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/*
* Copyright (c) 2019 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef MODULES_PACING_PACING_CONTROLLER_H_
#define MODULES_PACING_PACING_CONTROLLER_H_
#include <stddef.h>
#include <stdint.h>
#include <array>
#include <memory>
#include <optional>
#include <vector>
#include "api/array_view.h"
#include "api/field_trials_view.h"
#include "api/rtp_packet_sender.h"
#include "api/transport/network_types.h"
#include "api/units/data_rate.h"
#include "api/units/data_size.h"
#include "api/units/time_delta.h"
#include "api/units/timestamp.h"
#include "modules/pacing/bitrate_prober.h"
#include "modules/pacing/prioritized_packet_queue.h"
#include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
#include "modules/rtp_rtcp/source/rtp_packet_to_send.h"
#include "system_wrappers/include/clock.h"
namespace webrtc {
// This class implements a leaky-bucket packet pacing algorithm. It handles the
// logic of determining which packets to send when, but the actual timing of
// the processing is done externally (e.g. RtpPacketPacer). Furthermore, the
// forwarding of packets when they are ready to be sent is also handled
// externally, via the PacingController::PacketSender interface.
class PacingController {
public:
class PacketSender {
public:
virtual ~PacketSender() = default;
virtual void SendPacket(std::unique_ptr<RtpPacketToSend> packet,
const PacedPacketInfo& cluster_info) = 0;
// Should be called after each call to SendPacket().
virtual std::vector<std::unique_ptr<RtpPacketToSend>> FetchFec() = 0;
virtual std::vector<std::unique_ptr<RtpPacketToSend>> GeneratePadding(
DataSize size) = 0;
// TODO(bugs.webrtc.org/1439830): Make pure virtual once subclasses adapt.
virtual void OnBatchComplete() {}
// TODO(bugs.webrtc.org/11340): Make pure virtual once downstream projects
// have been updated.
virtual void OnAbortedRetransmissions(
uint32_t ssrc,
rtc::ArrayView<const uint16_t> sequence_numbers) {}
virtual std::optional<uint32_t> GetRtxSsrcForMedia(uint32_t ssrc) const {
return std::nullopt;
}
};
// If no media or paused, wake up at least every `kPausedProcessIntervalMs` in
// order to send a keep-alive packet so we don't get stuck in a bad state due
// to lack of feedback.
static const TimeDelta kPausedProcessInterval;
// The default minimum time that should elapse calls to `ProcessPackets()`.
static const TimeDelta kMinSleepTime;
// When padding should be generated, add packets to the buffer with a size
// corresponding to this duration times the current padding rate.
static const TimeDelta kTargetPaddingDuration;
// The maximum time that the pacer can use when "replaying" passed time where
// padding should have been generated.
static const TimeDelta kMaxPaddingReplayDuration;
// Allow probes to be processed slightly ahead of inteded send time. Currently
// set to 1ms as this is intended to allow times be rounded down to the
// nearest millisecond.
static const TimeDelta kMaxEarlyProbeProcessing;
// Max total size of packets expected to be sent in a burst in order to not
// risk loosing packets due to too small send socket buffers. It upper limits
// the send burst interval.
// Ex: max send burst interval = 63Kb / 10Mbit/s = 50ms.
static constexpr DataSize kMaxBurstSize = DataSize::Bytes(63 * 1000);
// Configuration default values.
static constexpr TimeDelta kDefaultBurstInterval = TimeDelta::Millis(40);
static constexpr TimeDelta kMaxExpectedQueueLength = TimeDelta::Millis(2000);
struct Configuration {
// If the pacer queue grows longer than the configured max queue limit,
// pacer sends at the minimum rate needed to keep the max queue limit and
// ignore the current bandwidth estimate.
bool drain_large_queues = true;
// Expected max pacer delay. If ExpectedQueueTime() is higher than
// this value, the packet producers should wait (eg drop frames rather than
// encoding them). Bitrate sent may temporarily exceed target set by
// SetPacingRates() so that this limit will be upheld if
// `drain_large_queues` is set.
TimeDelta queue_time_limit = kMaxExpectedQueueLength;
// If the first packet of a keyframe is enqueued on a RTP stream, pacer
// skips forward to that packet and drops other enqueued packets on that
// stream, unless a keyframe is already being paced.
bool keyframe_flushing = false;
// Audio retransmission is prioritized before video retransmission packets.
bool prioritize_audio_retransmission = false;
// Configure separate timeouts per priority. After a timeout, a packet of
// that sort will not be paced and instead dropped.
// Note: to set TTL on audio retransmission,
// `prioritize_audio_retransmission` must be true.
PacketQueueTTL packet_queue_ttl;
// The pacer is allowed to send enqueued packets in bursts and can build up
// a packet "debt" that correspond to approximately the send rate during the
// burst interval.
TimeDelta send_burst_interval = kDefaultBurstInterval;
};
static Configuration DefaultConfiguration() { return Configuration{}; }
PacingController(Clock* clock,
PacketSender* packet_sender,
const FieldTrialsView& field_trials,
Configuration configuration = DefaultConfiguration());
~PacingController();
// Adds the packet to the queue and calls PacketRouter::SendPacket() when
// it's time to send.
void EnqueuePacket(std::unique_ptr<RtpPacketToSend> packet);
void CreateProbeClusters(
rtc::ArrayView<const ProbeClusterConfig> probe_cluster_configs);
void Pause(); // Temporarily pause all sending.
void Resume(); // Resume sending packets.
bool IsPaused() const;
void SetCongested(bool congested);
// Sets the pacing rates. Must be called once before packets can be sent.
void SetPacingRates(DataRate pacing_rate, DataRate padding_rate);
DataRate pacing_rate() const { return adjusted_media_rate_; }
// Currently audio traffic is not accounted by pacer and passed through.
// With the introduction of audio BWE audio traffic will be accounted for
// the pacer budget calculation. The audio traffic still will be injected
// at high priority.
void SetAccountForAudioPackets(bool account_for_audio);
void SetIncludeOverhead();
void SetTransportOverhead(DataSize overhead_per_packet);
// The pacer is allowed to send enqued packets in bursts and can build up a
// packet "debt" that correspond to approximately the send rate during
// 'burst_interval'.
void SetSendBurstInterval(TimeDelta burst_interval);
// A probe may be sent without first waing for a media packet.
void SetAllowProbeWithoutMediaPacket(bool allow);
// Returns the time when the oldest packet was queued.
Timestamp OldestPacketEnqueueTime() const;
// Number of packets in the pacer queue.
size_t QueueSizePackets() const;
// Number of packets in the pacer queue per media type (RtpPacketMediaType
// values are used as lookup index).
const std::array<int, kNumMediaTypes>& SizeInPacketsPerRtpPacketMediaType()
const;
// Totals size of packets in the pacer queue.
DataSize QueueSizeData() const;
// Current buffer level, i.e. max of media and padding debt.
DataSize CurrentBufferLevel() const;
// Returns the time when the first packet was sent.
std::optional<Timestamp> FirstSentPacketTime() const;
// Returns the number of milliseconds it will take to send the current
// packets in the queue, given the current size and bitrate, ignoring prio.
TimeDelta ExpectedQueueTime() const;
void SetQueueTimeLimit(TimeDelta limit);
// Enable bitrate probing. Enabled by default, mostly here to simplify
// testing. Must be called before any packets are being sent to have an
// effect.
void SetProbingEnabled(bool enabled);
// Returns the next time we expect ProcessPackets() to be called.
Timestamp NextSendTime() const;
// Check queue of pending packets and send them or padding packets, if budget
// is available.
void ProcessPackets();
bool IsProbing() const;
// Note: Intended for debugging purposes only, will be removed.
// Sets the number of iterations of the main loop in `ProcessPackets()` that
// is considered erroneous to exceed.
void SetCircuitBreakerThreshold(int num_iterations);
// Remove any pending packets matching this SSRC from the packet queue.
void RemovePacketsForSsrc(uint32_t ssrc);
private:
TimeDelta UpdateTimeAndGetElapsed(Timestamp now);
bool ShouldSendKeepalive(Timestamp now) const;
// Updates the number of bytes that can be sent for the next time interval.
void UpdateBudgetWithElapsedTime(TimeDelta delta);
void UpdateBudgetWithSentData(DataSize size);
void UpdatePaddingBudgetWithSentData(DataSize size);
DataSize PaddingToAdd(DataSize recommended_probe_size,
DataSize data_sent) const;
std::unique_ptr<RtpPacketToSend> GetPendingPacket(
const PacedPacketInfo& pacing_info,
Timestamp target_send_time,
Timestamp now);
void OnPacketSent(RtpPacketMediaType packet_type,
DataSize packet_size,
Timestamp send_time);
void MaybeUpdateMediaRateDueToLongQueue(Timestamp now);
Timestamp CurrentTime() const;
// Helper methods for packet that may not be paced. Returns a finite Timestamp
// if a packet type is configured to not be paced and the packet queue has at
// least one packet of that type. Otherwise returns
// Timestamp::MinusInfinity().
Timestamp NextUnpacedSendTime() const;
Clock* const clock_;
PacketSender* const packet_sender_;
const FieldTrialsView& field_trials_;
const bool drain_large_queues_;
const bool send_padding_if_silent_;
const bool pace_audio_;
const bool ignore_transport_overhead_;
const bool fast_retransmissions_;
const bool keyframe_flushing_;
DataRate max_rate = DataRate::BitsPerSec(100'000'000);
DataSize transport_overhead_per_packet_;
TimeDelta send_burst_interval_;
// TODO(webrtc:9716): Remove this when we are certain clocks are monotonic.
// The last millisecond timestamp returned by `clock_`.
mutable Timestamp last_timestamp_;
bool paused_;
// Amount of outstanding data for media and padding.
DataSize media_debt_;
DataSize padding_debt_;
// The target pacing rate, signaled via SetPacingRates().
DataRate pacing_rate_;
// The media send rate, which might adjusted from pacing_rate_, e.g. if the
// pacing queue is growing too long.
DataRate adjusted_media_rate_;
// The padding target rate. We aim to fill up to this rate with padding what
// is not already used by media.
DataRate padding_rate_;
BitrateProber prober_;
bool probing_send_failure_;
Timestamp last_process_time_;
Timestamp last_send_time_;
std::optional<Timestamp> first_sent_packet_time_;
bool seen_first_packet_;
PrioritizedPacketQueue packet_queue_;
bool congested_;
TimeDelta queue_time_limit_;
bool account_for_audio_;
bool include_overhead_;
int circuit_breaker_threshold_;
};
} // namespace webrtc
#endif // MODULES_PACING_PACING_CONTROLLER_H_