quality_convergence_monitor.h

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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_QUALITY_CONVERGENCE_MONITOR_H_

#define VIDEO_QUALITY_CONVERGENCE_MONITOR_H_

#include <deque>

#include <memory>

#include "api/field_trials_view.h"

#include "api/video/video_codec_type.h"

namespace webrtc {

class QualityConvergenceMonitor {

 public:

  struct Parameters {

    // Static QP threshold. No history or even refresh-frame requirements to

    // determine that target quality is reached if the QP value is at or below

    // this threshold.

    int static_qp_threshold = 0;

    // Determines if the dynamic threshold should be used for refresh frames.

    bool dynamic_detection_enabled = false;

    // Window lengths of QP values to use when determining if refresh frames

    // have reached the target quality. The combined window length is

    // `past_window_length` + `recent_window_length`. The recent part of the

    // window contains the most recent samples. Once the recent buffer reaches

    // this length, new samples will pop the oldest samples in recent and move

    // them to the past buffer. The average of `QP_past` must be equal to or

    // less than the average of `QP_recent` to determine that target quality is

    // reached. See the implementation in `AddSample()`.

    size_t recent_window_length = 0;

    size_t past_window_length = 0;

    // During dynamic detection, the average of `QP_past` must be less than or

    // equal to this threshold to determine that target quality is reached.

    int dynamic_qp_threshold = 0;

};

  explicit QualityConvergenceMonitor(const Parameters& params);

  static std::unique_ptr<QualityConvergenceMonitor> Create(

      int static_qp_threshold,

      VideoCodecType codec,

      const FieldTrialsView& trials);

  // Add the supplied `qp` value to the detection window.

  // `is_refresh_frame` must only be `true` if the corresponding

  // video frame is a refresh frame that is used to improve the visual quality.

  void AddSample(int qp, bool is_refresh_frame);

  // Returns `true` if the algorithm has determined that the supplied QP values

  // have converged and reached the target quality.

  bool AtTargetQuality() const;

  // Used in tests to verify that default values and field trials are set

  // correctly.

  Parameters GetParametersForTesting() const { return params_; }

 private:

  const Parameters params_;

  bool at_target_quality_ = false;

  // Contains a window of QP values. New values are added at the back while old

  // values are popped from the front to maintain the configured window length.

  std::deque<int> qp_window_;

};

}  // namespace webrtc

#endif  // VIDEO_QUALITY_CONVERGENCE_MONITOR_H_