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/*
* Copyright (c) 2016 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/goog_cc/probe_bitrate_estimator.h"
#include <algorithm>
#include <memory>
#include "absl/types/optional.h"
#include "api/rtc_event_log/rtc_event_log.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 "logging/rtc_event_log/events/rtc_event_probe_result_failure.h"
#include "logging/rtc_event_log/events/rtc_event_probe_result_success.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
namespace webrtc {
namespace {
// The minumum number of probes we need to receive feedback about in percent
// in order to have a valid estimate.
constexpr double kMinReceivedProbesRatio = .80;
// The minumum number of bytes we need to receive feedback about in percent
// in order to have a valid estimate.
constexpr double kMinReceivedBytesRatio = .80;
// The maximum |receive rate| / |send rate| ratio for a valid estimate.
constexpr float kMaxValidRatio = 2.0f;
// The minimum |receive rate| / |send rate| ratio assuming that the link is
// not saturated, i.e. we assume that we will receive at least
// kMinRatioForUnsaturatedLink * |send rate| if |send rate| is less than the
// link capacity.
constexpr float kMinRatioForUnsaturatedLink = 0.9f;
// The target utilization of the link. If we know true link capacity
// we'd like to send at 95% of that rate.
constexpr float kTargetUtilizationFraction = 0.95f;
// The maximum time period over which the cluster history is retained.
// This is also the maximum time period beyond which a probing burst is not
// expected to last.
constexpr TimeDelta kMaxClusterHistory = TimeDelta::Seconds(1);
// The maximum time interval between first and the last probe on a cluster
// on the sender side as well as the receive side.
constexpr TimeDelta kMaxProbeInterval = TimeDelta::Seconds(1);
} // namespace
ProbeBitrateEstimator::ProbeBitrateEstimator(RtcEventLog* event_log)
: event_log_(event_log) {}
ProbeBitrateEstimator::~ProbeBitrateEstimator() = default;
absl::optional<DataRate> ProbeBitrateEstimator::HandleProbeAndEstimateBitrate(
const PacketResult& packet_feedback) {
int cluster_id = packet_feedback.sent_packet.pacing_info.probe_cluster_id;
RTC_DCHECK_NE(cluster_id, PacedPacketInfo::kNotAProbe);
EraseOldClusters(packet_feedback.receive_time);
AggregatedCluster* cluster = &clusters_[cluster_id];
if (packet_feedback.sent_packet.send_time < cluster->first_send) {
cluster->first_send = packet_feedback.sent_packet.send_time;
}
if (packet_feedback.sent_packet.send_time > cluster->last_send) {
cluster->last_send = packet_feedback.sent_packet.send_time;
cluster->size_last_send = packet_feedback.sent_packet.size;
}
if (packet_feedback.receive_time < cluster->first_receive) {
cluster->first_receive = packet_feedback.receive_time;
cluster->size_first_receive = packet_feedback.sent_packet.size;
}
if (packet_feedback.receive_time > cluster->last_receive) {
cluster->last_receive = packet_feedback.receive_time;
}
cluster->size_total += packet_feedback.sent_packet.size;
cluster->num_probes += 1;
RTC_DCHECK_GT(
packet_feedback.sent_packet.pacing_info.probe_cluster_min_probes, 0);
RTC_DCHECK_GT(packet_feedback.sent_packet.pacing_info.probe_cluster_min_bytes,
0);
int min_probes =
packet_feedback.sent_packet.pacing_info.probe_cluster_min_probes *
kMinReceivedProbesRatio;
DataSize min_size =
DataSize::Bytes(
packet_feedback.sent_packet.pacing_info.probe_cluster_min_bytes) *
kMinReceivedBytesRatio;
if (cluster->num_probes < min_probes || cluster->size_total < min_size)
return absl::nullopt;
TimeDelta send_interval = cluster->last_send - cluster->first_send;
TimeDelta receive_interval = cluster->last_receive - cluster->first_receive;
if (send_interval <= TimeDelta::Zero() || send_interval > kMaxProbeInterval ||
receive_interval <= TimeDelta::Zero() ||
receive_interval > kMaxProbeInterval) {
RTC_LOG(LS_INFO) << "Probing unsuccessful, invalid send/receive interval"
" [cluster id: "
<< cluster_id
<< "] [send interval: " << ToString(send_interval)
<< "]"
" [receive interval: "
<< ToString(receive_interval) << "]";
if (event_log_) {
event_log_->Log(std::make_unique<RtcEventProbeResultFailure>(
cluster_id, ProbeFailureReason::kInvalidSendReceiveInterval));
}
return absl::nullopt;
}
// Since the `send_interval` does not include the time it takes to actually
// send the last packet the size of the last sent packet should not be
// included when calculating the send bitrate.
RTC_DCHECK_GT(cluster->size_total, cluster->size_last_send);
DataSize send_size = cluster->size_total - cluster->size_last_send;
DataRate send_rate = send_size / send_interval;
// Since the `receive_interval` does not include the time it takes to
// actually receive the first packet the size of the first received packet
// should not be included when calculating the receive bitrate.
RTC_DCHECK_GT(cluster->size_total, cluster->size_first_receive);
DataSize receive_size = cluster->size_total - cluster->size_first_receive;
DataRate receive_rate = receive_size / receive_interval;
double ratio = receive_rate / send_rate;
if (ratio > kMaxValidRatio) {
RTC_LOG(LS_INFO) << "Probing unsuccessful, receive/send ratio too high"
" [cluster id: "
<< cluster_id << "] [send: " << ToString(send_size)
<< " / " << ToString(send_interval) << " = "
<< ToString(send_rate)
<< "]"
" [receive: "
<< ToString(receive_size) << " / "
<< ToString(receive_interval) << " = "
<< ToString(receive_rate)
<< " ]"
" [ratio: "
<< ToString(receive_rate) << " / " << ToString(send_rate)
<< " = " << ratio << " > kMaxValidRatio ("
<< kMaxValidRatio << ")]";
if (event_log_) {
event_log_->Log(std::make_unique<RtcEventProbeResultFailure>(
cluster_id, ProbeFailureReason::kInvalidSendReceiveRatio));
}
return absl::nullopt;
}
RTC_LOG(LS_INFO) << "Probing successful"
" [cluster id: "
<< cluster_id << "] [send: " << ToString(send_size) << " / "
<< ToString(send_interval) << " = " << ToString(send_rate)
<< " ]"
" [receive: "
<< ToString(receive_size) << " / "
<< ToString(receive_interval) << " = "
<< ToString(receive_rate) << "]";
DataRate res = std::min(send_rate, receive_rate);
// If we're receiving at significantly lower bitrate than we were sending at,
// it suggests that we've found the true capacity of the link. In this case,
// set the target bitrate slightly lower to not immediately overuse.
if (receive_rate < kMinRatioForUnsaturatedLink * send_rate) {
RTC_DCHECK_GT(send_rate, receive_rate);
res = kTargetUtilizationFraction * receive_rate;
}
if (event_log_) {
event_log_->Log(
std::make_unique<RtcEventProbeResultSuccess>(cluster_id, res.bps()));
}
estimated_data_rate_ = res;
return estimated_data_rate_;
}
absl::optional<DataRate>
ProbeBitrateEstimator::FetchAndResetLastEstimatedBitrate() {
absl::optional<DataRate> estimated_data_rate = estimated_data_rate_;
estimated_data_rate_.reset();
return estimated_data_rate;
}
void ProbeBitrateEstimator::EraseOldClusters(Timestamp timestamp) {
for (auto it = clusters_.begin(); it != clusters_.end();) {
if (it->second.last_receive + kMaxClusterHistory < timestamp) {
it = clusters_.erase(it);
} else {
++it;
}
}
}
} // namespace webrtc
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