corruption_classifier.h

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/*

 * Copyright 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_CORRUPTION_DETECTION_CORRUPTION_CLASSIFIER_H_

#define VIDEO_CORRUPTION_DETECTION_CORRUPTION_CLASSIFIER_H_

#include <variant>

#include "api/array_view.h"

#include "video/corruption_detection/halton_frame_sampler.h"

namespace webrtc {

// Based on the given filtered samples to `CalculateCorruptionProbability` this

// class calculates a probability to indicate whether the frame is corrupted.

// The classification is done either by scaling the loss to the interval of [0,

// 1] using a simple `scale_factor` or by applying a logistic function to the

// loss. The logistic function is constructed based on `growth_rate` and

// `midpoint`, to the score between the original and the compressed frames'

// samples. This score is calculated using `GetScore`.

//

// TODO: bugs.webrtc.org/358039777 - Remove one of the constructors based on

// which mapping function works best in practice.

class CorruptionClassifier {

 public:

  // Calculates the corruption probability using a simple scale factor.

  explicit CorruptionClassifier(float scale_factor);

  // Calculates the corruption probability using a logistic function.

  CorruptionClassifier(float growth_rate, float midpoint);

  ~CorruptionClassifier() = default;

  // This function calculates and returns the probability (in the interval [0,

  // 1] that a frame is corrupted. The probability is determined either by

  // scaling the loss to the interval of [0, 1] using a simple `scale_factor`

  // or by applying a logistic function to the loss. The method is chosen

  // depending on the used constructor.

  double CalculateCorruptionProbability(

      rtc::ArrayView<const FilteredSample> filtered_original_samples,

      rtc::ArrayView<const FilteredSample> filtered_compressed_samples,

      int luma_threshold,

      int chroma_threshold) const;

 private:

  struct ScalarConfig {

    float scale_factor;

};

  // Logistic function parameters. See

  // https://en.wikipedia.org/wiki/Logistic_function.

  struct LogisticFunctionConfig {

    float growth_rate;

    float midpoint;

};

  // Returns the non-normalized score between the original and the compressed

  // frames' samples.

  double GetScore(

      rtc::ArrayView<const FilteredSample> filtered_original_samples,

      rtc::ArrayView<const FilteredSample> filtered_compressed_samples,

      int luma_threshold,

      int chroma_threshold) const;

  const std::variant<ScalarConfig, LogisticFunctionConfig> config_;

};

}  // namespace webrtc

#endif  // VIDEO_CORRUPTION_DETECTION_CORRUPTION_CLASSIFIER_H_