bitrate_tracker.h

/*
 * bitrate_tracker.h - Bitrate tracking over running window
 * Ported from WebRTC (rtc_base/bitrate_tracker.h)
 *
 * Copyright (c) 2023 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 root of the source tree. An additional
 * intellectual property rights grant can be found in the file PATENTS.
 */

#ifndef BASE_BITRATE_TRACKER_H_
#define BASE_BITRATE_TRACKER_H_

#include <cstddef>
#include <cstdint>
#include <optional>

#include "base/rate_statistics.h"
#include "base/units/data_rate.h"
#include "base/units/data_size.h"
#include "base/units/time_delta.h"
#include "base/units/timestamp.h"

namespace ave {
namespace base {

using TimeDelta = ::ave::base::TimeDelta;
using Timestamp = ::ave::base::Timestamp;

// Class to estimate bitrates over running window.
// Timestamps used in Update(), Rate() and SetWindowSize() must never
// decrease for two consecutive calls.
// This class is thread unsafe.
class BitrateTracker {
 public:
  // max_window_sizes = Maximum window size for the rate estimation.
  //                    Initial window size is set to this, but may be changed
  //                    to something lower by calling SetWindowSize().
  explicit BitrateTracker(TimeDelta max_window_size);

  BitrateTracker(const BitrateTracker&) = default;
  BitrateTracker(BitrateTracker&&) = default;
  BitrateTracker& operator=(const BitrateTracker&) = delete;
  BitrateTracker& operator=(BitrateTracker&&) = delete;

  ~BitrateTracker() = default;

  // Resets instance to original state.
  void Reset() { impl_.Reset(); }

  // Updates bitrate with a new data point, moving averaging window as needed.
  void Update(int64_t bytes, Timestamp now);
  void Update(DataSize size, Timestamp now) { Update(size.bytes(), now); }

  // Returns bitrate, moving averaging window as needed.
  // Returns nullopt when bitrate can't be measured.
  std::optional<DataRate> Rate(Timestamp now) const;

  // Update the size of the averaging window. The maximum allowed value for
  // `window_size` is `max_window_size` as supplied in the constructor.
  bool SetWindowSize(TimeDelta window_size, Timestamp now);

 private:
  RateStatistics impl_;
};

}  // namespace base
}  // namespace ave

#endif  // BASE_BITRATE_TRACKER_H_