/*
 * Copyright (C) 2010 Google Inc. All rights reserved.
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 * 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.
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 *     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
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#ifndef HRTFKernel_h
#define HRTFKernel_h

#include "FFTFrame.h"
#include <wtf/OwnPtr.h>
#include <wtf/PassOwnPtr.h>
#include <wtf/PassRefPtr.h>
#include <wtf/RefCounted.h>
#include <wtf/RefPtr.h>
#include <wtf/Vector.h>

namespace WebCore {

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 HRTFKernel : public RefCounted<HRTFKernel> {
public:
    // Note: this is destructive on the passed in AudioChannel.
    // The length of channel must be a power of two.
    static PassRefPtr<HRTFKernel> create(AudioChannel* channel, size_t fftSize, double sampleRate, bool bassBoost)
    {
        return adoptRef(new HRTFKernel(channel, fftSize, sampleRate, bassBoost));
    }

    static PassRefPtr<HRTFKernel> create(PassOwnPtr<FFTFrame> fftFrame, double frameDelay, double sampleRate)
    {
        return adoptRef(new HRTFKernel(fftFrame, frameDelay, sampleRate));
    }

    // Given two HRTFKernels, and an interpolation factor x: 0 -> 1, returns an interpolated HRTFKernel.
    static PassRefPtr<HRTFKernel> createInterpolatedKernel(HRTFKernel* kernel1, HRTFKernel* kernel2, double x);
  
    FFTFrame* fftFrame() { return m_fftFrame.get(); }
    
    size_t fftSize() const { return m_fftFrame->fftSize(); }
    double frameDelay() const { return m_frameDelay; }

    double sampleRate() const { return m_sampleRate; }
    double nyquist() const { return 0.5 * sampleRate(); }

    // Converts back into impulse-response form.
    PassOwnPtr<AudioChannel> createImpulseResponse();

private:
    // Note: this is destructive on the passed in AudioChannel.
    HRTFKernel(AudioChannel* channel, size_t fftSize, double sampleRate, bool bassBoost);
    
    HRTFKernel(PassOwnPtr<FFTFrame> fftFrame, double frameDelay, double sampleRate)
        : m_fftFrame(fftFrame)
        , m_frameDelay(frameDelay)
        , m_sampleRate(sampleRate)
    {
    }
    
    OwnPtr<FFTFrame> m_fftFrame;
    double m_frameDelay;
    double m_sampleRate;
};

typedef Vector<RefPtr<HRTFKernel> > HRTFKernelList;

} // namespace WebCore

#endif // HRTFKernel_h
