/*
* Copyright (C) 2011 Google Inc. All rights reserved.
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* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
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* its contributors may be used to endorse or promote products derived
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*
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#ifndef SincResampler_h
#define SincResampler_h
#include "platform/PlatformExport.h"
#include "platform/audio/AudioArray.h"
#include "platform/audio/AudioSourceProvider.h"
namespace WebCore {
// SincResampler is a high-quality sample-rate converter.
class PLATFORM_EXPORT 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 = 32, unsigned numberOfKernelOffsets = 32);
// Processes numberOfSourceFrames from source to produce numberOfSourceFrames / scaleFactor frames in destination.
void process(const float* source, float* destination, unsigned numberOfSourceFrames);
// Process with input source callback function for streaming applications.
void process(AudioSourceProvider*, float* destination, size_t framesToProcess);
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;
const float* m_source;
unsigned m_sourceFramesAvailable;
// m_sourceProvider is used to provide the audio input stream to the resampler.
AudioSourceProvider* m_sourceProvider;
// The buffer is primed once at the very beginning of processing.
bool m_isBufferPrimed;
};
} // namespace WebCore
#endif // SincResampler_h