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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/congestion_controller/include/send_side_congestion_controller.h"
#include <algorithm>
#include <cstdio>
#include <iterator>
#include <memory>
#include <vector>
#include "absl/memory/memory.h"
#include "modules/bitrate_controller/include/bitrate_controller.h"
#include "modules/congestion_controller/congestion_window_pushback_controller.h"
#include "modules/congestion_controller/goog_cc/acknowledged_bitrate_estimator.h"
#include "modules/congestion_controller/goog_cc/probe_controller.h"
#include "modules/remote_bitrate_estimator/include/bwe_defines.h"
#include "rtc_base/checks.h"
#include "rtc_base/format_macros.h"
#include "rtc_base/logging.h"
#include "rtc_base/numerics/safe_conversions.h"
#include "rtc_base/rate_limiter.h"
#include "rtc_base/socket.h"
#include "rtc_base/timeutils.h"
#include "system_wrappers/include/field_trial.h"
#include "system_wrappers/include/runtime_enabled_features.h"
namespace webrtc {
namespace {
const char kCwndExperiment[] = "WebRTC-CwndExperiment";
const char kPacerPushbackExperiment[] = "WebRTC-PacerPushbackExperiment";
// When CongestionWindowPushback is enabled, the pacer is oblivious to
// the congestion window. The relation between outstanding data and
// the congestion window affects encoder allocations directly.
const char kCongestionPushbackExperiment[] = "WebRTC-CongestionWindowPushback";
const int64_t kDefaultAcceptedQueueMs = 250;
bool CwndExperimentEnabled() {
std::string experiment_string =
webrtc::field_trial::FindFullName(kCwndExperiment);
// The experiment is enabled iff the field trial string begins with "Enabled".
return experiment_string.find("Enabled") == 0;
}
bool ReadCwndExperimentParameter(int64_t* accepted_queue_ms) {
RTC_DCHECK(accepted_queue_ms);
std::string experiment_string =
webrtc::field_trial::FindFullName(kCwndExperiment);
int parsed_values =
sscanf(experiment_string.c_str(), "Enabled-%" PRId64, accepted_queue_ms);
if (parsed_values == 1) {
RTC_CHECK_GE(*accepted_queue_ms, 0)
<< "Accepted must be greater than or equal to 0.";
return true;
}
return false;
}
bool IsCongestionWindowPushbackExperimentEnabled() {
return webrtc::field_trial::IsEnabled(kCongestionPushbackExperiment) &&
webrtc::field_trial::IsEnabled(kCwndExperiment);
}
std::unique_ptr<CongestionWindowPushbackController>
MaybeCreateCongestionWindowPushbackController() {
return IsCongestionWindowPushbackExperimentEnabled()
? absl::make_unique<CongestionWindowPushbackController>()
: nullptr;
}
static const int64_t kRetransmitWindowSizeMs = 500;
// Makes sure that the bitrate and the min, max values are in valid range.
static void ClampBitrates(int* bitrate_bps,
int* min_bitrate_bps,
int* max_bitrate_bps) {
// TODO(holmer): We should make sure the default bitrates are set to 10 kbps,
// and that we don't try to set the min bitrate to 0 from any applications.
// The congestion controller should allow a min bitrate of 0.
if (*min_bitrate_bps < congestion_controller::GetMinBitrateBps())
*min_bitrate_bps = congestion_controller::GetMinBitrateBps();
if (*max_bitrate_bps > 0)
*max_bitrate_bps = std::max(*min_bitrate_bps, *max_bitrate_bps);
if (*bitrate_bps > 0)
*bitrate_bps = std::max(*min_bitrate_bps, *bitrate_bps);
}
std::vector<webrtc::PacketFeedback> ReceivedPacketFeedbackVector(
const std::vector<webrtc::PacketFeedback>& input) {
std::vector<PacketFeedback> received_packet_feedback_vector;
auto is_received = [](const webrtc::PacketFeedback& packet_feedback) {
return packet_feedback.arrival_time_ms !=
webrtc::PacketFeedback::kNotReceived;
};
std::copy_if(input.begin(), input.end(),
std::back_inserter(received_packet_feedback_vector),
is_received);
return received_packet_feedback_vector;
}
void SortPacketFeedbackVector(
std::vector<webrtc::PacketFeedback>* const input) {
RTC_DCHECK(input);
std::sort(input->begin(), input->end(), PacketFeedbackComparator());
}
bool IsPacerPushbackExperimentEnabled() {
return webrtc::field_trial::IsEnabled(kPacerPushbackExperiment) ||
(!webrtc::field_trial::IsDisabled(kPacerPushbackExperiment) &&
webrtc::runtime_enabled_features::IsFeatureEnabled(
webrtc::runtime_enabled_features::kDualStreamModeFeatureName));
}
} // namespace
SendSideCongestionController::SendSideCongestionController(
const Clock* clock,
Observer* observer,
RtcEventLog* event_log,
PacedSender* pacer)
: clock_(clock),
observer_(observer),
event_log_(event_log),
pacer_(pacer),
bitrate_controller_(
BitrateController::CreateBitrateController(clock_, event_log)),
acknowledged_bitrate_estimator_(
absl::make_unique<AcknowledgedBitrateEstimator>()),
probe_controller_(new ProbeController()),
retransmission_rate_limiter_(
new RateLimiter(clock, kRetransmitWindowSizeMs)),
transport_feedback_adapter_(clock_),
last_reported_bitrate_bps_(0),
last_reported_fraction_loss_(0),
last_reported_rtt_(0),
network_state_(kNetworkUp),
pause_pacer_(false),
pacer_paused_(false),
min_bitrate_bps_(congestion_controller::GetMinBitrateBps()),
delay_based_bwe_(new DelayBasedBwe(event_log_)),
in_cwnd_experiment_(CwndExperimentEnabled()),
accepted_queue_ms_(kDefaultAcceptedQueueMs),
was_in_alr_(false),
send_side_bwe_with_overhead_(
webrtc::field_trial::IsEnabled("WebRTC-SendSideBwe-WithOverhead")),
transport_overhead_bytes_per_packet_(0),
pacer_pushback_experiment_(IsPacerPushbackExperimentEnabled()),
congestion_window_pushback_controller_(
MaybeCreateCongestionWindowPushbackController()) {
delay_based_bwe_->SetMinBitrate(min_bitrate_bps_);
if (in_cwnd_experiment_ &&
!ReadCwndExperimentParameter(&accepted_queue_ms_)) {
RTC_LOG(LS_WARNING) << "Failed to parse parameters for CwndExperiment "
"from field trial string. Experiment disabled.";
in_cwnd_experiment_ = false;
}
}
SendSideCongestionController::~SendSideCongestionController() {}
void SendSideCongestionController::RegisterPacketFeedbackObserver(
PacketFeedbackObserver* observer) {
transport_feedback_adapter_.RegisterPacketFeedbackObserver(observer);
}
void SendSideCongestionController::DeRegisterPacketFeedbackObserver(
PacketFeedbackObserver* observer) {
transport_feedback_adapter_.DeRegisterPacketFeedbackObserver(observer);
}
void SendSideCongestionController::RegisterNetworkObserver(Observer* observer) {
rtc::CritScope cs(&observer_lock_);
RTC_DCHECK(observer_ == nullptr);
observer_ = observer;
}
void SendSideCongestionController::DeRegisterNetworkObserver(
Observer* observer) {
rtc::CritScope cs(&observer_lock_);
RTC_DCHECK_EQ(observer_, observer);
observer_ = nullptr;
}
void SendSideCongestionController::SetBweBitrates(int min_bitrate_bps,
int start_bitrate_bps,
int max_bitrate_bps) {
ClampBitrates(&start_bitrate_bps, &min_bitrate_bps, &max_bitrate_bps);
bitrate_controller_->SetBitrates(start_bitrate_bps, min_bitrate_bps,
max_bitrate_bps);
{
rtc::CritScope cs(&probe_lock_);
SendProbes(probe_controller_->SetBitrates(
min_bitrate_bps, start_bitrate_bps, max_bitrate_bps,
clock_->TimeInMilliseconds()));
}
{
rtc::CritScope cs(&bwe_lock_);
if (start_bitrate_bps > 0)
delay_based_bwe_->SetStartBitrate(start_bitrate_bps);
min_bitrate_bps_ = min_bitrate_bps;
delay_based_bwe_->SetMinBitrate(min_bitrate_bps_);
}
MaybeTriggerOnNetworkChanged();
}
void SendSideCongestionController::SetAllocatedSendBitrateLimits(
int64_t min_send_bitrate_bps,
int64_t max_padding_bitrate_bps,
int64_t max_total_bitrate_bps) {
pacer_->SetSendBitrateLimits(min_send_bitrate_bps, max_padding_bitrate_bps);
rtc::CritScope cs(&probe_lock_);
SendProbes(probe_controller_->OnMaxTotalAllocatedBitrate(
max_total_bitrate_bps, clock_->TimeInMilliseconds()));
}
// TODO(holmer): Split this up and use SetBweBitrates in combination with
// OnNetworkRouteChanged.
void SendSideCongestionController::OnNetworkRouteChanged(
const rtc::NetworkRoute& network_route,
int bitrate_bps,
int min_bitrate_bps,
int max_bitrate_bps) {
ClampBitrates(&bitrate_bps, &min_bitrate_bps, &max_bitrate_bps);
// TODO(honghaiz): Recreate this object once the bitrate controller is
// no longer exposed outside SendSideCongestionController.
bitrate_controller_->ResetBitrates(bitrate_bps, min_bitrate_bps,
max_bitrate_bps);
transport_feedback_adapter_.SetNetworkIds(network_route.local_network_id,
network_route.remote_network_id);
{
rtc::CritScope cs(&bwe_lock_);
transport_overhead_bytes_per_packet_ = network_route.packet_overhead;
min_bitrate_bps_ = min_bitrate_bps;
delay_based_bwe_.reset(new DelayBasedBwe(event_log_));
acknowledged_bitrate_estimator_.reset(new AcknowledgedBitrateEstimator());
delay_based_bwe_->SetStartBitrate(bitrate_bps);
delay_based_bwe_->SetMinBitrate(min_bitrate_bps);
}
{
rtc::CritScope cs(&probe_lock_);
probe_controller_->Reset(clock_->TimeInMilliseconds());
SendProbes(probe_controller_->SetBitrates(min_bitrate_bps, bitrate_bps,
max_bitrate_bps,
clock_->TimeInMilliseconds()));
}
MaybeTriggerOnNetworkChanged();
}
BitrateController* SendSideCongestionController::GetBitrateController() const {
return bitrate_controller_.get();
}
bool SendSideCongestionController::AvailableBandwidth(
uint32_t* bandwidth) const {
return bitrate_controller_->AvailableBandwidth(bandwidth);
}
RtcpBandwidthObserver* SendSideCongestionController::GetBandwidthObserver() {
return bitrate_controller_.get();
}
RtcpBandwidthObserver* SendSideCongestionController::GetBandwidthObserver()
const {
return bitrate_controller_.get();
}
RateLimiter* SendSideCongestionController::GetRetransmissionRateLimiter() {
return retransmission_rate_limiter_.get();
}
void SendSideCongestionController::SetPerPacketFeedbackAvailable(
bool available) {}
void SendSideCongestionController::EnablePeriodicAlrProbing(bool enable) {
rtc::CritScope cs(&probe_lock_);
probe_controller_->EnablePeriodicAlrProbing(enable);
}
int64_t SendSideCongestionController::GetPacerQueuingDelayMs() const {
return IsNetworkDown() ? 0 : pacer_->QueueInMs();
}
int64_t SendSideCongestionController::GetFirstPacketTimeMs() const {
return pacer_->FirstSentPacketTimeMs();
}
TransportFeedbackObserver*
SendSideCongestionController::GetTransportFeedbackObserver() {
return this;
}
void SendSideCongestionController::SignalNetworkState(NetworkState state) {
RTC_LOG(LS_INFO) << "SignalNetworkState "
<< (state == kNetworkUp ? "Up" : "Down");
{
rtc::CritScope cs(&network_state_lock_);
pause_pacer_ = state == kNetworkDown;
network_state_ = state;
}
{
rtc::CritScope cs(&probe_lock_);
NetworkAvailability msg;
msg.at_time = Timestamp::ms(clock_->TimeInMilliseconds());
msg.network_available = state == kNetworkUp;
SendProbes(probe_controller_->OnNetworkAvailability(msg));
}
MaybeTriggerOnNetworkChanged();
}
void SendSideCongestionController::SetTransportOverhead(
size_t transport_overhead_bytes_per_packet) {
rtc::CritScope cs(&bwe_lock_);
transport_overhead_bytes_per_packet_ = transport_overhead_bytes_per_packet;
}
void SendSideCongestionController::OnSentPacket(
const rtc::SentPacket& sent_packet) {
// We're not interested in packets without an id, which may be stun packets,
// etc, sent on the same transport.
if (sent_packet.packet_id == -1)
return;
transport_feedback_adapter_.OnSentPacket(sent_packet.packet_id,
sent_packet.send_time_ms);
if (in_cwnd_experiment_)
LimitOutstandingBytes(transport_feedback_adapter_.GetOutstandingBytes());
}
void SendSideCongestionController::OnRttUpdate(int64_t avg_rtt_ms,
int64_t max_rtt_ms) {
rtc::CritScope cs(&bwe_lock_);
delay_based_bwe_->OnRttUpdate(avg_rtt_ms);
}
int64_t SendSideCongestionController::TimeUntilNextProcess() {
return bitrate_controller_->TimeUntilNextProcess();
}
void SendSideCongestionController::SendProbes(
std::vector<ProbeClusterConfig> probe_configs) {
for (auto probe_config : probe_configs) {
pacer_->CreateProbeCluster(probe_config.target_data_rate.bps());
}
}
void SendSideCongestionController::Process() {
bool pause_pacer;
// TODO(holmer): Once this class is running on a task queue we should
// replace this with a task instead.
{
rtc::CritScope lock(&network_state_lock_);
pause_pacer = pause_pacer_;
}
if (pause_pacer && !pacer_paused_) {
pacer_->Pause();
pacer_paused_ = true;
} else if (!pause_pacer && pacer_paused_) {
pacer_->Resume();
pacer_paused_ = false;
}
bitrate_controller_->Process();
{
rtc::CritScope cs(&probe_lock_);
probe_controller_->SetAlrStartTimeMs(
pacer_->GetApplicationLimitedRegionStartTime());
SendProbes(probe_controller_->Process(clock_->TimeInMilliseconds()));
}
MaybeTriggerOnNetworkChanged();
}
void SendSideCongestionController::AddPacket(
uint32_t ssrc,
uint16_t sequence_number,
size_t length,
const PacedPacketInfo& pacing_info) {
if (send_side_bwe_with_overhead_) {
rtc::CritScope cs(&bwe_lock_);
length += transport_overhead_bytes_per_packet_;
}
transport_feedback_adapter_.AddPacket(ssrc, sequence_number, length,
pacing_info);
}
void SendSideCongestionController::OnTransportFeedback(
const rtcp::TransportFeedback& feedback) {
RTC_DCHECK_RUNS_SERIALIZED(&worker_race_);
transport_feedback_adapter_.OnTransportFeedback(feedback);
std::vector<PacketFeedback> feedback_vector = ReceivedPacketFeedbackVector(
transport_feedback_adapter_.GetTransportFeedbackVector());
SortPacketFeedbackVector(&feedback_vector);
bool currently_in_alr =
pacer_->GetApplicationLimitedRegionStartTime().has_value();
if (was_in_alr_ && !currently_in_alr) {
int64_t now_ms = rtc::TimeMillis();
acknowledged_bitrate_estimator_->SetAlrEndedTimeMs(now_ms);
rtc::CritScope cs(&probe_lock_);
probe_controller_->SetAlrEndedTimeMs(now_ms);
}
was_in_alr_ = currently_in_alr;
acknowledged_bitrate_estimator_->IncomingPacketFeedbackVector(
feedback_vector);
DelayBasedBwe::Result result;
{
rtc::CritScope cs(&bwe_lock_);
result = delay_based_bwe_->IncomingPacketFeedbackVector(
feedback_vector, acknowledged_bitrate_estimator_->bitrate_bps(),
clock_->TimeInMilliseconds());
}
if (result.updated) {
bitrate_controller_->OnDelayBasedBweResult(result);
// Update the estimate in the ProbeController, in case we want to probe.
MaybeTriggerOnNetworkChanged();
}
if (result.recovered_from_overuse) {
rtc::CritScope cs(&probe_lock_);
probe_controller_->SetAlrStartTimeMs(
pacer_->GetApplicationLimitedRegionStartTime());
SendProbes(probe_controller_->RequestProbe(clock_->TimeInMilliseconds()));
}
if (in_cwnd_experiment_) {
LimitOutstandingBytes(transport_feedback_adapter_.GetOutstandingBytes());
}
}
void SendSideCongestionController::LimitOutstandingBytes(
size_t num_outstanding_bytes) {
RTC_DCHECK(in_cwnd_experiment_);
rtc::CritScope lock(&network_state_lock_);
absl::optional<int64_t> min_rtt_ms =
transport_feedback_adapter_.GetMinFeedbackLoopRtt();
// No valid RTT. Could be because send-side BWE isn't used, in which case
// we don't try to limit the outstanding packets.
if (!min_rtt_ms)
return;
const size_t kMinCwndBytes = 2 * 1500;
size_t max_outstanding_bytes =
std::max<size_t>((*min_rtt_ms + accepted_queue_ms_) *
last_reported_bitrate_bps_ / 1000 / 8,
kMinCwndBytes);
RTC_LOG(LS_INFO) << clock_->TimeInMilliseconds()
<< " Outstanding bytes: " << num_outstanding_bytes
<< " pacer queue: " << pacer_->QueueInMs()
<< " max outstanding: " << max_outstanding_bytes;
RTC_LOG(LS_INFO) << "Feedback rtt: " << *min_rtt_ms
<< " Bitrate: " << last_reported_bitrate_bps_;
if (congestion_window_pushback_controller_) {
congestion_window_pushback_controller_->UpdateOutstandingData(
num_outstanding_bytes);
congestion_window_pushback_controller_->UpdateMaxOutstandingData(
max_outstanding_bytes);
} else {
pause_pacer_ = num_outstanding_bytes > max_outstanding_bytes;
}
}
std::vector<PacketFeedback>
SendSideCongestionController::GetTransportFeedbackVector() const {
RTC_DCHECK_RUNS_SERIALIZED(&worker_race_);
return transport_feedback_adapter_.GetTransportFeedbackVector();
}
void SendSideCongestionController::SetPacingFactor(float pacing_factor) {
pacer_->SetPacingFactor(pacing_factor);
}
void SendSideCongestionController::SetAllocatedBitrateWithoutFeedback(
uint32_t bitrate_bps) {
acknowledged_bitrate_estimator_->SetAllocatedBitrateWithoutFeedback(
bitrate_bps);
}
void SendSideCongestionController::MaybeTriggerOnNetworkChanged() {
uint32_t bitrate_bps;
uint8_t fraction_loss;
int64_t rtt;
bool estimate_changed = bitrate_controller_->GetNetworkParameters(
&bitrate_bps, &fraction_loss, &rtt);
if (estimate_changed) {
pacer_->SetEstimatedBitrate(bitrate_bps);
{
rtc::CritScope cs(&probe_lock_);
SendProbes(probe_controller_->SetEstimatedBitrate(
bitrate_bps, clock_->TimeInMilliseconds()));
}
retransmission_rate_limiter_->SetMaxRate(bitrate_bps);
}
if (IsNetworkDown()) {
bitrate_bps = 0;
} else if (congestion_window_pushback_controller_) {
rtc::CritScope lock(&network_state_lock_);
bitrate_bps = congestion_window_pushback_controller_->UpdateTargetBitrate(
bitrate_bps);
} else if (!pacer_pushback_experiment_) {
bitrate_bps = IsSendQueueFull() ? 0 : bitrate_bps;
} else {
int64_t queue_length_ms = pacer_->ExpectedQueueTimeMs();
if (queue_length_ms == 0) {
encoding_rate_ = 1.0;
} else if (queue_length_ms > 50) {
float encoding_rate = 1.0 - queue_length_ms / 1000.0;
encoding_rate_ = std::min(encoding_rate_, encoding_rate);
encoding_rate_ = std::max(encoding_rate_, 0.0f);
}
bitrate_bps *= encoding_rate_;
bitrate_bps = bitrate_bps < 50000 ? 0 : bitrate_bps;
}
if (HasNetworkParametersToReportChanged(bitrate_bps, fraction_loss, rtt)) {
int64_t probing_interval_ms;
{
rtc::CritScope cs(&bwe_lock_);
probing_interval_ms = delay_based_bwe_->GetExpectedBwePeriodMs();
}
{
rtc::CritScope cs(&observer_lock_);
if (observer_) {
observer_->OnNetworkChanged(bitrate_bps, fraction_loss, rtt,
probing_interval_ms);
}
}
}
}
bool SendSideCongestionController::HasNetworkParametersToReportChanged(
uint32_t bitrate_bps,
uint8_t fraction_loss,
int64_t rtt) {
rtc::CritScope cs(&network_state_lock_);
bool changed =
last_reported_bitrate_bps_ != bitrate_bps ||
(bitrate_bps > 0 && (last_reported_fraction_loss_ != fraction_loss ||
last_reported_rtt_ != rtt));
if (changed && (last_reported_bitrate_bps_ == 0 || bitrate_bps == 0)) {
RTC_LOG(LS_INFO) << "Bitrate estimate state changed, BWE: " << bitrate_bps
<< " bps.";
}
last_reported_bitrate_bps_ = bitrate_bps;
last_reported_fraction_loss_ = fraction_loss;
last_reported_rtt_ = rtt;
return changed;
}
bool SendSideCongestionController::IsSendQueueFull() const {
return pacer_->ExpectedQueueTimeMs() > PacedSender::kMaxQueueLengthMs;
}
bool SendSideCongestionController::IsNetworkDown() const {
rtc::CritScope cs(&network_state_lock_);
return network_state_ == kNetworkDown;
}
} // namespace webrtc