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/*
* Copyright (c) 2012 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.
*/
#include "modules/pacing/paced_sender.h"
#include <algorithm>
#include <map>
#include <queue>
#include <set>
#include <vector>
#include "modules/include/module_common_types.h"
#include "modules/pacing/alr_detector.h"
#include "modules/pacing/bitrate_prober.h"
#include "modules/pacing/interval_budget.h"
#include "modules/utility/include/process_thread.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
#include "system_wrappers/include/clock.h"
#include "system_wrappers/include/field_trial.h"
namespace {
// Time limit in milliseconds between packet bursts.
const int64_t kMinPacketLimitMs = 5;
const int64_t kPausedPacketIntervalMs = 500;
// Upper cap on process interval, in case process has not been called in a long
// time.
const int64_t kMaxIntervalTimeMs = 30;
} // namespace
// TODO(sprang): Move at least PacketQueue out to separate files, so that we can
// more easily test them.
namespace webrtc {
namespace paced_sender {
struct Packet {
Packet(RtpPacketSender::Priority priority,
uint32_t ssrc,
uint16_t seq_number,
int64_t capture_time_ms,
int64_t enqueue_time_ms,
size_t length_in_bytes,
bool retransmission,
uint64_t enqueue_order)
: priority(priority),
ssrc(ssrc),
sequence_number(seq_number),
capture_time_ms(capture_time_ms),
enqueue_time_ms(enqueue_time_ms),
sum_paused_ms(0),
bytes(length_in_bytes),
retransmission(retransmission),
enqueue_order(enqueue_order) {}
RtpPacketSender::Priority priority;
uint32_t ssrc;
uint16_t sequence_number;
int64_t capture_time_ms; // Absolute time of frame capture.
int64_t enqueue_time_ms; // Absolute time of pacer queue entry.
int64_t sum_paused_ms; // Sum of time spent in queue while pacer is paused.
size_t bytes;
bool retransmission;
uint64_t enqueue_order;
std::list<Packet>::iterator this_it;
};
// Used by priority queue to sort packets.
struct Comparator {
bool operator()(const Packet* first, const Packet* second) {
// Highest prio = 0.
if (first->priority != second->priority)
return first->priority > second->priority;
// Retransmissions go first.
if (second->retransmission != first->retransmission)
return second->retransmission;
// Older frames have higher prio.
if (first->capture_time_ms != second->capture_time_ms)
return first->capture_time_ms > second->capture_time_ms;
return first->enqueue_order > second->enqueue_order;
}
};
// Class encapsulating a priority queue with some extensions.
class PacketQueue {
public:
explicit PacketQueue(const Clock* clock)
: bytes_(0),
clock_(clock),
queue_time_sum_(0),
time_last_updated_(clock_->TimeInMilliseconds()),
paused_(false) {}
virtual ~PacketQueue() {}
void Push(const Packet& packet) {
if (!AddToDupeSet(packet))
return;
UpdateQueueTime(packet.enqueue_time_ms);
// Store packet in list, use pointers in priority queue for cheaper moves.
// Packets have a handle to its own iterator in the list, for easy removal
// when popping from queue.
packet_list_.push_front(packet);
std::list<Packet>::iterator it = packet_list_.begin();
it->this_it = it; // Handle for direct removal from list.
prio_queue_.push(&(*it)); // Pointer into list.
bytes_ += packet.bytes;
}
const Packet& BeginPop() {
const Packet& packet = *prio_queue_.top();
prio_queue_.pop();
return packet;
}
void CancelPop(const Packet& packet) { prio_queue_.push(&(*packet.this_it)); }
void FinalizePop(const Packet& packet) {
RemoveFromDupeSet(packet);
bytes_ -= packet.bytes;
int64_t packet_queue_time_ms = time_last_updated_ - packet.enqueue_time_ms;
RTC_DCHECK_LE(packet.sum_paused_ms, packet_queue_time_ms);
packet_queue_time_ms -= packet.sum_paused_ms;
RTC_DCHECK_LE(packet_queue_time_ms, queue_time_sum_);
queue_time_sum_ -= packet_queue_time_ms;
packet_list_.erase(packet.this_it);
RTC_DCHECK_EQ(packet_list_.size(), prio_queue_.size());
if (packet_list_.empty())
RTC_DCHECK_EQ(0, queue_time_sum_);
}
bool Empty() const { return prio_queue_.empty(); }
size_t SizeInPackets() const { return prio_queue_.size(); }
uint64_t SizeInBytes() const { return bytes_; }
int64_t OldestEnqueueTimeMs() const {
auto it = packet_list_.rbegin();
if (it == packet_list_.rend())
return 0;
return it->enqueue_time_ms;
}
void UpdateQueueTime(int64_t timestamp_ms) {
RTC_DCHECK_GE(timestamp_ms, time_last_updated_);
if (timestamp_ms == time_last_updated_)
return;
int64_t delta_ms = timestamp_ms - time_last_updated_;
if (paused_) {
// Increase per-packet accumulators of time spent in queue while paused,
// so that we can disregard that when subtracting main accumulator when
// popping packet from the queue.
for (auto& it : packet_list_) {
it.sum_paused_ms += delta_ms;
}
} else {
// Use packet packet_list_.size() not prio_queue_.size() here, as there
// might be an outstanding element popped from prio_queue_ currently in
// the SendPacket() call, while packet_list_ will always be correct.
queue_time_sum_ += delta_ms * packet_list_.size();
}
time_last_updated_ = timestamp_ms;
}
void SetPauseState(bool paused, int64_t timestamp_ms) {
if (paused_ == paused)
return;
UpdateQueueTime(timestamp_ms);
paused_ = paused;
}
int64_t AverageQueueTimeMs() const {
if (prio_queue_.empty())
return 0;
return queue_time_sum_ / packet_list_.size();
}
private:
// Try to add a packet to the set of ssrc/seqno identifiers currently in the
// queue. Return true if inserted, false if this is a duplicate.
bool AddToDupeSet(const Packet& packet) {
SsrcSeqNoMap::iterator it = dupe_map_.find(packet.ssrc);
if (it == dupe_map_.end()) {
// First for this ssrc, just insert.
dupe_map_[packet.ssrc].insert(packet.sequence_number);
return true;
}
// Insert returns a pair, where second is a bool set to true if new element.
return it->second.insert(packet.sequence_number).second;
}
void RemoveFromDupeSet(const Packet& packet) {
SsrcSeqNoMap::iterator it = dupe_map_.find(packet.ssrc);
RTC_DCHECK(it != dupe_map_.end());
it->second.erase(packet.sequence_number);
if (it->second.empty()) {
dupe_map_.erase(it);
}
}
// List of packets, in the order the were enqueued. Since dequeueing may
// occur out of order, use list instead of vector.
std::list<Packet> packet_list_;
// Priority queue of the packets, sorted according to Comparator.
// Use pointers into list, to avoid moving whole struct within heap.
std::priority_queue<Packet*, std::vector<Packet*>, Comparator> prio_queue_;
// Total number of bytes in the queue.
uint64_t bytes_;
// Map<ssrc, std::set<seq_no> >, for checking duplicates.
typedef std::map<uint32_t, std::set<uint16_t> > SsrcSeqNoMap;
SsrcSeqNoMap dupe_map_;
const Clock* const clock_;
int64_t queue_time_sum_;
int64_t time_last_updated_;
bool paused_;
};
} // namespace paced_sender
const int64_t PacedSender::kMaxQueueLengthMs = 2000;
const float PacedSender::kDefaultPaceMultiplier = 2.5f;
PacedSender::PacedSender(const Clock* clock,
PacketSender* packet_sender,
RtcEventLog* event_log)
: clock_(clock),
packet_sender_(packet_sender),
alr_detector_(new AlrDetector()),
paused_(false),
media_budget_(new IntervalBudget(0)),
padding_budget_(new IntervalBudget(0)),
prober_(new BitrateProber(event_log)),
probing_send_failure_(false),
estimated_bitrate_bps_(0),
min_send_bitrate_kbps_(0u),
max_padding_bitrate_kbps_(0u),
pacing_bitrate_kbps_(0),
time_last_update_us_(clock->TimeInMicroseconds()),
first_sent_packet_ms_(-1),
packets_(new paced_sender::PacketQueue(clock)),
packet_counter_(0),
pacing_factor_(kDefaultPaceMultiplier),
queue_time_limit(kMaxQueueLengthMs) {
UpdateBudgetWithElapsedTime(kMinPacketLimitMs);
}
PacedSender::~PacedSender() {}
void PacedSender::CreateProbeCluster(int bitrate_bps) {
rtc::CritScope cs(&critsect_);
prober_->CreateProbeCluster(bitrate_bps, clock_->TimeInMilliseconds());
}
void PacedSender::Pause() {
{
rtc::CritScope cs(&critsect_);
if (!paused_)
LOG(LS_INFO) << "PacedSender paused.";
paused_ = true;
packets_->SetPauseState(true, clock_->TimeInMilliseconds());
}
// Tell the process thread to call our TimeUntilNextProcess() method to get
// a new (longer) estimate for when to call Process().
if (process_thread_)
process_thread_->WakeUp(this);
}
void PacedSender::Resume() {
{
rtc::CritScope cs(&critsect_);
if (paused_)
LOG(LS_INFO) << "PacedSender resumed.";
paused_ = false;
packets_->SetPauseState(false, clock_->TimeInMilliseconds());
}
// Tell the process thread to call our TimeUntilNextProcess() method to
// refresh the estimate for when to call Process().
if (process_thread_)
process_thread_->WakeUp(this);
}
void PacedSender::SetProbingEnabled(bool enabled) {
RTC_CHECK_EQ(0, packet_counter_);
rtc::CritScope cs(&critsect_);
prober_->SetEnabled(enabled);
}
void PacedSender::SetEstimatedBitrate(uint32_t bitrate_bps) {
if (bitrate_bps == 0)
LOG(LS_ERROR) << "PacedSender is not designed to handle 0 bitrate.";
rtc::CritScope cs(&critsect_);
estimated_bitrate_bps_ = bitrate_bps;
padding_budget_->set_target_rate_kbps(
std::min(estimated_bitrate_bps_ / 1000, max_padding_bitrate_kbps_));
pacing_bitrate_kbps_ =
std::max(min_send_bitrate_kbps_, estimated_bitrate_bps_ / 1000) *
pacing_factor_;
alr_detector_->SetEstimatedBitrate(bitrate_bps);
}
void PacedSender::SetSendBitrateLimits(int min_send_bitrate_bps,
int padding_bitrate) {
rtc::CritScope cs(&critsect_);
min_send_bitrate_kbps_ = min_send_bitrate_bps / 1000;
pacing_bitrate_kbps_ =
std::max(min_send_bitrate_kbps_, estimated_bitrate_bps_ / 1000) *
pacing_factor_;
max_padding_bitrate_kbps_ = padding_bitrate / 1000;
padding_budget_->set_target_rate_kbps(
std::min(estimated_bitrate_bps_ / 1000, max_padding_bitrate_kbps_));
}
void PacedSender::InsertPacket(RtpPacketSender::Priority priority,
uint32_t ssrc,
uint16_t sequence_number,
int64_t capture_time_ms,
size_t bytes,
bool retransmission) {
rtc::CritScope cs(&critsect_);
RTC_DCHECK(estimated_bitrate_bps_ > 0)
<< "SetEstimatedBitrate must be called before InsertPacket.";
int64_t now_ms = clock_->TimeInMilliseconds();
prober_->OnIncomingPacket(bytes);
if (capture_time_ms < 0)
capture_time_ms = now_ms;
packets_->Push(paced_sender::Packet(priority, ssrc, sequence_number,
capture_time_ms, now_ms, bytes,
retransmission, packet_counter_++));
}
int64_t PacedSender::ExpectedQueueTimeMs() const {
rtc::CritScope cs(&critsect_);
RTC_DCHECK_GT(pacing_bitrate_kbps_, 0);
return static_cast<int64_t>(packets_->SizeInBytes() * 8 /
pacing_bitrate_kbps_);
}
rtc::Optional<int64_t> PacedSender::GetApplicationLimitedRegionStartTime()
const {
rtc::CritScope cs(&critsect_);
return alr_detector_->GetApplicationLimitedRegionStartTime();
}
size_t PacedSender::QueueSizePackets() const {
rtc::CritScope cs(&critsect_);
return packets_->SizeInPackets();
}
int64_t PacedSender::FirstSentPacketTimeMs() const {
rtc::CritScope cs(&critsect_);
return first_sent_packet_ms_;
}
int64_t PacedSender::QueueInMs() const {
rtc::CritScope cs(&critsect_);
int64_t oldest_packet = packets_->OldestEnqueueTimeMs();
if (oldest_packet == 0)
return 0;
return clock_->TimeInMilliseconds() - oldest_packet;
}
int64_t PacedSender::AverageQueueTimeMs() {
rtc::CritScope cs(&critsect_);
packets_->UpdateQueueTime(clock_->TimeInMilliseconds());
return packets_->AverageQueueTimeMs();
}
int64_t PacedSender::TimeUntilNextProcess() {
rtc::CritScope cs(&critsect_);
int64_t elapsed_time_us = clock_->TimeInMicroseconds() - time_last_update_us_;
int64_t elapsed_time_ms = (elapsed_time_us + 500) / 1000;
// When paused we wake up every 500 ms to send a padding packet to ensure
// we won't get stuck in the paused state due to no feedback being received.
if (paused_)
return std::max<int64_t>(kPausedPacketIntervalMs - elapsed_time_ms, 0);
if (prober_->IsProbing()) {
int64_t ret = prober_->TimeUntilNextProbe(clock_->TimeInMilliseconds());
if (ret > 0 || (ret == 0 && !probing_send_failure_))
return ret;
}
return std::max<int64_t>(kMinPacketLimitMs - elapsed_time_ms, 0);
}
void PacedSender::Process() {
int64_t now_us = clock_->TimeInMicroseconds();
rtc::CritScope cs(&critsect_);
int64_t elapsed_time_ms = std::min(
kMaxIntervalTimeMs, (now_us - time_last_update_us_ + 500) / 1000);
int target_bitrate_kbps = pacing_bitrate_kbps_;
if (paused_) {
PacedPacketInfo pacing_info;
time_last_update_us_ = now_us;
// We can not send padding unless a normal packet has first been sent. If we
// do, timestamps get messed up.
if (packet_counter_ == 0)
return;
size_t bytes_sent = SendPadding(1, pacing_info);
alr_detector_->OnBytesSent(bytes_sent, elapsed_time_ms);
return;
}
if (elapsed_time_ms > 0) {
size_t queue_size_bytes = packets_->SizeInBytes();
if (queue_size_bytes > 0) {
// Assuming equal size packets and input/output rate, the average packet
// has avg_time_left_ms left to get queue_size_bytes out of the queue, if
// time constraint shall be met. Determine bitrate needed for that.
packets_->UpdateQueueTime(clock_->TimeInMilliseconds());
int64_t avg_time_left_ms = std::max<int64_t>(
1, queue_time_limit - packets_->AverageQueueTimeMs());
int min_bitrate_needed_kbps =
static_cast<int>(queue_size_bytes * 8 / avg_time_left_ms);
if (min_bitrate_needed_kbps > target_bitrate_kbps)
target_bitrate_kbps = min_bitrate_needed_kbps;
}
media_budget_->set_target_rate_kbps(target_bitrate_kbps);
UpdateBudgetWithElapsedTime(elapsed_time_ms);
}
time_last_update_us_ = now_us;
bool is_probing = prober_->IsProbing();
PacedPacketInfo pacing_info;
size_t bytes_sent = 0;
size_t recommended_probe_size = 0;
if (is_probing) {
pacing_info = prober_->CurrentCluster();
recommended_probe_size = prober_->RecommendedMinProbeSize();
}
while (!packets_->Empty()) {
// Since we need to release the lock in order to send, we first pop the
// element from the priority queue but keep it in storage, so that we can
// reinsert it if send fails.
const paced_sender::Packet& packet = packets_->BeginPop();
if (SendPacket(packet, pacing_info)) {
// Send succeeded, remove it from the queue.
if (first_sent_packet_ms_ == -1)
first_sent_packet_ms_ = clock_->TimeInMilliseconds();
bytes_sent += packet.bytes;
packets_->FinalizePop(packet);
if (is_probing && bytes_sent > recommended_probe_size)
break;
} else {
// Send failed, put it back into the queue.
packets_->CancelPop(packet);
break;
}
}
if (packets_->Empty()) {
// We can not send padding unless a normal packet has first been sent. If we
// do, timestamps get messed up.
if (packet_counter_ > 0) {
int padding_needed =
static_cast<int>(is_probing ? (recommended_probe_size - bytes_sent)
: padding_budget_->bytes_remaining());
if (padding_needed > 0)
bytes_sent += SendPadding(padding_needed, pacing_info);
}
}
if (is_probing) {
probing_send_failure_ = bytes_sent == 0;
if (!probing_send_failure_)
prober_->ProbeSent(clock_->TimeInMilliseconds(), bytes_sent);
}
alr_detector_->OnBytesSent(bytes_sent, elapsed_time_ms);
}
void PacedSender::ProcessThreadAttached(ProcessThread* process_thread) {
LOG(LS_INFO) << "ProcessThreadAttached 0x" << std::hex << process_thread;
process_thread_ = process_thread;
}
bool PacedSender::SendPacket(const paced_sender::Packet& packet,
const PacedPacketInfo& pacing_info) {
RTC_DCHECK(!paused_);
if (media_budget_->bytes_remaining() == 0 &&
pacing_info.probe_cluster_id == PacedPacketInfo::kNotAProbe) {
return false;
}
critsect_.Leave();
const bool success = packet_sender_->TimeToSendPacket(
packet.ssrc, packet.sequence_number, packet.capture_time_ms,
packet.retransmission, pacing_info);
critsect_.Enter();
if (success) {
// TODO(holmer): High priority packets should only be accounted for if we
// are allocating bandwidth for audio.
if (packet.priority != kHighPriority) {
// Update media bytes sent.
// TODO(eladalon): TimeToSendPacket() can also return |true| in some
// situations where nothing actually ended up being sent to the network,
// and we probably don't want to update the budget in such cases.
// https://bugs.chromium.org/p/webrtc/issues/detail?id=8052
UpdateBudgetWithBytesSent(packet.bytes);
}
}
return success;
}
size_t PacedSender::SendPadding(size_t padding_needed,
const PacedPacketInfo& pacing_info) {
RTC_DCHECK_GT(packet_counter_, 0);
critsect_.Leave();
size_t bytes_sent =
packet_sender_->TimeToSendPadding(padding_needed, pacing_info);
critsect_.Enter();
if (bytes_sent > 0) {
UpdateBudgetWithBytesSent(bytes_sent);
}
return bytes_sent;
}
void PacedSender::UpdateBudgetWithElapsedTime(int64_t delta_time_ms) {
media_budget_->IncreaseBudget(delta_time_ms);
padding_budget_->IncreaseBudget(delta_time_ms);
}
void PacedSender::UpdateBudgetWithBytesSent(size_t bytes_sent) {
media_budget_->UseBudget(bytes_sent);
padding_budget_->UseBudget(bytes_sent);
}
void PacedSender::SetPacingFactor(float pacing_factor) {
rtc::CritScope cs(&critsect_);
pacing_factor_ = pacing_factor;
}
void PacedSender::SetQueueTimeLimit(int limit_ms) {
rtc::CritScope cs(&critsect_);
queue_time_limit = limit_ms;
}
} // namespace webrtc