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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.
*/
#ifndef VIDEO_RATE_UTILIZATION_TRACKER_H_
#define VIDEO_RATE_UTILIZATION_TRACKER_H_
#include <deque>
#include "absl/types/optional.h"
#include "api/units/data_rate.h"
#include "api/units/data_size.h"
#include "api/units/time_delta.h"
#include "api/units/timestamp.h"
namespace webrtc {
// Helper class that tracks the rate of utilization over a sliding window.
// tl;dr: if an encoder has a target rate of 1000kbps but in practice
// produces 500kbps it would have a utilization factor of 0.5.
// The tracker looks only at discrete events, and keeps only a fixed amount
// of data points (e.g. encoded frames) or points newer than a given time
// limit, whichever is lower.
// More precisely This class measures the allocated cumulative byte budget (as
// specified by one or more rate updates) and the actual cumulative number of
// bytes produced over a sliding window. A utilization factor (produced bytes /
// budgeted bytes) is calculated seen from the first data point timestamp until
// the last data point timestamp plus the amount time needed to send that last
// data point given no further updates to the rate. The implication of this is a
// smoother value, and e.g. setting a rate and adding a data point, then
// immediately querying the utilization reports 1.0 utilization instead of some
// undefined state.
class RateUtilizationTracker {
public:
RateUtilizationTracker(size_t max_num_encoded_data_points,
TimeDelta max_duration);
// The timestamps used should never decrease relative the last one.
void OnDataRateChanged(DataRate rate, Timestamp time);
void OnDataProduced(DataSize size, Timestamp time);
absl::optional<double> GetRateUtilizationFactor(Timestamp time) const;
private:
struct RateUsageUpdate {
Timestamp time;
DataRate target_rate;
DataSize produced_data;
};
void CullOldData(Timestamp time);
const size_t max_data_points_;
const TimeDelta max_duration_;
DataRate current_rate_;
std::deque<RateUsageUpdate> data_points_;
};
} // namespace webrtc
#endif // VIDEO_RATE_UTILIZATION_TRACKER_H_