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 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#include "AudioSourceProvider.h"
34
35namespace WebCore {
36
37// SincResampler is a high-quality sample-rate converter.
38
39class SincResampler {
40public:
41 // scaleFactor == sourceSampleRate / destinationSampleRate
42 // kernelSize can be adjusted for quality (higher is better)
43 // numberOfKernelOffsets is used for interpolation and is the number of sub-sample kernel shifts.
44 SincResampler(double scaleFactor, unsigned kernelSize = 32, unsigned numberOfKernelOffsets = 32);
45
46 // Processes numberOfSourceFrames from source to produce numberOfSourceFrames / scaleFactor frames in destination.
47 void process(const float* source, float* destination, unsigned numberOfSourceFrames);
48
49 // Process with input source callback function for streaming applications.
50 void process(AudioSourceProvider*, float* destination, size_t framesToProcess);
51
52protected:
53 void initializeKernel();
54 void consumeSource(float* buffer, unsigned numberOfSourceFrames);
55
56 double m_scaleFactor;
57 unsigned m_kernelSize;
58 unsigned m_numberOfKernelOffsets;
59
60 // m_kernelStorage has m_numberOfKernelOffsets kernels back-to-back, each of size m_kernelSize.
61 // The kernel offsets are sub-sample shifts of a windowed sinc() shifted from 0.0 to 1.0 sample.
62 AudioFloatArray m_kernelStorage;
63
64 // m_virtualSourceIndex is an index on the source input buffer with sub-sample precision.
65 // It must be double precision to avoid drift.
66 double m_virtualSourceIndex;
67
68 // This is the number of destination frames we generate per processing pass on the buffer.
69 unsigned m_blockSize;
70
71 // Source is copied into this buffer for each processing pass.
72 AudioFloatArray m_inputBuffer;
73
74 const float* m_source;
75 unsigned m_sourceFramesAvailable;
76
77 // m_sourceProvider is used to provide the audio input stream to the resampler.
78 AudioSourceProvider* m_sourceProvider;
79
80 // The buffer is primed once at the very beginning of processing.
81 bool m_isBufferPrimed;
82};
83
84} // namespace WebCore
85
86#endif // SincResampler_h
87