Cast: First stab at implementing adaptive latency

media/cast/sender/frame_sender.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 is the base class for an object that send frames to a receiver.
 // TODO(hclam): Refactor such that there is no separate AudioSender vs.
 // VideoSender, and the functionality of both is rolled into this class.
 
 #ifndef MEDIA_CAST_SENDER_FRAME_SENDER_H_
 #define MEDIA_CAST_SENDER_FRAME_SENDER_H_
@@ skipping 11 matching lines @@
 
 class FrameSender {
  public:
   FrameSender(scoped_refptr<CastEnvironment> cast_environment,
               bool is_audio,
               CastTransportSender* const transport_sender,
               base::TimeDelta rtcp_interval,
               int rtp_timebase,
               uint32 ssrc,
               double max_frame_rate,
-              base::TimeDelta playout_delay,
+              base::TimeDelta min_playout_delay,
+              base::TimeDelta max_playout_delay,
               CongestionControl* congestion_control);
   virtual ~FrameSender();
 
   // Calling this function is only valid if the receiver supports the
   // "extra_playout_delay", rtp extension.
   void SetTargetPlayoutDelay(base::TimeDelta new_target_playout_delay);
 
   base::TimeDelta GetTargetPlayoutDelay() const {
     return target_playout_delay_;
   }
 
   // Called by the encoder with the next EncodeFrame to send.
   void SendEncodedFrame(int requested_bitrate_before_encode,
                         scoped_ptr<EncodedFrame> encoded_frame);
 
  protected:
   // Returns the number of frames in the encoder's backlog.
   virtual int GetNumberOfFramesInEncoder() const = 0;
 
   // Called when we get an ACK for a frame.
   virtual void OnAck(uint32 frame_id) = 0;
 
  protected:
   // Schedule and execute periodic sending of RTCP report.
   void ScheduleNextRtcpReport();
   void SendRtcpReport(bool schedule_future_reports);
 
   void OnMeasuredRoundTripTime(base::TimeDelta rtt);
+  base::TimeDelta AverageRTT();
 
   const scoped_refptr<CastEnvironment> cast_environment_;
 
   // Sends encoded frames over the configured transport (e.g., UDP).  In
   // Chromium, this could be a proxy that first sends the frames from a renderer
   // process to the browser process over IPC, with the browser process being
   // responsible for "packetizing" the frames and pushing packets into the
   // network layer.
   CastTransportSender* const transport_sender_;
 
@@ skipping 30 matching lines @@
 
   const base::TimeDelta rtcp_interval_;
 
   // The total amount of time between a frame's capture/recording on the sender
   // and its playback on the receiver (i.e., shown to a user).  This is fixed as
   // a value large enough to give the system sufficient time to encode,
   // transmit/retransmit, receive, decode, and render; given its run-time
   // environment (sender/receiver hardware performance, network conditions,
   // etc.).
   base::TimeDelta target_playout_delay_;
+  base::TimeDelta min_playout_delay_;
+  base::TimeDelta max_playout_delay_;
 
   // If true, we transmit the target playout delay to the receiver.
   bool send_target_playout_delay_;
 
   // Max encoded frames generated per second.
   double max_frame_rate_;
 
   // Maximum number of outstanding frames before the encoding and sending of
   // new frames shall halt.
   int max_unacked_frames_;
@@ skipping 39 matching lines @@
 
   // Ring buffers to keep track of recent frame timestamps (both in terms of
   // local reference time and RTP media time).  These should only be accessed
   // through the Record/GetXXX() methods.
   base::TimeTicks frame_reference_times_[256];
   RtpTimestamp frame_rtp_timestamps_[256];
 
   // The most recently measured round trip time.
   base::TimeDelta current_round_trip_time_;
 
+  // Used to keep track of historic round-trip times.
+  std::deque<base::TimeDelta> recent_round_trip_times_;
+  base::TimeDelta recent_round_trip_times_sum_;
+
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<FrameSender> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(FrameSender);
 };
 
 }  // namespace cast
 }  // namespace media
 
 #endif  // MEDIA_CAST_SENDER_FRAME_SENDER_H_