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/*
* Copyright (c) 2018 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/pcc/monitor_interval.h"
#include <stddef.h>
#include <cmath>
#include "rtc_base/logging.h"
namespace webrtc {
namespace pcc {
PccMonitorInterval::PccMonitorInterval(DataRate target_sending_rate,
Timestamp start_time,
TimeDelta duration)
: target_sending_rate_(target_sending_rate),
start_time_(start_time),
interval_duration_(duration),
received_packets_size_(DataSize::Zero()),
feedback_collection_done_(false) {}
PccMonitorInterval::~PccMonitorInterval() = default;
PccMonitorInterval::PccMonitorInterval(const PccMonitorInterval& other) =
default;
void PccMonitorInterval::OnPacketsFeedback(
const std::vector<PacketResult>& packets_results) {
for (const PacketResult& packet_result : packets_results) {
if (packet_result.sent_packet.send_time <= start_time_) {
continue;
}
// Here we assume that if some packets are reordered with packets sent
// after the end of the monitor interval, then they are lost. (Otherwise
// it is not clear how long should we wait for packets feedback to arrive).
if (packet_result.sent_packet.send_time >
start_time_ + interval_duration_) {
feedback_collection_done_ = true;
return;
}
if (packet_result.receive_time.IsInfinite()) {
lost_packets_sent_time_.push_back(packet_result.sent_packet.send_time);
} else {
received_packets_.push_back(
{packet_result.receive_time - packet_result.sent_packet.send_time,
packet_result.sent_packet.send_time});
received_packets_size_ += packet_result.sent_packet.size;
}
}
}
// For the formula used in computations see formula for "slope" in the second
// method:
// https://www.johndcook.com/blog/2008/10/20/comparing-two-ways-to-fit-a-line-to-data/
double PccMonitorInterval::ComputeDelayGradient(
double delay_gradient_threshold) const {
// Early return to prevent division by 0 in case all packets are sent at the
// same time.
if (received_packets_.empty() || received_packets_.front().sent_time ==
received_packets_.back().sent_time) {
return 0;
}
double sum_times = 0;
double sum_delays = 0;
for (const ReceivedPacket& packet : received_packets_) {
double time_delta_us =
(packet.sent_time - received_packets_[0].sent_time).us();
double delay = packet.delay.us();
sum_times += time_delta_us;
sum_delays += delay;
}
double sum_squared_scaled_time_deltas = 0;
double sum_scaled_time_delta_dot_delay = 0;
for (const ReceivedPacket& packet : received_packets_) {
double time_delta_us =
(packet.sent_time - received_packets_[0].sent_time).us();
double delay = packet.delay.us();
double scaled_time_delta_us =
time_delta_us - sum_times / received_packets_.size();
sum_squared_scaled_time_deltas +=
scaled_time_delta_us * scaled_time_delta_us;
sum_scaled_time_delta_dot_delay += scaled_time_delta_us * delay;
}
double rtt_gradient =
sum_scaled_time_delta_dot_delay / sum_squared_scaled_time_deltas;
if (std::abs(rtt_gradient) < delay_gradient_threshold)
rtt_gradient = 0;
return rtt_gradient;
}
bool PccMonitorInterval::IsFeedbackCollectionDone() const {
return feedback_collection_done_;
}
Timestamp PccMonitorInterval::GetEndTime() const {
return start_time_ + interval_duration_;
}
double PccMonitorInterval::GetLossRate() const {
size_t packets_lost = lost_packets_sent_time_.size();
size_t packets_received = received_packets_.size();
if (packets_lost == 0)
return 0;
return static_cast<double>(packets_lost) / (packets_lost + packets_received);
}
DataRate PccMonitorInterval::GetTargetSendingRate() const {
return target_sending_rate_;
}
DataRate PccMonitorInterval::GetTransmittedPacketsRate() const {
if (received_packets_.empty()) {
return target_sending_rate_;
}
Timestamp receive_time_of_first_packet =
received_packets_.front().sent_time + received_packets_.front().delay;
Timestamp receive_time_of_last_packet =
received_packets_.back().sent_time + received_packets_.back().delay;
if (receive_time_of_first_packet == receive_time_of_last_packet) {
RTC_LOG(LS_WARNING)
<< "All packets in monitor interval were received at the same time.";
return target_sending_rate_;
}
return received_packets_size_ /
(receive_time_of_last_packet - receive_time_of_first_packet);
}
} // namespace pcc
} // namespace webrtc
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