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Side by Side Diff: Source/core/platform/audio/UpSampler.cpp

Issue 15619003: Add support for WaveShaperNode.oversample (Closed) Base URL: svn://svn.chromium.org/blink/trunk
Patch Set: change TestExpectations in middle of file Created 7 years, 6 months ago
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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 "core/platform/audio/UpSampler.h"
36
37 #include "wtf/MathExtras.h"
38
39 namespace WebCore {
40
41 UpSampler::UpSampler(size_t inputBlockSize)
42 : m_inputBlockSize(inputBlockSize)
43 , m_kernel(DefaultKernelSize)
44 , m_tempBuffer(inputBlockSize)
45 , m_inputBuffer(inputBlockSize * 2)
46 , m_convolver(inputBlockSize)
47 {
48 initializeKernel();
49 }
50
51 void 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(2.0 * piDouble * x) + a2 * cos(4.0 * piDou ble * x);
71
72 // Window the sinc() function.
73 m_kernel[i] = sinc * window;
74 }
75 }
76
77 void UpSampler::process(const float* sourceP, float* destP, size_t sourceFramesT oProcess)
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) di rectly into destP.
106 for (unsigned i = 0; i < sourceFramesToProcess; ++i)
107 destP[i * 2] = inputP[i - halfSize];
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
120 void UpSampler::reset()
121 {
122 m_convolver.reset();
123 m_inputBuffer.zero();
124 }
125
126 size_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 WebCore
133
134 #endif // ENABLE(WEB_AUDIO)
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