[Cast] Halt AudioSender transmission when too many frames are in-flight.

media/cast/video_sender/video_sender.h

 // Copyright 2013 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.
 
 #ifndef MEDIA_CAST_VIDEO_SENDER_VIDEO_SENDER_H_
 #define MEDIA_CAST_VIDEO_SENDER_VIDEO_SENDER_H_
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 58 matching lines @@
  protected:
   // Protected for testability.
   virtual void OnReceivedCastFeedback(const RtcpCastMessage& cast_feedback)
       OVERRIDE;
 
  private:
   // Schedule and execute periodic sending of RTCP report.
   void ScheduleNextRtcpReport();
   void SendRtcpReport(bool schedule_future_reports);
 
-  // Schedule and execute periodic checks for re-sending frames.  If no
+  // Schedule and execute periodic checks for re-sending packets.  If no
   // acknowledgements have been received for "too long," VideoSender will
-  // speculatively re-send the frame just after |latest_acked_frame_id_| (the
-  // whole frame).  This is a last resort tactic to prevent the session from
+  // speculatively re-send certain packets of an unacked frame to kick-start
+  // re-transmission.  This is a last resort tactic to prevent the session from
   // getting stuck after a long outage.
   void ScheduleNextResendCheck();
   void ResendCheck();
-
-  // Resend certain packets of an unacked frame to kick start re-transmission.
   void ResendForKickstart();
 
   // Returns true if there are too many frames in flight, as defined by the
   // configured target playout delay plus simple logic.  When this is true,
   // InsertRawVideoFrame() will silenty drop frames instead of sending them to
   // the video encoder.
   bool AreTooManyFramesInFlight() const;
 
   // Called by the |video_encoder_| with the next EncodeFrame to send.
   void SendEncodedVideoFrame(int requested_bitrate_before_encode,
@@ skipping 64 matching lines @@
   // When we get close to the max number of un-acked frames, we set lower
   // the bitrate drastically to ensure that we catch up. Without this we
   // risk getting stuck in a catch-up state forever.
   CongestionControl congestion_control_;
 
   // If this sender is ready for use, this is STATUS_VIDEO_INITIALIZED.
   CastInitializationStatus cast_initialization_status_;
 
   // This is a "good enough" mapping for finding the RTP timestamp associated
   // with a video frame. The key is the lowest 8 bits of frame id (which is
-  // what is sent via RTCP). This map is used for logging purposes. The only
-  // time when this mapping will be incorrect is when it receives an ACK for a
-  // old enough frame such that 8-bit wrap around has already occurred, which
-  // should be pretty rare.
+  // what is sent via RTCP). This map is used for logging purposes.
   RtpTimestamp frame_id_to_rtp_timestamp_[256];
 
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<VideoSender> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(VideoSender);
 };
 
 }  // namespace cast
 }  // namespace media
 
 #endif  // MEDIA_CAST_VIDEO_SENDER_VIDEO_SENDER_H_