1/*
2 * Copyright (C) 2013 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 UpSampler_h
30#define UpSampler_h
31
32#include "AudioArray.h"
33#include "DirectConvolver.h"
34
35namespace WebCore {
36
37// UpSampler up-samples the source stream by a factor of 2x.
38
39class UpSampler {
40 WTF_MAKE_FAST_ALLOCATED;
41public:
42 UpSampler(size_t inputBlockSize);
43
44 // The destination buffer |destP| is of size sourceFramesToProcess * 2.
45 void process(const float* sourceP, float* destP, size_t sourceFramesToProcess);
46
47 void reset();
48
49 // Latency based on the source sample-rate.
50 size_t latencyFrames() const;
51
52private:
53 enum { DefaultKernelSize = 128 };
54
55 size_t m_inputBlockSize;
56
57 // Computes ideal band-limited filter coefficients to sample in between each source sample-frame.
58 // This filter will be used to compute the odd sample-frames of the output.
59 void initializeKernel();
60 AudioFloatArray m_kernel;
61
62 // Computes the odd sample-frames of the output.
63 DirectConvolver m_convolver;
64
65 AudioFloatArray m_tempBuffer;
66
67 // Delay line for generating the even sample-frames of the output.
68 // The source samples are delayed exactly to match the linear phase delay of the FIR filter (convolution)
69 // used to generate the odd sample-frames of the output.
70 AudioFloatArray m_inputBuffer;
71};
72
73} // namespace WebCore
74
75#endif // UpSampler_h
76