third_party/blink/renderer/modules/webaudio/realtime_analyser.h

/*
 * Copyright (C) 2010, Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1.  Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2.  Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 */

#ifndef THIRD_PARTY_BLINK_RENDERER_MODULES_WEBAUDIO_REALTIME_ANALYSER_H_
#define THIRD_PARTY_BLINK_RENDERER_MODULES_WEBAUDIO_REALTIME_ANALYSER_H_

#include <atomic>
#include <memory>

#include "third_party/blink/renderer/core/typed_arrays/dom_typed_array.h"
#include "third_party/blink/renderer/platform/audio/audio_array.h"
#include "third_party/blink/renderer/platform/audio/fft_frame.h"

namespace blink {

class AudioBus;

class RealtimeAnalyser final {
  DISALLOW_NEW();

 public:
  static constexpr double kDefaultSmoothingTimeConstant = 0.8;
  static constexpr double kDefaultMinDecibels = -100.0;
  static constexpr double kDefaultMaxDecibels = -30.0;

  static constexpr unsigned kDefaultFFTSize = 2048;
  // All FFT implementations are expected to handle power-of-two sizes
  // MinFFTSize <= size <= MaxFFTSize.
  static constexpr unsigned kMinFFTSize = 32;
  static constexpr unsigned kMaxFFTSize = 32768;
  static constexpr unsigned kInputBufferSize = kMaxFFTSize * 2;

  explicit RealtimeAnalyser(unsigned render_quantum_frames);

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

  uint32_t FftSize() const { return fft_size_; }
  bool SetFftSize(uint32_t);

  unsigned FrequencyBinCount() const { return fft_size_ / 2; }

  void SetMinDecibels(double k) { min_decibels_ = k; }
  double MinDecibels() const { return min_decibels_; }

  void SetMaxDecibels(double k) { max_decibels_ = k; }
  double MaxDecibels() const { return max_decibels_; }

  void SetSmoothingTimeConstant(double k) { smoothing_time_constant_ = k; }
  double SmoothingTimeConstant() const { return smoothing_time_constant_; }

  void GetFloatFrequencyData(DOMFloat32Array*, double);
  void GetByteFrequencyData(DOMUint8Array*, double);
  void GetFloatTimeDomainData(DOMFloat32Array*);
  void GetByteTimeDomainData(DOMUint8Array*);

  // The audio thread writes input data here.
  void WriteInput(AudioBus*, uint32_t frames_to_process);

 private:
  // The audio thread writes the input audio here.
  AudioFloatArray input_buffer_;
  std::atomic_uint write_index_{0};

  unsigned GetWriteIndex() const {
    return write_index_.load(std::memory_order_acquire);
  }
  void SetWriteIndex(unsigned new_index) {
    write_index_.store(new_index, std::memory_order_release);
  }

  // Input audio is downmixed to this bus before copying to m_inputBuffer.
  scoped_refptr<AudioBus> down_mix_bus_;

  uint32_t fft_size_;
  std::unique_ptr<FFTFrame> analysis_frame_;
  void DoFFTAnalysis();

  // Convert the contents of `magnitude_buffer_` to byte values, saving the
  // result in `destination`.
  void ConvertToByteData(DOMUint8Array* destination);

  // Convert `magnitude_buffer_` to dB, saving the result in `destination`
  void ConvertFloatToDb(DOMFloat32Array* destination);

  // doFFTAnalysis() stores the floating-point magnitude analysis data here.
  AudioFloatArray magnitude_buffer_;
  AudioFloatArray& MagnitudeBuffer() { return magnitude_buffer_; }

  // A value between 0 and 1 which averages the previous version of
  // m_magnitudeBuffer with the current analysis magnitude data.
  double smoothing_time_constant_;

  // The range used when converting when using getByteFrequencyData().
  double min_decibels_;
  double max_decibels_;

  // Time at which the FFT was last computed.
  double last_analysis_time_ = -1;
};

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_MODULES_WEBAUDIO_REALTIME_ANALYSER_H_