Source/WebCore/webaudio/AudioGainNode.h

/*
 * Copyright (C) 2010, Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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 * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
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#ifndef AudioGainNode_h
#define AudioGainNode_h

#include "AudioGain.h"
#include "AudioNode.h"
#include <wtf/PassRefPtr.h>
#include <wtf/Threading.h>

namespace WebCore {

class AudioContext;
    
// AudioGainNode is an AudioNode with one input and one output which applies a gain (volume) change to the audio signal.
// De-zippering (smoothing) is applied when the gain value is changed dynamically.

class AudioGainNode : public AudioNode {
public:
    static PassRefPtr<AudioGainNode> create(AudioContext* context, double sampleRate)
    {
        return adoptRef(new AudioGainNode(context, sampleRate));      
    }
    
    // AudioNode
    virtual void process(size_t framesToProcess);
    virtual void reset();

    // Called in the main thread when the number of channels for the input may have changed.
    virtual void checkNumberOfChannelsForInput(AudioNodeInput*);

    // JavaScript interface
    AudioGain* gain() { return m_gain.get(); }                                   
    
private:
    AudioGainNode(AudioContext*, double sampleRate);

    double m_lastGain; // for de-zippering
    RefPtr<AudioGain> m_gain;

    // This synchronizes live channel count changes which require an uninitialization / re-initialization.
    // FIXME: this can go away when we implement optimization for mixing with gain directly in summing junction of AudioNodeInput.
    mutable Mutex m_processLock;
};

} // namespace WebCore

#endif // AudioGainNode_h