JavaScriptAudioNode.h   [plain text]

/*
 * 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.
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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
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL APPLE INC. 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;
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#ifndef JavaScriptAudioNode_h
#define JavaScriptAudioNode_h

#include "ActiveDOMObject.h"
#include "AudioNode.h"
#include "EventListener.h"
#include "EventTarget.h"
#include <wtf/Forward.h>
#include <wtf/PassRefPtr.h>
#include <wtf/RefPtr.h>
#include <wtf/Vector.h>

namespace WebCore {

class AudioBuffer;
class AudioContext;
class AudioProcessingEvent;

// JavaScriptAudioNode is an AudioNode which allows for arbitrary synthesis or processing directly using JavaScript.
// The API allows for a variable number of inputs and outputs, although it must have at least one input or output.
// This basic implementation supports no more than one input and output.
// The "onaudioprocess" attribute is an event listener which will get called periodically with an AudioProcessingEvent which has
// AudioBuffers for each input and output.

class JavaScriptAudioNode : public AudioNode, public EventTarget {
public:
    // bufferSize must be one of the following values: 256, 512, 1024, 2048, 4096, 8192, 16384.
    // This value controls how frequently the onaudioprocess event handler is called and how many sample-frames need to be processed each call.
    // Lower numbers for bufferSize will result in a lower (better) latency. Higher numbers will be necessary to avoid audio breakup and glitches.
    // The value chosen must carefully balance between latency and audio quality.
    static PassRefPtr<JavaScriptAudioNode> create(AudioContext*, double sampleRate, size_t bufferSize, unsigned numberOfInputs = 1, unsigned numberOfOutputs = 1);

    virtual ~JavaScriptAudioNode();

    // AudioNode
    virtual void process(size_t framesToProcess);
    virtual void reset();
    virtual void initialize();
    virtual void uninitialize();

    // EventTarget
    virtual ScriptExecutionContext* scriptExecutionContext() const;
    virtual JavaScriptAudioNode* toJavaScriptAudioNode();
    virtual EventTargetData* eventTargetData() { return &m_eventTargetData; }
    virtual EventTargetData* ensureEventTargetData()  { return &m_eventTargetData; }

    size_t bufferSize() const { return m_bufferSize; }

    DEFINE_ATTRIBUTE_EVENT_LISTENER(audioprocess);

    // Reconcile ref/deref which are defined both in AudioNode and EventTarget.
    using AudioNode::ref;
    using AudioNode::deref;
    
private:
    JavaScriptAudioNode(AudioContext*, double sampleRate, size_t bufferSize, unsigned numberOfInputs, unsigned numberOfOutputs);

    static void fireProcessEventDispatch(void* userData);
    void fireProcessEvent();

    // Double buffering
    unsigned doubleBufferIndex() const { return m_doubleBufferIndex; }
    void swapBuffers() { m_doubleBufferIndex = 1 - m_doubleBufferIndex; }
    unsigned m_doubleBufferIndex;
    unsigned m_doubleBufferIndexForEvent;
    Vector<RefPtr<AudioBuffer> > m_inputBuffers;
    Vector<RefPtr<AudioBuffer> > m_outputBuffers;

    virtual void refEventTarget() { ref(); }
    virtual void derefEventTarget() { deref(); }
    EventTargetData m_eventTargetData;

    size_t m_bufferSize;
    unsigned m_bufferReadWriteIndex;
    volatile bool m_isRequestOutstanding;
};

} // namespace WebCore

#endif // JavaScriptAudioNode_h