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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.
// This is the base class for an object that send frames to a receiver.
// TODO(hclam): Refactor such that there is no separate AudioSender vs.
// VideoSender, and the functionality of both is rolled into this class.
#include "base/basictypes.h"
#include "base/memory/ref_counted.h"
#include "base/memory/weak_ptr.h"
#include "base/time/time.h"
#include "media/cast/cast_environment.h"
#include "media/cast/net/rtcp/rtcp.h"
#include "media/cast/sender/congestion_control.h"
namespace media {
namespace cast {
class FrameSender {
FrameSender(scoped_refptr<CastEnvironment> cast_environment,
bool is_audio,
CastTransportSender* const transport_sender,
base::TimeDelta rtcp_interval,
int rtp_timebase,
uint32 ssrc,
double max_frame_rate,
base::TimeDelta min_playout_delay,
base::TimeDelta max_playout_delay,
CongestionControl* congestion_control);
virtual ~FrameSender();
int rtp_timebase() const { return rtp_timebase_; }
// Calling this function is only valid if the receiver supports the
// "extra_playout_delay", rtp extension.
void SetTargetPlayoutDelay(base::TimeDelta new_target_playout_delay);
base::TimeDelta GetTargetPlayoutDelay() const {
return target_playout_delay_;
// Called by the encoder with the next EncodeFrame to send.
void SendEncodedFrame(int requested_bitrate_before_encode,
scoped_ptr<EncodedFrame> encoded_frame);
// Returns the number of frames in the encoder's backlog.
virtual int GetNumberOfFramesInEncoder() const = 0;
// Returns the duration of the data in the encoder's backlog plus the duration
// of sent, unacknowledged frames.
virtual base::TimeDelta GetInFlightMediaDuration() const = 0;
// Called when we get an ACK for a frame.
virtual void OnAck(uint32 frame_id) = 0;
// Schedule and execute periodic sending of RTCP report.
void ScheduleNextRtcpReport();
void SendRtcpReport(bool schedule_future_reports);
void OnMeasuredRoundTripTime(base::TimeDelta rtt);
const scoped_refptr<CastEnvironment> cast_environment_;
// Sends encoded frames over the configured transport (e.g., UDP). In
// Chromium, this could be a proxy that first sends the frames from a renderer
// process to the browser process over IPC, with the browser process being
// responsible for "packetizing" the frames and pushing packets into the
// network layer.
CastTransportSender* const transport_sender_;
const uint32 ssrc_;
// Schedule and execute periodic checks for re-sending packets. If no
// acknowledgements have been received for "too long," AudioSender will
// 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();
void ResendForKickstart();
// Protected for testability.
void OnReceivedCastFeedback(const RtcpCastMessage& cast_feedback);
// Returns true if too many frames would be in-flight by encoding and sending
// the next frame having the given |frame_duration|.
bool ShouldDropNextFrame(base::TimeDelta frame_duration) const;
// Record or retrieve a recent history of each frame's timestamps.
// Warning: If a frame ID too far in the past is requested, the getters will
// silently succeed but return incorrect values. Be sure to respect
// media::cast::kMaxUnackedFrames.
void RecordLatestFrameTimestamps(uint32 frame_id,
base::TimeTicks reference_time,
RtpTimestamp rtp_timestamp);
base::TimeTicks GetRecordedReferenceTime(uint32 frame_id) const;
RtpTimestamp GetRecordedRtpTimestamp(uint32 frame_id) const;
// Returns the number of frames that were sent but not yet acknowledged.
int GetUnacknowledgedFrameCount() const;
const base::TimeDelta rtcp_interval_;
// 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_;
base::TimeDelta min_playout_delay_;
base::TimeDelta max_playout_delay_;
// If true, we transmit the target playout delay to the receiver.
bool send_target_playout_delay_;
// Max encoded frames generated per second.
double max_frame_rate_;
// Counts how many RTCP reports are being "aggressively" sent (i.e., one per
// frame) at the start of the session. Once a threshold is reached, RTCP
// reports are instead sent at the configured interval + random drift.
int num_aggressive_rtcp_reports_sent_;
// This is "null" until the first frame is sent. Thereafter, this tracks the
// last time any frame was sent or re-sent.
base::TimeTicks last_send_time_;
// The ID of the last frame sent. Logic throughout FrameSender assumes this
// can safely wrap-around. This member is invalid until
// |!last_send_time_.is_null()|.
uint32 last_sent_frame_id_;
// The ID of the latest (not necessarily the last) frame that has been
// acknowledged. Logic throughout AudioSender assumes this can safely
// wrap-around. This member is invalid until |!last_send_time_.is_null()|.
uint32 latest_acked_frame_id_;
// Counts the number of duplicate ACK that are being received. When this
// number reaches a threshold, the sender will take this as a sign that the
// receiver hasn't yet received the first packet of the next frame. In this
// case, VideoSender will trigger a re-send of the next frame.
int duplicate_ack_counter_;
// This object controls how we change the bitrate to make sure the
// buffer doesn't overflow.
scoped_ptr<CongestionControl> congestion_control_;
// The most recently measured round trip time.
base::TimeDelta current_round_trip_time_;
// Returns the maximum media duration currently allowed in-flight. This
// fluctuates in response to the currently-measured network latency.
base::TimeDelta GetAllowedInFlightMediaDuration() const;
// RTP timestamp increment representing one second.
const int rtp_timebase_;
const bool is_audio_;
// Ring buffers to keep track of recent frame timestamps (both in terms of
// local reference time and RTP media time). These should only be accessed
// through the Record/GetXXX() methods.
base::TimeTicks frame_reference_times_[256];
RtpTimestamp frame_rtp_timestamps_[256];
// NOTE: Weak pointers must be invalidated before all other member variables.
base::WeakPtrFactory<FrameSender> weak_factory_;
} // namespace cast
} // namespace media