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/*
* Copyright (c) 2024 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 "video/rate_utilization_tracker.h"
#include <algorithm>
namespace webrtc {
RateUtilizationTracker::RateUtilizationTracker(
size_t max_num_encoded_data_points,
TimeDelta max_duration)
: max_data_points_(max_num_encoded_data_points),
max_duration_(max_duration),
current_rate_(DataRate::Zero()) {
RTC_CHECK_GE(max_num_encoded_data_points, 0);
RTC_CHECK_GT(max_duration, TimeDelta::Zero());
}
void RateUtilizationTracker::OnDataRateChanged(DataRate rate, Timestamp time) {
current_rate_ = rate;
if (data_points_.empty()) {
// First entry should be contain first produced data, so just return after
// setting `current_rate_`.
return;
} else {
RateUsageUpdate& last_data_point = data_points_.back();
RTC_CHECK_GE(time, last_data_point.time);
if (last_data_point.time == time) {
last_data_point.target_rate = rate;
} else {
data_points_.push_back({.time = time,
.target_rate = rate,
.produced_data = DataSize::Zero()});
}
}
CullOldData(time);
}
void RateUtilizationTracker::OnDataProduced(DataSize size, Timestamp time) {
if (data_points_.empty()) {
data_points_.push_back(
{.time = time, .target_rate = current_rate_, .produced_data = size});
} else {
RateUsageUpdate& last_data_point = data_points_.back();
RTC_CHECK_GE(time, last_data_point.time);
if (last_data_point.time == time) {
last_data_point.produced_data += size;
} else {
data_points_.push_back(
{.time = time, .target_rate = current_rate_, .produced_data = size});
}
}
CullOldData(time);
}
absl::optional<double> RateUtilizationTracker::GetRateUtilizationFactor(
Timestamp time) const {
if (data_points_.empty()) {
return absl::nullopt;
}
RTC_CHECK_GE(time, data_points_.back().time);
DataSize allocated_send_data_size = DataSize::Zero();
DataSize total_produced_data = DataSize::Zero();
// Keep track of the last time data was produced - how much it was and how
// much rate budget has been allocated since then.
DataSize data_allocated_for_last_data = DataSize::Zero();
DataSize size_of_last_data = DataSize::Zero();
RTC_DCHECK(!data_points_.front().produced_data.IsZero());
for (size_t i = 0; i < data_points_.size(); ++i) {
const RateUsageUpdate& update = data_points_[i];
total_produced_data += update.produced_data;
DataSize allocated_since_previous_data_point =
i == 0 ? DataSize::Zero()
: (update.time - data_points_[i - 1].time) *
data_points_[i - 1].target_rate;
allocated_send_data_size += allocated_since_previous_data_point;
if (update.produced_data.IsZero()) {
// Just a rate update past the last seen produced data.
data_allocated_for_last_data =
std::min(size_of_last_data, data_allocated_for_last_data +
allocated_since_previous_data_point);
} else {
// A newer data point with produced data, reset accumulator for rate
// allocated past the last data point.
size_of_last_data = update.produced_data;
data_allocated_for_last_data = DataSize::Zero();
}
}
if (allocated_send_data_size.IsZero() && current_rate_.IsZero()) {
// No allocated rate across all of the data points, ignore.
return absl::nullopt;
}
// Calculate the rate past the very last data point until the polling time.
const RateUsageUpdate& last_update = data_points_.back();
DataSize allocated_since_last_data_point =
(time - last_update.time) * last_update.target_rate;
// If the last produced data packet is larger than the accumulated rate
// allocation window since then, use that data point size instead (minus any
// data rate accumulated in rate updates after that data point was produced).
allocated_send_data_size +=
std::max(allocated_since_last_data_point,
size_of_last_data - data_allocated_for_last_data);
return total_produced_data.bytes<double>() / allocated_send_data_size.bytes();
}
void RateUtilizationTracker::CullOldData(Timestamp time) {
// Remove data points that are either too old, exceed the limit of number of
// data points - and make sure the first entry in the list contains actual
// data produced since we calculate send usage since that time.
// We don't allow negative times so always start window at absolute time >= 0.
const Timestamp oldest_included_time =
time.ms() > max_duration_.ms() ? time - max_duration_ : Timestamp::Zero();
while (!data_points_.empty() &&
(data_points_.front().time < oldest_included_time ||
data_points_.size() > max_data_points_ ||
data_points_.front().produced_data.IsZero())) {
data_points_.pop_front();
}
}
} // namespace webrtc