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/*
* 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
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* 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
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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/macros.h"
#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/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);
public:
// Note: this is destructive on the passed in AudioChannel.
// The length of channel must be a power of two.
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) {}
// 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:
std::unique_ptr<FFTFrame> fft_frame_;
float frame_delay_;
float sample_rate_;
DISALLOW_COPY_AND_ASSIGN(HRTFKernel);
};
typedef Vector<std::unique_ptr<HRTFKernel>> HRTFKernelList;
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_AUDIO_HRTF_KERNEL_H_