/*
* Copyright (C) 2013 Google Inc. All rights reserved.
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#ifndef DownSampler_h
#define DownSampler_h
#include "platform/audio/AudioArray.h"
#include "platform/audio/DirectConvolver.h"
namespace WebCore {
// DownSampler down-samples the source stream by a factor of 2x.
class PLATFORM_EXPORT DownSampler {
public:
DownSampler(size_t inputBlockSize);
// The destination buffer |destP| is of size sourceFramesToProcess / 2.
void process(const float* sourceP, float* destP, size_t sourceFramesToProcess);
void reset();
// Latency based on the destination sample-rate.
size_t latencyFrames() const;
private:
enum { DefaultKernelSize = 256 };
size_t m_inputBlockSize;
// Computes ideal band-limited half-band filter coefficients.
// In other words, filter out all frequencies higher than 0.25 * Nyquist.
void initializeKernel();
AudioFloatArray m_reducedKernel;
// Half-band filter.
DirectConvolver m_convolver;
AudioFloatArray m_tempBuffer;
// Used as delay-line (FIR filter history) for the input samples to account for the 0.5 term right in the middle of the kernel.
AudioFloatArray m_inputBuffer;
};
} // namespace WebCore
#endif // DownSampler_h