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/*
* Copyright (c) 2014 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/bitrate_prober.h"
#include <algorithm>
#include "api/units/data_size.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
namespace webrtc {
namespace {
constexpr TimeDelta kProbeClusterTimeout = TimeDelta::Seconds(5);
constexpr size_t kMaxPendingProbeClusters = 5;
} // namespace
BitrateProberConfig::BitrateProberConfig(
const FieldTrialsView* key_value_config)
: min_probe_delta("min_probe_delta", TimeDelta::Millis(2)),
max_probe_delay("max_probe_delay", TimeDelta::Millis(10)),
min_packet_size("min_packet_size", DataSize::Bytes(200)) {
ParseFieldTrial({&min_probe_delta, &max_probe_delay, &min_packet_size},
key_value_config->Lookup("WebRTC-Bwe-ProbingBehavior"));
}
BitrateProber::BitrateProber(const FieldTrialsView& field_trials)
: probing_state_(ProbingState::kDisabled),
next_probe_time_(Timestamp::PlusInfinity()),
config_(&field_trials) {
SetEnabled(true);
}
void BitrateProber::SetEnabled(bool enable) {
if (enable) {
if (probing_state_ == ProbingState::kDisabled) {
probing_state_ = ProbingState::kInactive;
RTC_LOG(LS_INFO) << "Bandwidth probing enabled, set to inactive";
}
} else {
probing_state_ = ProbingState::kDisabled;
RTC_LOG(LS_INFO) << "Bandwidth probing disabled";
}
}
bool BitrateProber::ReadyToSetActiveState(DataSize packet_size) const {
if (clusters_.empty()) {
RTC_DCHECK(probing_state_ == ProbingState::kDisabled ||
probing_state_ == ProbingState::kInactive);
return false;
}
switch (probing_state_) {
case ProbingState::kDisabled:
case ProbingState::kActive:
return false;
case ProbingState::kInactive:
// If config_.min_packet_size > 0, a "large enough" packet must be sent
// first, before a probe can be generated and sent. Otherwise, send the
// probe asap.
return packet_size >=
std::min(RecommendedMinProbeSize(), config_.min_packet_size.Get());
}
}
void BitrateProber::OnIncomingPacket(DataSize packet_size) {
if (ReadyToSetActiveState(packet_size)) {
next_probe_time_ = Timestamp::MinusInfinity();
probing_state_ = ProbingState::kActive;
}
}
void BitrateProber::CreateProbeCluster(
const ProbeClusterConfig& cluster_config) {
RTC_DCHECK(probing_state_ != ProbingState::kDisabled);
while (!clusters_.empty() &&
(cluster_config.at_time - clusters_.front().requested_at >
kProbeClusterTimeout ||
clusters_.size() > kMaxPendingProbeClusters)) {
clusters_.pop();
}
ProbeCluster cluster;
cluster.requested_at = cluster_config.at_time;
cluster.pace_info.probe_cluster_min_probes =
cluster_config.target_probe_count;
cluster.pace_info.probe_cluster_min_bytes =
(cluster_config.target_data_rate * cluster_config.target_duration)
.bytes();
RTC_DCHECK_GE(cluster.pace_info.probe_cluster_min_bytes, 0);
cluster.pace_info.send_bitrate = cluster_config.target_data_rate;
cluster.pace_info.probe_cluster_id = cluster_config.id;
clusters_.push(cluster);
if (ReadyToSetActiveState(/*packet_size=*/DataSize::Zero())) {
next_probe_time_ = Timestamp::MinusInfinity();
probing_state_ = ProbingState::kActive;
}
RTC_DCHECK(probing_state_ == ProbingState::kActive ||
probing_state_ == ProbingState::kInactive);
RTC_LOG(LS_INFO) << "Probe cluster (bitrate_bps:min bytes:min packets): ("
<< cluster.pace_info.send_bitrate << ":"
<< cluster.pace_info.probe_cluster_min_bytes << ":"
<< cluster.pace_info.probe_cluster_min_probes << ", "
<< (probing_state_ == ProbingState::kInactive ? "Inactive"
: "Active")
<< ")";
}
Timestamp BitrateProber::NextProbeTime(Timestamp now) const {
// Probing is not active or probing is already complete.
if (probing_state_ != ProbingState::kActive || clusters_.empty()) {
return Timestamp::PlusInfinity();
}
return next_probe_time_;
}
absl::optional<PacedPacketInfo> BitrateProber::CurrentCluster(Timestamp now) {
if (clusters_.empty() || probing_state_ != ProbingState::kActive) {
return absl::nullopt;
}
if (next_probe_time_.IsFinite() &&
now - next_probe_time_ > config_.max_probe_delay.Get()) {
RTC_DLOG(LS_WARNING) << "Probe delay too high"
" (next_ms:"
<< next_probe_time_.ms() << ", now_ms: " << now.ms()
<< "), discarding probe cluster.";
clusters_.pop();
if (clusters_.empty()) {
probing_state_ = ProbingState::kInactive;
return absl::nullopt;
}
}
PacedPacketInfo info = clusters_.front().pace_info;
info.probe_cluster_bytes_sent = clusters_.front().sent_bytes;
return info;
}
DataSize BitrateProber::RecommendedMinProbeSize() const {
if (clusters_.empty()) {
return DataSize::Zero();
}
DataRate send_rate = clusters_.front().pace_info.send_bitrate;
return send_rate * config_.min_probe_delta;
}
void BitrateProber::ProbeSent(Timestamp now, DataSize size) {
RTC_DCHECK(probing_state_ == ProbingState::kActive);
RTC_DCHECK(!size.IsZero());
if (!clusters_.empty()) {
ProbeCluster* cluster = &clusters_.front();
if (cluster->sent_probes == 0) {
RTC_DCHECK(cluster->started_at.IsInfinite());
cluster->started_at = now;
}
cluster->sent_bytes += size.bytes<int>();
cluster->sent_probes += 1;
next_probe_time_ = CalculateNextProbeTime(*cluster);
if (cluster->sent_bytes >= cluster->pace_info.probe_cluster_min_bytes &&
cluster->sent_probes >= cluster->pace_info.probe_cluster_min_probes) {
clusters_.pop();
}
if (clusters_.empty()) {
probing_state_ = ProbingState::kInactive;
}
}
}
Timestamp BitrateProber::CalculateNextProbeTime(
const ProbeCluster& cluster) const {
RTC_CHECK_GT(cluster.pace_info.send_bitrate.bps(), 0);
RTC_CHECK(cluster.started_at.IsFinite());
// Compute the time delta from the cluster start to ensure probe bitrate stays
// close to the target bitrate. Result is in milliseconds.
DataSize sent_bytes = DataSize::Bytes(cluster.sent_bytes);
DataRate send_bitrate = cluster.pace_info.send_bitrate;
TimeDelta delta = sent_bytes / send_bitrate;
return cluster.started_at + delta;
}
} // namespace webrtc
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