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 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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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 "FFTFrame.h"
33#include <memory>
34#include <wtf/RefCounted.h>
35#include <wtf/RefPtr.h>
36#include <wtf/Vector.h>
37
38namespace WebCore {
39
40class AudioChannel;
41
42// HRTF stands for Head-Related Transfer Function.
43// HRTFKernel is a frequency-domain representation of an impulse-response used as part of the spatialized panning system.
44// For a given azimuth / elevation angle there will be one HRTFKernel for the left ear transfer function, and one for the right ear.
45// The leading delay (average group delay) for each impulse response is extracted:
46// m_fftFrame is the frequency-domain representation of the impulse response with the delay removed
47// m_frameDelay is the leading delay of the original impulse response.
48class HRTFKernel : public RefCounted<HRTFKernel> {
49public:
50 // Note: this is destructive on the passed in AudioChannel.
51 // The length of channel must be a power of two.
52 static Ref<HRTFKernel> create(AudioChannel* channel, size_t fftSize, float sampleRate)
53 {
54 return adoptRef(*new HRTFKernel(channel, fftSize, sampleRate));
55 }
56
57 static Ref<HRTFKernel> create(std::unique_ptr<FFTFrame> fftFrame, float frameDelay, float sampleRate)
58 {
59 return adoptRef(*new HRTFKernel(WTFMove(fftFrame), frameDelay, sampleRate));
60 }
61
62 // Given two HRTFKernels, and an interpolation factor x: 0 -> 1, returns an interpolated HRTFKernel.
63 static RefPtr<HRTFKernel> createInterpolatedKernel(HRTFKernel* kernel1, HRTFKernel* kernel2, float x);
64
65 FFTFrame* fftFrame() { return m_fftFrame.get(); }
66
67 size_t fftSize() const;
68 float frameDelay() const { return m_frameDelay; }
69
70 float sampleRate() const { return m_sampleRate; }
71 double nyquist() const { return 0.5 * sampleRate(); }
72
73 // Converts back into impulse-response form.
74 std::unique_ptr<AudioChannel> createImpulseResponse();
75
76private:
77 // Note: this is destructive on the passed in AudioChannel.
78 HRTFKernel(AudioChannel*, size_t fftSize, float sampleRate);
79
80 HRTFKernel(std::unique_ptr<FFTFrame> fftFrame, float frameDelay, float sampleRate)
81 : m_fftFrame(WTFMove(fftFrame))
82 , m_frameDelay(frameDelay)
83 , m_sampleRate(sampleRate)
84 {
85 }
86
87 std::unique_ptr<FFTFrame> m_fftFrame;
88 float m_frameDelay;
89 float m_sampleRate;
90};
91
92typedef Vector<RefPtr<HRTFKernel>> HRTFKernelList;
93
94} // namespace WebCore
95
96#endif // HRTFKernel_h
97