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#include "config.h"
30
31#if ENABLE(WEB_AUDIO)
32
33#include "UpSampler.h"
34
35#include <wtf/MathExtras.h>
36
37namespace WebCore {
38
39UpSampler::UpSampler(size_t inputBlockSize)
40    : m_inputBlockSize(inputBlockSize)
41    , m_kernel(DefaultKernelSize)
42    , m_convolver(inputBlockSize)
43    , m_tempBuffer(inputBlockSize)
44    , m_inputBuffer(inputBlockSize * 2)
45{
46    initializeKernel();
47}
48
49void UpSampler::initializeKernel()
50{
51    // Blackman window parameters.
52    double alpha = 0.16;
53    double a0 = 0.5 * (1.0 - alpha);
54    double a1 = 0.5;
55    double a2 = 0.5 * alpha;
56
57    int n = m_kernel.size();
58    int halfSize = n / 2;
59    double subsampleOffset = -0.5;
60
61    for (int i = 0; i < n; ++i) {
62        // Compute the sinc() with offset.
63        double s = piDouble * (i - halfSize - subsampleOffset);
64        double sinc = !s ? 1.0 : sin(s) / s;
65
66        // Compute Blackman window, matching the offset of the sinc().
67        double x = (i - subsampleOffset) / n;
68        double window = a0 - a1 * cos(2.0 * piDouble * x) + a2 * cos(4.0 * piDouble * x);
69
70        // Window the sinc() function.
71        m_kernel[i] = sinc * window;
72    }
73}
74
75void UpSampler::process(const float* sourceP, float* destP, size_t sourceFramesToProcess)
76{
77    bool isInputBlockSizeGood = sourceFramesToProcess == m_inputBlockSize;
78    ASSERT(isInputBlockSizeGood);
79    if (!isInputBlockSizeGood)
80        return;
81
82    bool isTempBufferGood = sourceFramesToProcess == m_tempBuffer.size();
83    ASSERT(isTempBufferGood);
84    if (!isTempBufferGood)
85        return;
86
87    bool isKernelGood = m_kernel.size() == DefaultKernelSize;
88    ASSERT(isKernelGood);
89    if (!isKernelGood)
90        return;
91
92    size_t halfSize = m_kernel.size() / 2;
93
94    // Copy source samples to 2nd half of input buffer.
95    bool isInputBufferGood = m_inputBuffer.size() == sourceFramesToProcess * 2 && halfSize <= sourceFramesToProcess;
96    ASSERT(isInputBufferGood);
97    if (!isInputBufferGood)
98        return;
99
100    float* inputP = m_inputBuffer.data() + sourceFramesToProcess;
101    memcpy(inputP, sourceP, sizeof(float) * sourceFramesToProcess);
102
103    // Copy even sample-frames 0,2,4,6... (delayed by the linear phase delay) directly into destP.
104    for (unsigned i = 0; i < sourceFramesToProcess; ++i)
105        destP[i * 2] = *((inputP - halfSize) + i);
106
107    // Compute odd sample-frames 1,3,5,7...
108    float* oddSamplesP = m_tempBuffer.data();
109    m_convolver.process(&m_kernel, sourceP, oddSamplesP, sourceFramesToProcess);
110
111    for (unsigned i = 0; i < sourceFramesToProcess; ++i)
112        destP[i * 2 + 1] = oddSamplesP[i];
113
114    // Copy 2nd half of input buffer to 1st half.
115    memcpy(m_inputBuffer.data(), inputP, sizeof(float) * sourceFramesToProcess);
116}
117
118void UpSampler::reset()
119{
120    m_convolver.reset();
121    m_inputBuffer.zero();
122}
123
124size_t UpSampler::latencyFrames() const
125{
126    // Divide by two since this is a linear phase kernel and the delay is at the center of the kernel.
127    return m_kernel.size() / 2;
128}
129
130} // namespace WebCore
131
132#endif // ENABLE(WEB_AUDIO)
133