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 are
6 * met:
7 *
8 *     * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 *     * Redistributions in binary form must reproduce the above
11 * copyright notice, this list of conditions and the following disclaimer
12 * in the documentation and/or other materials provided with the
13 * distribution.
14 *     * Neither the name of Google Inc. nor the names of its
15 * contributors may be used to endorse or promote products derived from
16 * this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30
31#include "config.h"
32
33#if ENABLE(WEB_AUDIO)
34
35#include "platform/audio/UpSampler.h"
36
37#include "wtf/MathExtras.h"
38
39namespace blink {
40
41UpSampler::UpSampler(size_t inputBlockSize)
42    : m_inputBlockSize(inputBlockSize)
43    , m_kernel(DefaultKernelSize)
44    , m_convolver(inputBlockSize)
45    , m_tempBuffer(inputBlockSize)
46    , m_inputBuffer(inputBlockSize * 2)
47{
48    initializeKernel();
49}
50
51void UpSampler::initializeKernel()
52{
53    // Blackman window parameters.
54    double alpha = 0.16;
55    double a0 = 0.5 * (1.0 - alpha);
56    double a1 = 0.5;
57    double a2 = 0.5 * alpha;
58
59    int n = m_kernel.size();
60    int halfSize = n / 2;
61    double subsampleOffset = -0.5;
62
63    for (int i = 0; i < n; ++i) {
64        // Compute the sinc() with offset.
65        double s = piDouble * (i - halfSize - subsampleOffset);
66        double sinc = !s ? 1.0 : sin(s) / s;
67
68        // Compute Blackman window, matching the offset of the sinc().
69        double x = (i - subsampleOffset) / n;
70        double window = a0 - a1 * cos(twoPiDouble * x) + a2 * cos(twoPiDouble * 2.0 * x);
71
72        // Window the sinc() function.
73        m_kernel[i] = sinc * window;
74    }
75}
76
77void UpSampler::process(const float* sourceP, float* destP, size_t sourceFramesToProcess)
78{
79    bool isInputBlockSizeGood = sourceFramesToProcess == m_inputBlockSize;
80    ASSERT(isInputBlockSizeGood);
81    if (!isInputBlockSizeGood)
82        return;
83
84    bool isTempBufferGood = sourceFramesToProcess == m_tempBuffer.size();
85    ASSERT(isTempBufferGood);
86    if (!isTempBufferGood)
87        return;
88
89    bool isKernelGood = m_kernel.size() == DefaultKernelSize;
90    ASSERT(isKernelGood);
91    if (!isKernelGood)
92        return;
93
94    size_t halfSize = m_kernel.size() / 2;
95
96    // Copy source samples to 2nd half of input buffer.
97    bool isInputBufferGood = m_inputBuffer.size() == sourceFramesToProcess * 2 && halfSize <= sourceFramesToProcess;
98    ASSERT(isInputBufferGood);
99    if (!isInputBufferGood)
100        return;
101
102    float* inputP = m_inputBuffer.data() + sourceFramesToProcess;
103    memcpy(inputP, sourceP, sizeof(float) * sourceFramesToProcess);
104
105    // Copy even sample-frames 0,2,4,6... (delayed by the linear phase delay) directly into destP.
106    for (unsigned i = 0; i < sourceFramesToProcess; ++i)
107        destP[i * 2] = *((inputP - halfSize) + i);
108
109    // Compute odd sample-frames 1,3,5,7...
110    float* oddSamplesP = m_tempBuffer.data();
111    m_convolver.process(&m_kernel, sourceP, oddSamplesP, sourceFramesToProcess);
112
113    for (unsigned i = 0; i < sourceFramesToProcess; ++i)
114        destP[i * 2 + 1] = oddSamplesP[i];
115
116    // Copy 2nd half of input buffer to 1st half.
117    memcpy(m_inputBuffer.data(), inputP, sizeof(float) * sourceFramesToProcess);
118}
119
120void UpSampler::reset()
121{
122    m_convolver.reset();
123    m_inputBuffer.zero();
124}
125
126size_t UpSampler::latencyFrames() const
127{
128    // Divide by two since this is a linear phase kernel and the delay is at the center of the kernel.
129    return m_kernel.size() / 2;
130}
131
132} // namespace blink
133
134#endif // ENABLE(WEB_AUDIO)
135