Source/WebCore/platform/audio/MultiChannelResampler.h

/*
 * Copyright (C) 2011 Google Inc. All rights reserved.
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 *
 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
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#ifndef MultiChannelResampler_h
#define MultiChannelResampler_h

#include "AudioArray.h"
#include <memory>
#include <wtf/Function.h>
#include <wtf/Vector.h>

namespace WebCore {

class AudioBus;
class SincResampler;

class MultiChannelResampler final {
    WTF_MAKE_FAST_ALLOCATED;
public:   
    // requestFrames constrols the size of the buffer in frames when provideInput is called.
    MultiChannelResampler(double scaleFactor, unsigned numberOfChannels, unsigned requestFrames, Function<void(AudioBus*, size_t framesToProcess)>&& provideInput);
    ~MultiChannelResampler();

    void process(AudioBus* destination, size_t framesToProcess);

private:
    void provideInputForChannel(float* buffer, size_t framesToProcess, unsigned channelIndex);

    // FIXME: the mac port can have a more highly optimized implementation based on CoreAudio
    // instead of SincResampler. For now the default implementation will be used on all ports.
    // https://bugs.webkit.org/show_bug.cgi?id=75118
    
    // Each channel will be resampled using a high-quality SincResampler.
    Vector<std::unique_ptr<SincResampler>> m_kernels;
    
    unsigned m_numberOfChannels;
    size_t m_outputFramesReady { 0 };
    Function<void(AudioBus*, size_t framesToProcess)> m_provideInput;
    RefPtr<AudioBus> m_multiChannelBus;
    Vector<std::unique_ptr<AudioFloatArray>> m_channelsMemory;
};

} // namespace WebCore

#endif // MultiChannelResampler_h