[Cast] RTT clean-up to the max!

media/cast/net/rtcp/rtcp.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This class maintains a bi-directional RTCP connection with a remote
 // peer.
 
 #ifndef MEDIA_CAST_RTCP_RTCP_H_
 #define MEDIA_CAST_RTCP_RTCP_H_
 
@@ skipping 71 matching lines @@
       base::TimeDelta target_delay,
       const ReceiverRtcpEventSubscriber::RtcpEventMultiMap* rtcp_events,
       RtpReceiverStatistics* rtp_receiver_statistics);
 
   // Submit a received packet to this object. The packet will be parsed
   // and used to maintain a RTCP session.
   // Returns false if this is not a RTCP packet or it is not directed to
   // this session, e.g. SSRC doesn't match.
   bool IncomingRtcpPacket(const uint8* data, size_t length);
 
-  // TODO(miu): Clean up this method and downstream code: Only VideoSender uses
-  // this (for congestion control), and only the |rtt| and |avg_rtt| values, and
-  // it's not clear that any of the downstream code is doing the right thing
-  // with this data.
-  bool Rtt(base::TimeDelta* rtt,
-           base::TimeDelta* avg_rtt,
-           base::TimeDelta* min_rtt,
-           base::TimeDelta* max_rtt) const;
-
   // If available, returns true and sets the output arguments to the latest
   // lip-sync timestamps gleaned from the sender reports.  While the sender
   // provides reference NTP times relative to its own wall clock, the
   // |reference_time| returned here has been translated to the local
   // CastEnvironment clock.
   bool GetLatestLipSyncTimes(uint32* rtp_timestamp,
                              base::TimeTicks* reference_time) const;
 
   void OnReceivedReceiverLog(const RtcpReceiverLogMessage& receiver_log);
 
+  // If greater than zero, this is the last measured network round trip time.
+  base::TimeDelta current_round_trip_time() const {
+    return current_round_trip_time_;
+  }
+
   static bool IsRtcpPacket(const uint8* packet, size_t length);
   static uint32 GetSsrcOfSender(const uint8* rtcp_buffer, size_t length);
-  const base::TimeDelta& rtt() const { return rtt_; }
 
  protected:
   void OnReceivedNtp(uint32 ntp_seconds, uint32 ntp_fraction);
   void OnReceivedLipSyncInfo(uint32 rtp_timestamp,
                              uint32 ntp_seconds,
                              uint32 ntp_fraction);
 
  private:
   void OnReceivedDelaySinceLastReport(uint32 last_report,
                                       uint32 delay_since_last_report);
 
   void OnReceivedCastFeedback(const RtcpCastMessage& cast_message);
 
-  void UpdateRtt(const base::TimeDelta& sender_delay,
-                 const base::TimeDelta& receiver_delay);
-
   void SaveLastSentNtpTime(const base::TimeTicks& now,
                            uint32 last_ntp_seconds,
                            uint32 last_ntp_fraction);
 
   // Remove duplicate events in |receiver_log|.
   // Returns true if any events remain.
   bool DedupeReceiverLog(RtcpReceiverLogMessage* receiver_log);
 
   const RtcpCastMessageCallback cast_callback_;
   const RtcpRttCallback rtt_callback_;
@@ skipping 20 matching lines @@
   ClockDriftSmoother local_clock_ahead_by_;
 
   // Latest "lip sync" info from the sender.  The sender provides the RTP
   // timestamp of some frame of its choosing and also a corresponding reference
   // NTP timestamp sampled from a clock common to all media streams.  It is
   // expected that the sender will update this data regularly and in a timely
   // manner (e.g., about once per second).
   uint32 lip_sync_rtp_timestamp_;
   uint64 lip_sync_ntp_timestamp_;
 
-  base::TimeDelta rtt_;
-  base::TimeDelta min_rtt_;
-  base::TimeDelta max_rtt_;
-  int number_of_rtt_in_avg_;
-  base::TimeDelta avg_rtt_;
+  // The last measured network round trip time.  This is updated with each
+  // sender report --> receiver report round trip.  If this is zero, then the
+  // round trip time has not been measured yet.
+  base::TimeDelta current_round_trip_time_;
 
   base::TimeTicks largest_seen_timestamp_;
 
   // For extending received ACK frame IDs from 8-bit to 32-bit.
   FrameIdWrapHelper ack_frame_id_wrap_helper_;
 
   // Maintains a history of receiver events.
   typedef std::pair<uint64, uint64> ReceiverEventKey;
   base::hash_set<ReceiverEventKey> receiver_event_key_set_;
   std::queue<ReceiverEventKey> receiver_event_key_queue_;
 
   DISALLOW_COPY_AND_ASSIGN(Rtcp);
 };
 
 }  // namespace cast
 }  // namespace media
 
 #endif  // MEDIA_CAST_RTCP_RTCP_H_