[Cast] Refactor/clean-up VideoReceiver to match AudioReceiver as closely as possible.

media/cast/video_receiver/video_receiver.h

Index: media/cast/video_receiver/video_receiver.h
diff --git a/media/cast/video_receiver/video_receiver.h b/media/cast/video_receiver/video_receiver.h
index b0c636faab9671b8ad2d4106f5880e6b18a6e3bf..7f3ca232faca55d3d3e323d067beb98e42607f7c 100644
--- a/media/cast/video_receiver/video_receiver.h
+++ b/media/cast/video_receiver/video_receiver.h
@@ -16,6 +16,7 @@
 #include "media/cast/cast_config.h"
 #include "media/cast/cast_environment.h"
 #include "media/cast/cast_receiver.h"
+#include "media/cast/framer/framer.h"
 #include "media/cast/rtcp/receiver_rtcp_event_subscriber.h"
 #include "media/cast/rtcp/rtcp.h"
 #include "media/cast/rtp_receiver/rtp_receiver.h"
@@ -23,70 +24,94 @@
 #include "media/cast/transport/utility/transport_encryption_handler.h"
 
 namespace media {
+
+class VideoFrame;
+
 namespace cast {
 
-class Framer;
-class LocalRtpVideoFeedback;
-class PeerVideoReceiver;
-class Rtcp;
-class RtpReceiverStatistics;
 class VideoDecoder;
 
-// Callback used by the video receiver to inform the audio receiver of the new
-// delay used to compute the playout and render times.
-typedef base::Callback<void(base::TimeDelta)> SetTargetDelayCallback;
-
-// Should only be called from the Main cast thread.
-class VideoReceiver : public base::NonThreadSafe,
-                      public base::SupportsWeakPtr<VideoReceiver>,
-                      public RtpReceiver {
+// VideoReceiver receives packets out-of-order while clients make requests for
+// complete frames in-order.  (A frame consists of one or more packets.)
+//
+// VideoReceiver also includes logic for computing the playout time for each
+// frame, accounting for a constant targeted playout delay.  The purpose of the
+// playout delay is to provide a fixed window of time between the capture event
+// on the sender and the playout on the receiver.  This is important because
+// each step of the pipeline (i.e., encode frame, then transmit/retransmit from
+// the sender, then receive and re-order packets on the receiver, then decode
+// frame) can vary in duration and is typically very hard to predict.
+// Heuristics will determine when the targeted playout delay is insufficient in
+// the current environment; and the receiver can then increase the playout
+// delay, notifying the sender, to account for the extra variance.
+// TODO(miu): Make the last sentence true.  http://crbug.com/360111
+//
+// Two types of frames can be requested: 1) A frame of decoded video data; or 2)
+// a frame of still-encoded video data, to be passed into an external video
+// decoder.  Each request for a frame includes a callback which VideoReceiver
+// guarantees will be called at some point in the future.  Clients should
+// generally limit the number of outstanding requests (perhaps to just one or
+// two).  When VideoReceiver is destroyed, any outstanding requests will be
+// immediately invoked with a NULL frame.
+//
+// This class is not thread safe.  Should only be called from the Main cast
+// thread.
+class VideoReceiver : public RtpReceiver,
+                      public RtpPayloadFeedback,
+                      public base::NonThreadSafe,
+                      public base::SupportsWeakPtr<VideoReceiver> {
  public:
   VideoReceiver(scoped_refptr<CastEnvironment> cast_environment,
                 const VideoReceiverConfig& video_config,
-                transport::PacedPacketSender* const packet_sender,
-                const SetTargetDelayCallback& target_delay_cb);
+                transport::PacedPacketSender* const packet_sender);
 
   virtual ~VideoReceiver();
 
-  // Request a raw frame. Will return frame via callback when available.
+  // Request a decoded video frame.
+  //
+  // The given |callback| is guaranteed to be run at some point in the future,
+  // even if to respond with NULL at shutdown time.
   void GetRawVideoFrame(const VideoFrameDecodedCallback& callback);
 
-  // Request an encoded frame. Will return frame via callback when available.
+  // Request an encoded video frame.
+  //
+  // The given |callback| is guaranteed to be run at some point in the future,
+  // even if to respond with NULL at shutdown time.
   void GetEncodedVideoFrame(const VideoFrameEncodedCallback& callback);
 
-  // Insert a RTP packet to the video receiver.
+  // Deliver another packet, possibly a duplicate, and possibly out-of-order.
   void IncomingPacket(scoped_ptr<Packet> packet);
 
+ protected:
+  friend class VideoReceiverTest;  // Invoked OnReceivedPayloadData().
+
   virtual void OnReceivedPayloadData(const uint8* payload_data,
                                      size_t payload_size,
                                      const RtpCastHeader& rtp_header) OVERRIDE;
 
- protected:
-  void DecodeVideoFrameThread(
-      scoped_ptr<transport::EncodedVideoFrame> encoded_frame,
-      const base::TimeTicks render_time,
-      const VideoFrameDecodedCallback& frame_decoded_callback);
+  // RtpPayloadFeedback implementation.
+  virtual void CastFeedback(const RtcpCastMessage& cast_message) OVERRIDE;
 
  private:
-  friend class LocalRtpVideoFeedback;
-
-  void CastFeedback(const RtcpCastMessage& cast_message);
-
-  void DecodeVideoFrame(const VideoFrameDecodedCallback& callback,
-                        scoped_ptr<transport::EncodedVideoFrame> encoded_frame,
-                        const base::TimeTicks& render_time);
-
-  bool DecryptVideoFrame(scoped_ptr<transport::EncodedVideoFrame>* video_frame);
-
-  bool PullEncodedVideoFrame(
-      bool next_frame,
-      scoped_ptr<transport::EncodedVideoFrame>* encoded_frame,
-      base::TimeTicks* render_time);
-
-  void PlayoutTimeout();
+  // Processes ready-to-consume packets from |framer_|, decrypting each packet's
+  // payload data, and then running the enqueued callbacks in order (one for
+  // each packet).  This method may post a delayed task to re-invoke itself in
+  // the future to wait for missing/incomplete frames.
+  void EmitAvailableEncodedFrames();
+
+  // Clears the |is_waiting_for_consecutive_frame_| flag and invokes
+  // EmitAvailableEncodedFrames().
+  void EmitAvailableEncodedFramesAfterWaiting();
+
+  // Feeds an EncodedVideoFrame into |video_decoder_|.  GetRawVideoFrame() uses
+  // this as a callback for GetEncodedVideoFrame().
+  void DecodeEncodedVideoFrame(
+      const VideoFrameDecodedCallback& callback,
+      scoped_ptr<transport::EncodedVideoFrame> encoded_frame,
+      const base::TimeTicks& playout_time);
 
-  // Returns Render time based on current time and the rtp timestamp.
-  base::TimeTicks GetRenderTime(base::TimeTicks now, uint32 rtp_timestamp);
+  // Return the playout time based on the current time and rtp timestamp.
+  base::TimeTicks GetPlayoutTime(base::TimeTicks now, uint32 rtp_timestamp);
 
   void InitializeTimers();
 
@@ -102,32 +127,45 @@ class VideoReceiver : public base::NonThreadSafe,
   // Actually send the next RTCP report.
   void SendNextRtcpReport();
 
-  // Update the target delay based on past information. Will also update the
-  // rtcp module and the audio receiver.
-  void UpdateTargetDelay();
-
-  scoped_ptr<VideoDecoder> video_decoder_;
-  scoped_refptr<CastEnvironment> cast_environment_;
+  // Receives a VideoFrame from |video_decoder_|, logs the event, and passes the
+  // data on by running the given |callback|.  This method is static to ensure
+  // it can be called after a VideoReceiver instance is destroyed.
+  // DecodeEncodedVideoFrame() uses this as a callback for
+  // VideoDecoder::DecodeFrame().
+  static void EmitRawVideoFrame(
+      const scoped_refptr<CastEnvironment>& cast_environment,
+      const VideoFrameDecodedCallback& callback,
+      uint32 frame_id,
+      uint32 rtp_timestamp,
+      const base::TimeTicks& playout_time,
+      const scoped_refptr<VideoFrame>& video_frame,
+      bool is_continuous);
+
+  const scoped_refptr<CastEnvironment> cast_environment_;
 
   // Subscribes to raw events.
   // Processes raw audio events to be sent over to the cast sender via RTCP.
   ReceiverRtcpEventSubscriber event_subscriber_;
 
-  scoped_ptr<Framer> framer_;
   const transport::VideoCodec codec_;
-  base::TimeDelta target_delay_delta_;
-  base::TimeDelta frame_delay_;
-  scoped_ptr<LocalRtpVideoFeedback> incoming_payload_feedback_;
-  scoped_ptr<Rtcp> rtcp_;
+  const base::TimeDelta target_delay_delta_;
+  const base::TimeDelta expected_frame_duration_;
+  Framer framer_;
+  scoped_ptr<VideoDecoder> video_decoder_;
+  Rtcp rtcp_;
   base::TimeDelta time_offset_;  // Sender-receiver offset estimation.
   int time_offset_counter_;
-  transport::TransportEncryptionHandler decryptor_;
-  std::list<VideoFrameEncodedCallback> queued_encoded_callbacks_;
   bool time_incoming_packet_updated_;
   base::TimeTicks time_incoming_packet_;
   uint32 incoming_rtp_timestamp_;
-  base::TimeTicks last_render_time_;
-  SetTargetDelayCallback target_delay_cb_;
+  transport::TransportEncryptionHandler decryptor_;
+
+  // Outstanding callbacks to run to deliver on client requests for frames.
+  std::list<VideoFrameEncodedCallback> frame_request_queue_;
+
+  // True while there's an outstanding task to re-invoke
+  // EmitAvailableEncodedFrames().
+  bool is_waiting_for_consecutive_frame_;
 
   // This mapping allows us to log kVideoAckSent as a frame event. In addition
   // it allows the event to be transmitted via RTCP.