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Diffstat (limited to 'Source/WebCore/platform/audio/SincResampler.h')
-rw-r--r-- | Source/WebCore/platform/audio/SincResampler.h | 79 |
1 files changed, 79 insertions, 0 deletions
diff --git a/Source/WebCore/platform/audio/SincResampler.h b/Source/WebCore/platform/audio/SincResampler.h new file mode 100644 index 0000000..92adb95 --- /dev/null +++ b/Source/WebCore/platform/audio/SincResampler.h @@ -0,0 +1,79 @@ +/* + * Copyright (C) 2011 Google Inc. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of + * its contributors may be used to endorse or promote products derived + * from this software without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY + * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED + * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE + * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY + * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES + * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; + * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#ifndef SincResampler_h +#define SincResampler_h + +#include "AudioArray.h" + +namespace WebCore { + +// SincResampler is a high-quality sample-rate converter. + +class SincResampler { +public: + // scaleFactor == sourceSampleRate / destinationSampleRate + // kernelSize can be adjusted for quality (higher is better) + // numberOfKernelOffsets is used for interpolation and is the number of sub-sample kernel shifts. + SincResampler(double scaleFactor, unsigned kernelSize = 64, unsigned numberOfKernelOffsets = 32); + + // Processes numberOfSourceFrames from source to produce numberOfSourceFrames / scaleFactor frames in destination. + void process(float* source, float* destination, unsigned numberOfSourceFrames); + + // FIXME: we can add a process() method which takes an input source callback function for streaming applications + // where the entire input buffer is not all available. + +protected: + void initializeKernel(); + void consumeSource(float* buffer, unsigned numberOfSourceFrames); + + double m_scaleFactor; + unsigned m_kernelSize; + unsigned m_numberOfKernelOffsets; + + // m_kernelStorage has m_numberOfKernelOffsets kernels back-to-back, each of size m_kernelSize. + // The kernel offsets are sub-sample shifts of a windowed sinc() shifted from 0.0 to 1.0 sample. + AudioFloatArray m_kernelStorage; + + // m_virtualSourceIndex is an index on the source input buffer with sub-sample precision. + // It must be double precision to avoid drift. + double m_virtualSourceIndex; + + // This is the number of destination frames we generate per processing pass on the buffer. + unsigned m_blockSize; + + // Source is copied into this buffer for each processing pass. + AudioFloatArray m_inputBuffer; + + float* m_source; + unsigned m_sourceFramesAvailable; +}; + +} // namespace WebCore + +#endif // SincResampler_h |