clipping_predictor.h

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/*

 *  Copyright (c) 2021 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 MODULES_AUDIO_PROCESSING_AGC2_CLIPPING_PREDICTOR_H_

#define MODULES_AUDIO_PROCESSING_AGC2_CLIPPING_PREDICTOR_H_

#include <memory>

#include <vector>

#include "absl/types/optional.h"

#include "api/audio/audio_processing.h"

#include "modules/audio_processing/include/audio_frame_view.h"

namespace webrtc {

// Frame-wise clipping prediction and clipped level step estimation. Analyzes

// 10 ms multi-channel frames and estimates an analog mic level decrease step

// to possibly avoid clipping when predicted. `Analyze()` and

// `EstimateClippedLevelStep()` can be called in any order.

class ClippingPredictor {

 public:

  virtual ~ClippingPredictor() = default;

  virtual void Reset() = 0;

  // Analyzes a 10 ms multi-channel audio frame.

  virtual void Analyze(const AudioFrameView<const float>& frame) = 0;

  // Predicts if clipping is going to occur for the specified `channel` in the

  // near-future and, if so, it returns a recommended analog mic level decrease

  // step. Returns absl::nullopt if clipping is not predicted.

  // `level` is the current analog mic level, `default_step` is the amount the

  // mic level is lowered by the analog controller with every clipping event and

  // `min_mic_level` and `max_mic_level` is the range of allowed analog mic

  // levels.

  virtual absl::optional<int> EstimateClippedLevelStep(

      int channel,

      int level,

      int default_step,

      int min_mic_level,

      int max_mic_level) const = 0;

};

// Creates a ClippingPredictor based on the provided `config`. When enabled,

// the following must hold for `config`:

// `window_length < reference_window_length + reference_window_delay`.

// Returns `nullptr` if `config.enabled` is false.

std::unique_ptr<ClippingPredictor> CreateClippingPredictor(

    int num_channels,

    const AudioProcessing::Config::GainController1::AnalogGainController::

        ClippingPredictor& config);

}  // namespace webrtc

#endif  // MODULES_AUDIO_PROCESSING_AGC2_CLIPPING_PREDICTOR_H_