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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.
#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/cast_config.h"
#include "media/cast/cast_receiver.h"
#include "media/cast/common/clock_drift_smoother.h"
#include "media/cast/common/transport_encryption_handler.h"
#include "media/cast/logging/logging_defines.h"
#include "media/cast/net/rtcp/receiver_rtcp_event_subscriber.h"
#include "media/cast/net/rtcp/rtcp.h"
#include "media/cast/net/rtp/framer.h"
#include "media/cast/net/rtp/receiver_stats.h"
#include "media/cast/net/rtp/rtp_parser.h"
#include "media/cast/net/rtp/rtp_receiver_defines.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> {
FrameReceiver(const scoped_refptr<CastEnvironment>& cast_environment,
const FrameReceiverConfig& config,
EventMediaType event_media_type,
CastTransportSender* const transport);
~FrameReceiver() override;
// 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);
friend class FrameReceiverTest; // Invokes ProcessParsedPacket().
void ProcessParsedPacket(const RtpCastHeader& rtp_header,
const uint8* payload_data,
size_t payload_size);
// RtpPayloadFeedback implementation.
void CastFeedback(const RtcpCastMessage& cast_message) override;
// 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();
// Helper that runs |callback|, passing ownership of |encoded_frame| to it.
// This method is used by EmitAvailableEncodedFrames() to return to the event
// loop, but make sure that FrameReceiver is still alive before the callback
// is run.
void EmitOneFrame(const ReceiveEncodedFrameCallback& callback,
scoped_ptr<EncodedFrame> encoded_frame) const;
// 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(const EncodedFrame& frame) 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_;
// Transport used to send data back.
CastTransportSender* const transport_;
// 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.).
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.
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_;
// Time interval for sending a RTCP report.
const base::TimeDelta rtcp_interval_;
// NOTE: Weak pointers must be invalidated before all other member variables.
base::WeakPtrFactory<FrameReceiver> weak_factory_;
} // namespace cast
} // namespace media