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#ifndef HRTFKernel_h
#define HRTFKernel_h
#include "platform/audio/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 PLATFORM_EXPORT 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, float sampleRate)
{
return adoptRef(new HRTFKernel(channel, fftSize, sampleRate));
}
static PassRefPtr<HRTFKernel> create(PassOwnPtr<FFTFrame> fftFrame, float frameDelay, float 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, float x);
FFTFrame* fftFrame() { return m_fftFrame.get(); }
size_t fftSize() const { return m_fftFrame->fftSize(); }
float frameDelay() const { return m_frameDelay; }
float 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*, size_t fftSize, float sampleRate);
HRTFKernel(PassOwnPtr<FFTFrame> fftFrame, float frameDelay, float sampleRate)
: m_fftFrame(fftFrame)
, m_frameDelay(frameDelay)
, m_sampleRate(sampleRate)
{
}
OwnPtr<FFTFrame> m_fftFrame;
float m_frameDelay;
float m_sampleRate;
};
typedef Vector<RefPtr<HRTFKernel> > HRTFKernelList;
} // namespace WebCore
#endif // HRTFKernel_h