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Side by Side Diff: third_party/WebKit/Source/platform/audio/ffmpeg/FFTFrameFFMPEG.cpp

Issue 2384073002: reflow comments in platform/audio (Closed)
Patch Set: comments (heh!) Created 4 years, 2 months ago
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1 /* 1 /*
2 * Copyright (C) 2011 Google Inc. All rights reserved. 2 * Copyright (C) 2011 Google Inc. All rights reserved.
3 * 3 *
4 * Redistribution and use in source and binary forms, with or without 4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions 5 * modification, are permitted provided that the following conditions
6 * are met: 6 * are met:
7 * 7 *
8 * 1. Redistributions of source code must retain the above copyright 8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer. 9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright 10 * 2. Redistributions in binary form must reproduce the above copyright
(...skipping 25 matching lines...) Expand all
36 36
37 extern "C" { 37 extern "C" {
38 #include <libavcodec/avfft.h> 38 #include <libavcodec/avfft.h>
39 } 39 }
40 40
41 #include "wtf/MathExtras.h" 41 #include "wtf/MathExtras.h"
42 42
43 namespace blink { 43 namespace blink {
44 44
45 #if ENABLE(ASSERT) 45 #if ENABLE(ASSERT)
46 // Max FFT size for FFMPEG. WebAudio currently only uses FFTs up to size 15 (2^ 15 points). 46 // Max FFT size for FFMPEG. WebAudio currently only uses FFTs up to size 15
47 // (2^15 points).
47 const int kMaxFFTPow2Size = 16; 48 const int kMaxFFTPow2Size = 16;
48 #endif 49 #endif
49 50
50 // Normal constructor: allocates for a given fftSize. 51 // Normal constructor: allocates for a given fftSize.
51 FFTFrame::FFTFrame(unsigned fftSize) 52 FFTFrame::FFTFrame(unsigned fftSize)
52 : m_FFTSize(fftSize), 53 : m_FFTSize(fftSize),
53 m_log2FFTSize(static_cast<unsigned>(log2(fftSize))), 54 m_log2FFTSize(static_cast<unsigned>(log2(fftSize))),
54 m_realData(fftSize / 2), 55 m_realData(fftSize / 2),
55 m_imagData(fftSize / 2), 56 m_imagData(fftSize / 2),
56 m_forwardContext(nullptr), 57 m_forwardContext(nullptr),
(...skipping 48 matching lines...) Expand 10 before | Expand all | Expand 10 after
105 // Compute Forward transform. 106 // Compute Forward transform.
106 av_rdft_calc(m_forwardContext, p); 107 av_rdft_calc(m_forwardContext, p);
107 108
108 // De-interleave to separate real and complex arrays. 109 // De-interleave to separate real and complex arrays.
109 int len = m_FFTSize / 2; 110 int len = m_FFTSize / 2;
110 111
111 float* real = m_realData.data(); 112 float* real = m_realData.data();
112 float* imag = m_imagData.data(); 113 float* imag = m_imagData.data();
113 for (int i = 0; i < len; ++i) { 114 for (int i = 0; i < len; ++i) {
114 int baseComplexIndex = 2 * i; 115 int baseComplexIndex = 2 * i;
115 // m_realData[0] is the DC component and m_imagData[0] is the nyquist compon ent 116 // m_realData[0] is the DC component and m_imagData[0] is the nyquist
116 // since the interleaved complex data is packed. 117 // component since the interleaved complex data is packed.
117 real[i] = p[baseComplexIndex]; 118 real[i] = p[baseComplexIndex];
118 imag[i] = p[baseComplexIndex + 1]; 119 imag[i] = p[baseComplexIndex + 1];
119 } 120 }
120 } 121 }
121 122
122 void FFTFrame::doInverseFFT(float* data) { 123 void FFTFrame::doInverseFFT(float* data) {
123 // Prepare interleaved data. 124 // Prepare interleaved data.
124 float* interleavedData = getUpToDateComplexData(); 125 float* interleavedData = getUpToDateComplexData();
125 126
126 // Compute inverse transform. 127 // Compute inverse transform.
127 av_rdft_calc(m_inverseContext, interleavedData); 128 av_rdft_calc(m_inverseContext, interleavedData);
128 129
129 // Scale so that a forward then inverse FFT yields exactly the original data. For some reason 130 // Scale so that a forward then inverse FFT yields exactly the original data.
130 // av_rdft_calc above returns values that are half of what I expect. Hence mak e the scale factor 131 // For some reason av_rdft_calc above returns values that are half of what I
132 // expect. Hence make the scale factor
131 // twice as large to compensate for that. 133 // twice as large to compensate for that.
132 const float scale = 2.0 / m_FFTSize; 134 const float scale = 2.0 / m_FFTSize;
133 VectorMath::vsmul(interleavedData, 1, &scale, data, 1, m_FFTSize); 135 VectorMath::vsmul(interleavedData, 1, &scale, data, 1, m_FFTSize);
134 } 136 }
135 137
136 float* FFTFrame::getUpToDateComplexData() { 138 float* FFTFrame::getUpToDateComplexData() {
137 // FIXME: if we can't completely get rid of this method, SSE 139 // FIXME: if we can't completely get rid of this method, SSE
138 // optimization could be considered if it shows up hot on profiles. 140 // optimization could be considered if it shows up hot on profiles.
139 int len = m_FFTSize / 2; 141 int len = m_FFTSize / 2;
140 const float* real = m_realData.data(); 142 const float* real = m_realData.data();
141 const float* imag = m_imagData.data(); 143 const float* imag = m_imagData.data();
142 float* c = m_complexData.data(); 144 float* c = m_complexData.data();
143 for (int i = 0; i < len; ++i) { 145 for (int i = 0; i < len; ++i) {
144 int baseComplexIndex = 2 * i; 146 int baseComplexIndex = 2 * i;
145 c[baseComplexIndex] = real[i]; 147 c[baseComplexIndex] = real[i];
146 c[baseComplexIndex + 1] = imag[i]; 148 c[baseComplexIndex + 1] = imag[i];
147 } 149 }
148 return const_cast<float*>(m_complexData.data()); 150 return const_cast<float*>(m_complexData.data());
149 } 151 }
150 152
151 RDFTContext* FFTFrame::contextForSize(unsigned fftSize, int trans) { 153 RDFTContext* FFTFrame::contextForSize(unsigned fftSize, int trans) {
152 // FIXME: This is non-optimal. Ideally, we'd like to share the contexts for FF TFrames of the same size. 154 // FIXME: This is non-optimal. Ideally, we'd like to share the contexts for
153 // But FFmpeg's RDFT uses a scratch buffer inside the context and so they are not thread-safe. 155 // FFTFrames of the same size. But FFmpeg's RDFT uses a scratch buffer
154 // We could improve this by sharing the FFTFrames on a per-thread basis. 156 // inside the context and so they are not thread-safe. We could improve this
157 // by sharing the FFTFrames on a per-thread basis.
155 ASSERT(fftSize); 158 ASSERT(fftSize);
156 int pow2size = static_cast<int>(log2(fftSize)); 159 int pow2size = static_cast<int>(log2(fftSize));
157 ASSERT(pow2size < kMaxFFTPow2Size); 160 ASSERT(pow2size < kMaxFFTPow2Size);
158 161
159 RDFTContext* context = av_rdft_init(pow2size, (RDFTransformType)trans); 162 RDFTContext* context = av_rdft_init(pow2size, (RDFTransformType)trans);
160 return context; 163 return context;
161 } 164 }
162 165
163 } // namespace blink 166 } // namespace blink
164 167
165 #endif // USE(WEBAUDIO_FFMPEG) 168 #endif // USE(WEBAUDIO_FFMPEG)
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