encoder_overshoot_detector.h

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/*

 *  Copyright (c) 2019 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_ENCODER_OVERSHOOT_DETECTOR_H_

#define VIDEO_ENCODER_OVERSHOOT_DETECTOR_H_

#include <deque>

#include "absl/types/optional.h"

#include "api/units/data_rate.h"

#include "api/video_codecs/video_codec.h"

namespace webrtc {

class EncoderOvershootDetector {

 public:

  explicit EncoderOvershootDetector(int64_t window_size_ms,

                                    VideoCodecType codec,

                                    bool is_screenshare);

  ~EncoderOvershootDetector();

  void SetTargetRate(DataRate target_bitrate,

                     double target_framerate_fps,

                     int64_t time_ms);

  // A frame has been encoded or dropped. `bytes` == 0 indicates a drop.

  void OnEncodedFrame(size_t bytes, int64_t time_ms);

  // This utilization factor reaches 1.0 only if the encoder produces encoded

  // frame in such a way that they can be sent onto the network at

  // `target_bitrate` without building growing queues.

  absl::optional<double> GetNetworkRateUtilizationFactor(int64_t time_ms);

  // This utilization factor is based just on actual encoded frame sizes in

  // relation to ideal sizes. An undershoot may be compensated by an

  // overshoot so that the average over time is close to `target_bitrate`.

  absl::optional<double> GetMediaRateUtilizationFactor(int64_t time_ms);

  void Reset();

 private:

  int64_t IdealFrameSizeBits() const;

  void LeakBits(int64_t time_ms);

  void CullOldUpdates(int64_t time_ms);

  // Updates provided buffer and checks if overuse ensues, returns

  // the calculated utilization factor for this frame.

  double HandleEncodedFrame(size_t frame_size_bits,

                            int64_t ideal_frame_size_bits,

                            int64_t time_ms,

                            int64_t* buffer_level_bits) const;

  const int64_t window_size_ms_;

  int64_t time_last_update_ms_;

  struct BitrateUpdate {

    BitrateUpdate(double network_utilization_factor,

                  double media_utilization_factor,

                  int64_t update_time_ms)

        : network_utilization_factor(network_utilization_factor),

          media_utilization_factor(media_utilization_factor),

          update_time_ms(update_time_ms) {}

    // The utilization factor based on strict network rate.

    double network_utilization_factor;

    // The utilization based on average media rate.

    double media_utilization_factor;

    int64_t update_time_ms;

};

  void UpdateHistograms();

  std::deque<BitrateUpdate> utilization_factors_;

  double sum_network_utilization_factors_;

  double sum_media_utilization_factors_;

  DataRate target_bitrate_;

  double target_framerate_fps_;

  int64_t network_buffer_level_bits_;

  int64_t media_buffer_level_bits_;

  VideoCodecType codec_;

  bool is_screenshare_;

  int64_t frame_count_;

  int64_t sum_diff_kbps_squared_;

  int64_t sum_overshoot_percent_;

};

}  // namespace webrtc

#endif  // VIDEO_ENCODER_OVERSHOOT_DETECTOR_H_