capture_levels_adjuster.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_CAPTURE_LEVELS_ADJUSTER_CAPTURE_LEVELS_ADJUSTER_H_

#define MODULES_AUDIO_PROCESSING_CAPTURE_LEVELS_ADJUSTER_CAPTURE_LEVELS_ADJUSTER_H_

#include <stddef.h>

#include "modules/audio_processing/audio_buffer.h"

#include "modules/audio_processing/capture_levels_adjuster/audio_samples_scaler.h"

namespace webrtc {

// Adjusts the level of the capture signal before and after all capture-side

// processing is done using a combination of explicitly specified gains

// and an emulated analog gain functionality where a specified analog level

// results in an additional gain. The pre-adjustment is achieved by combining

// the gain value `pre_gain` and the level `emulated_analog_mic_gain_level` to

// form a combined gain of `pre_gain`*`emulated_analog_mic_gain_level`/255 which

// is multiplied to each sample. The intention of the

// `emulated_analog_mic_gain_level` is to be controlled by the analog AGC

// functionality and to produce an emulated analog mic gain equal to

// `emulated_analog_mic_gain_level`/255. The post level adjustment is achieved

// by multiplying each sample with the value of `post_gain`. Any changes in the

// gains take are done smoothly over one frame and the scaled samples are

// clamped to fit into the allowed S16 sample range.

class CaptureLevelsAdjuster {

 public:

  // C-tor. The values for the level and the gains must fulfill

  // 0 <= emulated_analog_mic_gain_level <= 255.

  // 0.f <= pre_gain.

  // 0.f <= post_gain.

  CaptureLevelsAdjuster(bool emulated_analog_mic_gain_enabled,

                        int emulated_analog_mic_gain_level,

                        float pre_gain,

                        float post_gain);

  CaptureLevelsAdjuster(const CaptureLevelsAdjuster&) = delete;

  CaptureLevelsAdjuster& operator=(const CaptureLevelsAdjuster&) = delete;

  // Adjusts the level of the signal. This should be called before any of the

  // other processing is performed.

  void ApplyPreLevelAdjustment(AudioBuffer& audio_buffer);

  // Adjusts the level of the signal. This should be called after all of the

  // other processing have been performed.

  void ApplyPostLevelAdjustment(AudioBuffer& audio_buffer);

  // Sets the gain to apply to each sample before any of the other processing is

  // performed.

  void SetPreGain(float pre_gain);

  // Returns the total pre-adjustment gain applied, comprising both the pre_gain

  // as well as the gain from the emulated analog mic, to each sample before any

  // of the other processing is performed.

  float GetPreAdjustmentGain() const { return pre_adjustment_gain_; }

  // Sets the gain to apply to each sample after all of the other processing

  // have been performed.

  void SetPostGain(float post_gain);

  // Sets the analog gain level to use for the emulated analog gain.

  // `level` must be in the range [0...255].

  void SetAnalogMicGainLevel(int level);

  // Returns the current analog gain level used for the emulated analog gain.

  int GetAnalogMicGainLevel() const { return emulated_analog_mic_gain_level_; }

 private:

  // Updates the value of `pre_adjustment_gain_` based on the supplied values

  // for `pre_gain` and `emulated_analog_mic_gain_level_`.

  void UpdatePreAdjustmentGain();

  const bool emulated_analog_mic_gain_enabled_;

  int emulated_analog_mic_gain_level_;

  float pre_gain_;

  float pre_adjustment_gain_;

  AudioSamplesScaler pre_scaler_;

  AudioSamplesScaler post_scaler_;

};

}  // namespace webrtc

#endif  // MODULES_AUDIO_PROCESSING_CAPTURE_LEVELS_ADJUSTER_CAPTURE_LEVELS_ADJUSTER_H_