blob: 16bceb655c36b3e51a73672063c25f6fa7ac4955 [file] [log] [blame]
// 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.
#include <stdint.h>
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/memory/weak_ptr.h"
#include "base/time/time.h"
#include "media/cast/cast_config.h"
#include "media/cast/cast_environment.h"
#include "media/cast/net/cast_transport.h"
#include "media/cast/net/rtcp/rtcp_defines.h"
#include "media/cast/sender/congestion_control.h"
namespace media {
namespace cast {
struct SenderEncodedFrame;
class FrameSender {
FrameSender(scoped_refptr<CastEnvironment> cast_environment,
CastTransport* const transport_sender,
const FrameSenderConfig& config,
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,
std::unique_ptr<SenderEncodedFrame> 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;
// One or more frames were canceled.
virtual void OnCancelSendingFrames();
class RtcpClient : public RtcpObserver {
explicit RtcpClient(base::WeakPtr<FrameSender> frame_sender);
~RtcpClient() override;
void OnReceivedCastMessage(const RtcpCastMessage& cast_message) override;
void OnReceivedRtt(base::TimeDelta round_trip_time) override;
void OnReceivedPli() override;
const base::WeakPtr<FrameSender> frame_sender_;
// Schedule and execute periodic sending of RTCP report.
void ScheduleNextRtcpReport();
void SendRtcpReport(bool schedule_future_reports);
// Protected for testability.
void OnReceivedCastFeedback(const RtcpCastMessage& cast_feedback);
// Called when a Pli message is received.
void OnReceivedPli();
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.
CastTransport* const transport_sender_;
const uint32_t ssrc_;
// Schedule and execute periodic checks for re-sending packets. If no
// acknowledgements have been received for "too long," FrameSender 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();
// 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(FrameId frame_id,
base::TimeTicks reference_time,
RtpTimeTicks rtp_timestamp);
base::TimeTicks GetRecordedReferenceTime(FrameId frame_id) const;
RtpTimeTicks GetRecordedRtpTimestamp(FrameId frame_id) const;
// Returns the number of frames that were sent but not yet acknowledged.
int GetUnacknowledgedFrameCount() const;
// Playout delay represents 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 should be 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.).
// The |target_playout delay_| is the current delay that is adaptively
// adjusted based on feedback from video capture engine and the congestion
// control. In case of interactive content, the target is adjusted to start
// at |min_playout_delay_| and in case of animated content, it starts out at
// |animated_playout_delay_| and then adaptively adjust based on feedback
// from congestion control.
base::TimeDelta target_playout_delay_;
const base::TimeDelta min_playout_delay_;
const base::TimeDelta max_playout_delay_;
// Starting playout delay for animated content.
const base::TimeDelta animated_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. This member is invalid until
// |!last_send_time_.is_null()|.
FrameId last_sent_frame_id_;
// The ID of the latest (not necessarily the last) frame that has been
// acknowledged. This member is invalid until |!last_send_time_.is_null()|.
FrameId 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, FrameSender 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.
std::unique_ptr<CongestionControl> congestion_control_;
// The most recently measured round trip time.
base::TimeDelta current_round_trip_time_;
// This flag is set true when a Pli message is received. It is cleared once
// the FrameSender scheduled an encoded key frame to be sent.
bool picture_lost_at_receiver_;
// 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_;
// This is the maximum delay that the sender should get ack from receiver.
// Otherwise, sender will call ResendForKickstart().
base::TimeDelta max_ack_delay_;
// 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. The index into this ring
// buffer is the lower 8 bits of the FrameId.
base::TimeTicks frame_reference_times_[256];
RtpTimeTicks frame_rtp_timestamps_[256];
// NOTE: Weak pointers must be invalidated before all other member variables.
base::WeakPtrFactory<FrameSender> weak_factory_{this};
} // namespace cast
} // namespace media