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+// 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.
+
+#ifndef MEDIA_CAST_RECEIVER_FRAME_RECEIVER_H_
+#define MEDIA_CAST_RECEIVER_FRAME_RECEIVER_H_
+
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "base/time/time.h"
+#include "media/cast/base/clock_drift_smoother.h"
+#include "media/cast/cast_config.h"
+#include "media/cast/cast_receiver.h"
+#include "media/cast/framer/framer.h"
+#include "media/cast/logging/logging_defines.h"
+#include "media/cast/rtcp/receiver_rtcp_event_subscriber.h"
+#include "media/cast/rtcp/rtcp.h"
+#include "media/cast/rtp_receiver/receiver_stats.h"
+#include "media/cast/rtp_receiver/rtp_parser/rtp_parser.h"
+#include "media/cast/rtp_receiver/rtp_receiver_defines.h"
+#include "media/cast/transport/utility/transport_encryption_handler.h"
+
+namespace media {
+namespace cast {
+
+class CastEnvironment;
+
+// FrameReceiver receives packets out-of-order while clients make requests for
+// complete frames in-order. (A frame consists of one or more packets.)
+//
+// FrameReceiver 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.
+//
+// Each request for a frame includes a callback which FrameReceiver guarantees
+// will be called at some point in the future unless the FrameReceiver is
+// destroyed. Clients should generally limit the number of outstanding requests
+// (perhaps to just one or two).
+//
+// This class is not thread safe. Should only be called from the Main cast
+// thread.
+class FrameReceiver : public RtpPayloadFeedback,
+ public base::SupportsWeakPtr<FrameReceiver> {
+ public:
+ FrameReceiver(const scoped_refptr<CastEnvironment>& cast_environment,
+ const FrameReceiverConfig& config,
+ EventMediaType event_media_type,
+ transport::PacedPacketSender* const packet_sender);
+
+ virtual ~FrameReceiver();
+
+ // Request an encoded frame.
+ //
+ // The given |callback| is guaranteed to be run at some point in the future,
+ // except for those requests still enqueued at destruction time.
+ void RequestEncodedFrame(const ReceiveEncodedFrameCallback& callback);
+
+ // Called to deliver another packet, possibly a duplicate, and possibly
+ // out-of-order. Returns true if the parsing of the packet succeeded.
+ bool ProcessPacket(scoped_ptr<Packet> packet);
+
+ // TODO(miu): This is the wrong place for this, but the (de)serialization
+ // implementation needs to be consolidated first.
+ static bool ParseSenderSsrc(const uint8* packet, size_t length, uint32* ssrc);
+
+ protected:
+ friend class FrameReceiverTest; // Invokes ProcessParsedPacket().
+
+ void ProcessParsedPacket(const RtpCastHeader& rtp_header,
+ const uint8* payload_data,
+ size_t payload_size);
+
+ // RtpPayloadFeedback implementation.
+ virtual void CastFeedback(const RtcpCastMessage& cast_message) OVERRIDE;
+
+ private:
+ // 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();
+
+ // Computes the playout time for a frame with the given |rtp_timestamp|.
+ // Because lip-sync info is refreshed regularly, calling this method with the
+ // same argument may return different results.
+ base::TimeTicks GetPlayoutTime(uint32 rtp_timestamp) const;
+
+ // Schedule timing for the next cast message.
+ void ScheduleNextCastMessage();
+
+ // Schedule timing for the next RTCP report.
+ void ScheduleNextRtcpReport();
+
+ // Actually send the next cast message.
+ void SendNextCastMessage();
+
+ // Actually send the next RTCP report.
+ void SendNextRtcpReport();
+
+ const scoped_refptr<CastEnvironment> cast_environment_;
+
+ // Deserializes a packet into a RtpHeader + payload bytes.
+ RtpParser packet_parser_;
+
+ // Accumulates packet statistics, including packet loss, counts, and jitter.
+ ReceiverStats stats_;
+
+ // Partitions logged events by the type of media passing through.
+ EventMediaType event_media_type_;
+
+ // Subscribes to raw events.
+ // Processes raw events to be sent over to the cast sender via RTCP.
+ ReceiverRtcpEventSubscriber event_subscriber_;
+
+ // RTP timebase: The number of RTP units advanced per one second.
+ const int rtp_timebase_;
+
+ // 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.).
+ const base::TimeDelta target_playout_delay_;
+
+ // Hack: This is used in logic that determines whether to skip frames.
+ // TODO(miu): Revisit this. Logic needs to also account for expected decode
+ // time.
+ const base::TimeDelta expected_frame_duration_;
+
+ // Set to false initially, then set to true after scheduling the periodic
+ // sending of reports back to the sender. Reports are first scheduled just
+ // after receiving a first packet (since the first packet identifies the
+ // sender for the remainder of the session).
+ bool reports_are_scheduled_;
+
+ // Assembles packets into frames, providing this receiver with complete,
+ // decodable EncodedFrames.
+ Framer framer_;
+
+ // Manages sending/receiving of RTCP packets, including sender/receiver
+ // reports.
+ Rtcp rtcp_;
+
+ // Decrypts encrypted frames.
+ transport::TransportEncryptionHandler decryptor_;
+
+ // Outstanding callbacks to run to deliver on client requests for frames.
+ std::list<ReceiveEncodedFrameCallback> 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 FRAME_ACK_SENT as a frame event. In addition
+ // it allows the event to be transmitted via RTCP.
+ RtpTimestamp frame_id_to_rtp_timestamp_[256];
+
+ // Lip-sync values used to compute the playout time of each frame from its RTP
+ // timestamp. These are updated each time the first packet of a frame is
+ // received.
+ RtpTimestamp lip_sync_rtp_timestamp_;
+ base::TimeTicks lip_sync_reference_time_;
+ ClockDriftSmoother lip_sync_drift_;
+
+ // NOTE: Weak pointers must be invalidated before all other member variables.
+ base::WeakPtrFactory<FrameReceiver> weak_factory_;
+
+ DISALLOW_COPY_AND_ASSIGN(FrameReceiver);
+};
+
+} // namespace cast
+} // namespace media
+
+#endif // MEDIA_CAST_RECEIVER_FRAME_RECEIVER_H_