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      1 /*
      2  * Copyright (C) 2010 Google Inc. All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  *
      8  * 1.  Redistributions of source code must retain the above copyright
      9  *     notice, this list of conditions and the following disclaimer.
     10  * 2.  Redistributions in binary form must reproduce the above copyright
     11  *     notice, this list of conditions and the following disclaimer in the
     12  *     documentation and/or other materials provided with the distribution.
     13  * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
     14  *     its contributors may be used to endorse or promote products derived
     15  *     from this software without specific prior written permission.
     16  *
     17  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
     18  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     19  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     20  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
     21  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
     22  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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     24  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 #ifndef HRTFKernel_h
     30 #define HRTFKernel_h
     31 
     32 #include "core/platform/audio/FFTFrame.h"
     33 #include "wtf/OwnPtr.h"
     34 #include "wtf/PassOwnPtr.h"
     35 #include "wtf/PassRefPtr.h"
     36 #include "wtf/RefCounted.h"
     37 #include "wtf/RefPtr.h"
     38 #include "wtf/Vector.h"
     39 
     40 namespace WebCore {
     41 
     42 class AudioChannel;
     43 
     44 // HRTF stands for Head-Related Transfer Function.
     45 // HRTFKernel is a frequency-domain representation of an impulse-response used as part of the spatialized panning system.
     46 // For a given azimuth / elevation angle there will be one HRTFKernel for the left ear transfer function, and one for the right ear.
     47 // The leading delay (average group delay) for each impulse response is extracted:
     48 //      m_fftFrame is the frequency-domain representation of the impulse response with the delay removed
     49 //      m_frameDelay is the leading delay of the original impulse response.
     50 class HRTFKernel : public RefCounted<HRTFKernel> {
     51 public:
     52     // Note: this is destructive on the passed in AudioChannel.
     53     // The length of channel must be a power of two.
     54     static PassRefPtr<HRTFKernel> create(AudioChannel* channel, size_t fftSize, float sampleRate)
     55     {
     56         return adoptRef(new HRTFKernel(channel, fftSize, sampleRate));
     57     }
     58 
     59     static PassRefPtr<HRTFKernel> create(PassOwnPtr<FFTFrame> fftFrame, float frameDelay, float sampleRate)
     60     {
     61         return adoptRef(new HRTFKernel(fftFrame, frameDelay, sampleRate));
     62     }
     63 
     64     // Given two HRTFKernels, and an interpolation factor x: 0 -> 1, returns an interpolated HRTFKernel.
     65     static PassRefPtr<HRTFKernel> createInterpolatedKernel(HRTFKernel* kernel1, HRTFKernel* kernel2, float x);
     66 
     67     FFTFrame* fftFrame() { return m_fftFrame.get(); }
     68 
     69     size_t fftSize() const { return m_fftFrame->fftSize(); }
     70     float frameDelay() const { return m_frameDelay; }
     71 
     72     float sampleRate() const { return m_sampleRate; }
     73     double nyquist() const { return 0.5 * sampleRate(); }
     74 
     75     // Converts back into impulse-response form.
     76     PassOwnPtr<AudioChannel> createImpulseResponse();
     77 
     78 private:
     79     // Note: this is destructive on the passed in AudioChannel.
     80     HRTFKernel(AudioChannel*, size_t fftSize, float sampleRate);
     81 
     82     HRTFKernel(PassOwnPtr<FFTFrame> fftFrame, float frameDelay, float sampleRate)
     83         : m_fftFrame(fftFrame)
     84         , m_frameDelay(frameDelay)
     85         , m_sampleRate(sampleRate)
     86     {
     87     }
     88 
     89     OwnPtr<FFTFrame> m_fftFrame;
     90     float m_frameDelay;
     91     float m_sampleRate;
     92 };
     93 
     94 typedef Vector<RefPtr<HRTFKernel> > HRTFKernelList;
     95 
     96 } // namespace WebCore
     97 
     98 #endif // HRTFKernel_h
     99