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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 "absl/memory/memory.h"
#include "api/rtc_event_log/rtc_event.h"
#include "api/rtc_event_log/rtc_event_log.h"
#include "logging/rtc_event_log/events/rtc_event_probe_cluster_created.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
#include "system_wrappers/include/metrics.h"
namespace webrtc {
namespace {
// The min probe packet size is scaled with the bitrate we're probing at.
// This defines the max min probe packet size, meaning that on high bitrates
// we have a min probe packet size of 200 bytes.
constexpr DataSize kMinProbePacketSize = DataSize::Bytes(200);
constexpr TimeDelta kProbeClusterTimeout = TimeDelta::Seconds(5);
} // namespace
BitrateProberConfig::BitrateProberConfig(
const FieldTrialsView* key_value_config)
: min_probe_delta("min_probe_delta", TimeDelta::Millis(1)),
max_probe_delay("max_probe_delay", TimeDelta::Millis(10)) {
ParseFieldTrial({&min_probe_delta, &max_probe_delay},
key_value_config->Lookup("WebRTC-Bwe-ProbingBehavior"));
}
BitrateProber::~BitrateProber() {
RTC_HISTOGRAM_COUNTS_1000("WebRTC.BWE.Probing.TotalProbeClustersRequested",
total_probe_count_);
RTC_HISTOGRAM_COUNTS_1000("WebRTC.BWE.Probing.TotalFailedProbeClusters",
total_failed_probe_count_);
}
BitrateProber::BitrateProber(const FieldTrialsView& field_trials)
: probing_state_(ProbingState::kDisabled),
next_probe_time_(Timestamp::PlusInfinity()),
total_probe_count_(0),
total_failed_probe_count_(0),
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";
}
}
void BitrateProber::OnIncomingPacket(DataSize packet_size) {
// Don't initialize probing unless we have something large enough to start
// probing.
if (probing_state_ == ProbingState::kInactive && !clusters_.empty() &&
packet_size >= std::min(RecommendedMinProbeSize(), kMinProbePacketSize)) {
// Send next probe right away.
next_probe_time_ = Timestamp::MinusInfinity();
probing_state_ = ProbingState::kActive;
}
}
void BitrateProber::CreateProbeCluster(
const ProbeClusterConfig& cluster_config) {
RTC_DCHECK(probing_state_ != ProbingState::kDisabled);
total_probe_count_++;
while (!clusters_.empty() &&
cluster_config.at_time - clusters_.front().requested_at >
kProbeClusterTimeout) {
clusters_.pop();
total_failed_probe_count_++;
}
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_bps = cluster_config.target_data_rate.bps();
cluster.pace_info.probe_cluster_id = cluster_config.id;
clusters_.push(cluster);
RTC_LOG(LS_INFO) << "Probe cluster (bitrate:min bytes:min packets): ("
<< cluster.pace_info.send_bitrate_bps << ":"
<< cluster.pace_info.probe_cluster_min_bytes << ":"
<< cluster.pace_info.probe_cluster_min_probes << ")";
// If we are already probing, continue to do so. Otherwise set it to
// kInactive and wait for OnIncomingPacket to start the probing.
if (probing_state_ != ProbingState::kActive)
probing_state_ = ProbingState::kInactive;
}
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::kSuspended;
return absl::nullopt;
}
}
PacedPacketInfo info = clusters_.front().pace_info;
info.probe_cluster_bytes_sent = clusters_.front().sent_bytes;
return info;
}
// Probe size is recommended based on the probe bitrate required. We choose
// a minimum of twice `kMinProbeDeltaMs` interval to allow scheduling to be
// feasible.
DataSize BitrateProber::RecommendedMinProbeSize() const {
if (clusters_.empty()) {
return DataSize::Zero();
}
DataRate send_rate =
DataRate::BitsPerSec(clusters_.front().pace_info.send_bitrate_bps);
return 2 * 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) {
RTC_HISTOGRAM_COUNTS_100000("WebRTC.BWE.Probing.ProbeClusterSizeInBytes",
cluster->sent_bytes);
RTC_HISTOGRAM_COUNTS_100("WebRTC.BWE.Probing.ProbesPerCluster",
cluster->sent_probes);
RTC_HISTOGRAM_COUNTS_10000("WebRTC.BWE.Probing.TimePerProbeCluster",
(now - cluster->started_at).ms());
clusters_.pop();
}
if (clusters_.empty()) {
probing_state_ = ProbingState::kSuspended;
}
}
}
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 =
DataRate::BitsPerSec(cluster.pace_info.send_bitrate_bps);
TimeDelta delta = sent_bytes / send_bitrate;
return cluster.started_at + delta;
}
} // namespace webrtc
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