third_party/WebKit/Source/platform/audio/ffmpeg/FFTFrameFFMPEG.cpp

   1 /*
   2  * Copyright (C) 2011 Google Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
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   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  *
  14  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
  15  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  16  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  17  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
  18  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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  23  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 // FFTFrame implementation using FFmpeg's RDFT algorithm,
  27 // suitable for use on Windows and Linux.
  28
  29 #include "config.h"
  30
  31 #if ENABLE(WEB_AUDIO)
  32
  33 #if USE(WEBAUDIO_FFMPEG)
  34
  35 #include "platform/audio/FFTFrame.h"
  36
  37 #include "platform/audio/VectorMath.h"
  38
  39 extern "C" {
  40     #include <libavcodec/avfft.h>
  41 }
  42
  43 #include "wtf/MathExtras.h"
  44
  45 namespace blink {
  46
  47 #if ENABLE(ASSERT)
  48 const int kMaxFFTPow2Size = 24;
  49 #endif
  50
  51 // Normal constructor: allocates for a given fftSize.
  52 FFTFrame::FFTFrame(unsigned fftSize)
  53     : m_FFTSize(fftSize)
  54     , m_log2FFTSize(static_cast<unsigned>(log2(fftSize)))
  55     , m_realData(fftSize / 2)
  56     , m_imagData(fftSize / 2)
  57     , m_forwardContext(nullptr)
  58     , m_inverseContext(nullptr)
  59     , m_complexData(fftSize)
  60 {
  61     // We only allow power of two.
  62     ASSERT(1UL << m_log2FFTSize == m_FFTSize);
  63
  64     m_forwardContext = contextForSize(fftSize, DFT_R2C);
  65     m_inverseContext = contextForSize(fftSize, IDFT_C2R);
  66 }
  67
  68 // Creates a blank/empty frame (interpolate() must later be called).
  69 FFTFrame::FFTFrame()
  70     : m_FFTSize(0)
  71     , m_log2FFTSize(0)
  72     , m_forwardContext(nullptr)
  73     , m_inverseContext(nullptr)
  74 {
  75 }
  76
  77 // Copy constructor.
  78 FFTFrame::FFTFrame(const FFTFrame& frame)
  79     : m_FFTSize(frame.m_FFTSize)
  80     , m_log2FFTSize(frame.m_log2FFTSize)
  81     , m_realData(frame.m_FFTSize / 2)
  82     , m_imagData(frame.m_FFTSize / 2)
  83     , m_forwardContext(nullptr)
  84     , m_inverseContext(nullptr)
  85     , m_complexData(frame.m_FFTSize)
  86 {
  87     m_forwardContext = contextForSize(m_FFTSize, DFT_R2C);
  88     m_inverseContext = contextForSize(m_FFTSize, IDFT_C2R);
  89
  90     // Copy/setup frame data.
  91     unsigned nbytes = sizeof(float) * (m_FFTSize / 2);
  92     memcpy(realData(), frame.realData(), nbytes);
  93     memcpy(imagData(), frame.imagData(), nbytes);
  94 }
  95
  96 void FFTFrame::initialize()
  97 {
  98 }
  99
 100 void FFTFrame::cleanup()
 101 {
 102 }
 103
 104 FFTFrame::~FFTFrame()
 105 {
 106     av_rdft_end(m_forwardContext);
 107     av_rdft_end(m_inverseContext);
 108 }
 109
 110 void FFTFrame::doFFT(const float* data)
 111 {
 112     // Copy since processing is in-place.
 113     float* p = m_complexData.data();
 114     memcpy(p, data, sizeof(float) * m_FFTSize);
 115
 116     // Compute Forward transform.
 117     av_rdft_calc(m_forwardContext, p);
 118
 119     // De-interleave to separate real and complex arrays.
 120     int len = m_FFTSize / 2;
 121
 122     float* real = m_realData.data();
 123     float* imag = m_imagData.data();
 124     for (int i = 0; i < len; ++i) {
 125         int baseComplexIndex = 2 * i;
 126         // m_realData[0] is the DC component and m_imagData[0] is the nyquist component
 127         // since the interleaved complex data is packed.
 128         real[i] = p[baseComplexIndex];
 129         imag[i] = p[baseComplexIndex + 1];
 130     }
 131 }
 132
 133 void FFTFrame::doInverseFFT(float* data)
 134 {
 135     // Prepare interleaved data.
 136     float* interleavedData = getUpToDateComplexData();
 137
 138     // Compute inverse transform.
 139     av_rdft_calc(m_inverseContext, interleavedData);
 140
 141     // Scale so that a forward then inverse FFT yields exactly the original data. For some reason
 142     // av_rdft_calc above returns values that are half of what I expect. Hence make the scale factor
 143     // twice as large to compensate for that.
 144     const float scale = 2.0 / m_FFTSize;
 145     VectorMath::vsmul(interleavedData, 1, &scale, data, 1, m_FFTSize);
 146 }
 147
 148 float* FFTFrame::getUpToDateComplexData()
 149 {
 150     // FIXME: if we can't completely get rid of this method, SSE
 151     // optimization could be considered if it shows up hot on profiles.
 152     int len = m_FFTSize / 2;
 153     const float* real = m_realData.data();
 154     const float* imag = m_imagData.data();
 155     float* c = m_complexData.data();
 156     for (int i = 0; i < len; ++i) {
 157         int baseComplexIndex = 2 * i;
 158         c[baseComplexIndex] = real[i];
 159         c[baseComplexIndex + 1] = imag[i];
 160     }
 161     return const_cast<float*>(m_complexData.data());
 162 }
 163
 164 RDFTContext* FFTFrame::contextForSize(unsigned fftSize, int trans)
 165 {
 166     // FIXME: This is non-optimal. Ideally, we'd like to share the contexts for FFTFrames of the same size.
 167     // But FFmpeg's RDFT uses a scratch buffer inside the context and so they are not thread-safe.
 168     // We could improve this by sharing the FFTFrames on a per-thread basis.
 169     ASSERT(fftSize);
 170     int pow2size = static_cast<int>(log2(fftSize));
 171     ASSERT(pow2size < kMaxFFTPow2Size);
 172
 173     RDFTContext* context = av_rdft_init(pow2size, (RDFTransformType)trans);
 174     return context;
 175 }
 176
 177 } // namespace blink
 178
 179 #endif // USE(WEBAUDIO_FFMPEG)
 180
 181 #endif // ENABLE(WEB_AUDIO)