Cast: Reduce bitrate drastically when close to unacked frame limit

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 84 matching lines @@
   void ResendFrame(uint32 resend_frame_id);
   void ReceivedAck(uint32 acked_frame_id);
   void UpdateFramesInFlight();
 
   void SendEncodedVideoFrameMainThread(
       scoped_ptr<transport::EncodedVideoFrame> encoded_frame,
       const base::TimeTicks& capture_time);
 
   void InitializeTimers();
 
+  void UpdateBitrate(int32 new_bitrate);
+
   base::TimeDelta rtp_max_delay_;
   const int max_frame_rate_;
 
   scoped_refptr<CastEnvironment> cast_environment_;
   transport::CastTransportSender* const transport_sender_;
 
   // Subscribes to raw events.
   // Processes raw audio events to be sent over to the cast receiver via RTCP.
   SenderRtcpEventSubscriber event_subscriber_;
   RtpSenderStatistics rtp_stats_;
   scoped_ptr<LocalRtcpVideoSenderFeedback> rtcp_feedback_;
   scoped_ptr<VideoEncoder> video_encoder_;
   scoped_ptr<Rtcp> rtcp_;
   uint8 max_unacked_frames_;
   int last_acked_frame_id_;
   int last_sent_frame_id_;
   int frames_in_encoder_;
   int duplicate_ack_;
   base::TimeTicks last_send_time_;
   base::TimeTicks last_checked_skip_count_time_;
   int last_skip_count_;
   int current_requested_bitrate_;
+  // 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.
+  int current_bitrate_divider_;
   CongestionControl congestion_control_;
 
   // 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.
   RtpTimestamp frame_id_to_rtp_timestamp_[256];
 
   bool initialized_;
   // Indicator for receiver acknowledgments.
   bool active_session_;
 
   // 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_