint32_t target_bitrate_bps,
+           uint32_t suggested_probe_bps);
+    ~Result();
     bool updated;
     bool probe;
     uint32_t target_bitrate_bps;
+    rtc::Optional<uint32_t> suggested_probe_bps;
   };
 
   DelayBasedBwe(RtcEventLog* event_log, const Clock* clock);
   virtual ~DelayBasedBwe();
 
   Result IncomingPacketFeedbackVector(
       const std::vector<PacketFeedback>& packet_feedback_vector,
       rtc::Optional<uint32_t> acked_bitrate_bps);
   void OnRttUpdate(int64_t avg_rtt_ms, int64_t max_rtt_ms);
   bool LatestEstimate(std::vector<uint32_t>* ssrcs,
                       uint32_t* bitrate_bps) const;
   void SetStartBitrate(int start_bitrate_bps);
   void SetMinBitrate(int min_bitrate_bps);
   int64_t GetExpectedBwePeriodMs() const;
 
  private:
   void IncomingPacketFeedback(const PacketFeedback& packet_feedback);
   Result OnLongFeedbackDelay(int64_t arrival_time_ms);
-
   Result MaybeUpdateEstimate(bool overusing,
-                             rtc::Optional<uint32_t> acked_bitrate_bps);
+                             rtc::Optional<uint32_t> acked_bitrate_bps,
+                             bool request_probe);
   // Updates the current remote rate estimate and returns true if a valid
   // estimate exists.
   bool UpdateEstimate(int64_t now_ms,
                       rtc::Optional<uint32_t> acked_bitrate_bps,
                       bool overusing,
                       uint32_t* target_bitrate_bps);
 
   rtc::RaceChecker network_race_;
   RtcEventLog* const event_log_;
   const Clock* const clock_;
   std::unique_ptr<InterArrival> inter_arrival_;
   std::unique_ptr<TrendlineEstimator> trendline_estimator_;
   OveruseDetector detector_;
   int64_t last_seen_packet_ms_;
   bool uma_recorded_;
   AimdRateControl rate_control_;
   ProbeBitrateEstimator probe_bitrate_estimator_;
   size_t trendline_window_size_;
   double trendline_smoothing_coeff_;
   double trendline_threshold_gain_;
   int consecutive_delayed_feedbacks_;
+  uint32_t bitrate_before_last_large_drop_;
+  int64_t time_of_last_large_drop_ms_;
   uint32_t last_logged_bitrate_;
   BandwidthUsage last_logged_state_;
   bool in_sparse_update_experiment_;
 
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(DelayBasedBwe);
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_CONGESTION_CONTROLLER_DELAY_BASED_BWE_H_