third_party/blink/renderer/platform/audio/hrtf_kernel.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.
 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
 *     its contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE 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 OR ITS CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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 */

#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_AUDIO_HRTF_KERNEL_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_AUDIO_HRTF_KERNEL_H_

#include <memory>
#include <utility>

#include "base/memory/ptr_util.h"
#include "third_party/blink/renderer/platform/audio/fft_frame.h"
#include "third_party/blink/renderer/platform/wtf/allocator.h"
#include "third_party/blink/renderer/platform/wtf/noncopyable.h"
#include "third_party/blink/renderer/platform/wtf/vector.h"

namespace blink {

class AudioChannel;

// HRTF stands for Head-Related Transfer Function.
// HRTFKernel is a frequency-domain representation of an impulse-response used
// as part of the spatialized panning system.  For a given azimuth / elevation
// angle there will be one HRTFKernel for the left ear transfer function, and
// one for the right ear.  The leading delay (average group delay) for each
// impulse response is extracted:
//      m_fftFrame is the frequency-domain representation of the impulse
//      response with the delay removed
//      m_frameDelay is the leading delay of the original impulse response.
class PLATFORM_EXPORT HRTFKernel {
  USING_FAST_MALLOC(HRTFKernel);
  WTF_MAKE_NONCOPYABLE(HRTFKernel);

 public:
  // Note: this is destructive on the passed in AudioChannel.
  // The length of channel must be a power of two.
  static std::unique_ptr<HRTFKernel> Create(AudioChannel* channel,
                                            size_t fft_size,
                                            float sample_rate) {
    return base::WrapUnique(new HRTFKernel(channel, fft_size, sample_rate));
  }

  static std::unique_ptr<HRTFKernel> Create(std::unique_ptr<FFTFrame> fft_frame,
                                            float frame_delay,
                                            float sample_rate) {
    return base::WrapUnique(
        new HRTFKernel(std::move(fft_frame), frame_delay, sample_rate));
  }

  // Given two HRTFKernels, and an interpolation factor x: 0 -> 1, returns an
  // interpolated HRTFKernel.
  static std::unique_ptr<HRTFKernel>
  CreateInterpolatedKernel(HRTFKernel* kernel1, HRTFKernel* kernel2, float x);

  FFTFrame* FftFrame() { return fft_frame_.get(); }

  size_t FftSize() const { return fft_frame_->FftSize(); }
  float FrameDelay() const { return frame_delay_; }

  float SampleRate() const { return sample_rate_; }
  double Nyquist() const { return 0.5 * SampleRate(); }

  // Converts back into impulse-response form.
  std::unique_ptr<AudioChannel> CreateImpulseResponse();

 private:
  // Note: this is destructive on the passed in AudioChannel.
  HRTFKernel(AudioChannel*, size_t fft_size, float sample_rate);

  HRTFKernel(std::unique_ptr<FFTFrame> fft_frame,
             float frame_delay,
             float sample_rate)
      : fft_frame_(std::move(fft_frame)),
        frame_delay_(frame_delay),
        sample_rate_(sample_rate) {}

  std::unique_ptr<FFTFrame> fft_frame_;
  float frame_delay_;
  float sample_rate_;
};

typedef Vector<std::unique_ptr<HRTFKernel>> HRTFKernelList;

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_AUDIO_HRTF_KERNEL_H_