AudioGainNode.h revision cad810f21b803229eb11403f9209855525a25d57 
1/*
2 * Copyright (C) 2010, Google Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
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8 *    notice, this list of conditions and the following disclaimer.
9 * 2.  Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
15 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
16 * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
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23 */
24
25#ifndef AudioGainNode_h
26#define AudioGainNode_h
27
28#include "AudioGain.h"
29#include "AudioNode.h"
30#include <wtf/PassRefPtr.h>
31#include <wtf/Threading.h>
32
33namespace WebCore {
34
35class AudioContext;
36
37// AudioGainNode is an AudioNode with one input and one output which applies a gain (volume) change to the audio signal.
38// De-zippering (smoothing) is applied when the gain value is changed dynamically.
39
40class AudioGainNode : public AudioNode {
41public:
42    static PassRefPtr<AudioGainNode> create(AudioContext* context, double sampleRate)
43    {
44        return adoptRef(new AudioGainNode(context, sampleRate));
45    }
46
47    // AudioNode
48    virtual void process(size_t framesToProcess);
49    virtual void reset();
50
51    // Called in the main thread when the number of channels for the input may have changed.
52    virtual void checkNumberOfChannelsForInput(AudioNodeInput*);
53
54    // JavaScript interface
55    AudioGain* gain() { return m_gain.get(); }
56
57private:
58    AudioGainNode(AudioContext*, double sampleRate);
59
60    double m_lastGain; // for de-zippering
61    RefPtr<AudioGain> m_gain;
62
63    // This synchronizes live channel count changes which require an uninitialization / re-initialization.
64    // FIXME: this can go away when we implement optimization for mixing with gain directly in summing junction of AudioNodeInput.
65    mutable Mutex m_processLock;
66};
67
68} // namespace WebCore
69
70#endif // AudioGainNode_h
71