1/*
2 * Copyright (C) 2011 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;
23 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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 SincResampler_h
30#define SincResampler_h
31
32#include "AudioArray.h"
33
34namespace WebCore {
35
36// SincResampler is a high-quality sample-rate converter.
37
38class SincResampler {
39public:
40    // scaleFactor == sourceSampleRate / destinationSampleRate
41    // kernelSize can be adjusted for quality (higher is better)
42    // numberOfKernelOffsets is used for interpolation and is the number of sub-sample kernel shifts.
43    SincResampler(double scaleFactor, unsigned kernelSize = 32, unsigned numberOfKernelOffsets = 32);
44
45    // Processes numberOfSourceFrames from source to produce numberOfSourceFrames / scaleFactor frames in destination.
46    void process(float* source, float* destination, unsigned numberOfSourceFrames);
47
48    // FIXME: we can add a process() method which takes an input source callback function for streaming applications
49    // where the entire input buffer is not all available.
50
51protected:
52    void initializeKernel();
53    void consumeSource(float* buffer, unsigned numberOfSourceFrames);
54
55    double m_scaleFactor;
56    unsigned m_kernelSize;
57    unsigned m_numberOfKernelOffsets;
58
59    // m_kernelStorage has m_numberOfKernelOffsets kernels back-to-back, each of size m_kernelSize.
60    // The kernel offsets are sub-sample shifts of a windowed sinc() shifted from 0.0 to 1.0 sample.
61    AudioFloatArray m_kernelStorage;
62
63    // m_virtualSourceIndex is an index on the source input buffer with sub-sample precision.
64    // It must be double precision to avoid drift.
65    double m_virtualSourceIndex;
66
67    // This is the number of destination frames we generate per processing pass on the buffer.
68    unsigned m_blockSize;
69
70    // Source is copied into this buffer for each processing pass.
71    AudioFloatArray m_inputBuffer;
72
73    float* m_source;
74    unsigned m_sourceFramesAvailable;
75};
76
77} // namespace WebCore
78
79#endif // SincResampler_h
80