Oscillator.h   [plain text]

/*
 * Copyright (C) 2012, Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
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 *
 * 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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#ifndef Oscillator_h
#define Oscillator_h

#include "AudioBus.h"
#include "AudioParam.h"
#include "AudioScheduledSourceNode.h"
#include <wtf/OwnArrayPtr.h>
#include <wtf/PassRefPtr.h>
#include <wtf/RefPtr.h>
#include <wtf/Threading.h>

namespace WebCore {

class AudioContext;
class WaveTable;

// Oscillator is an audio generator of periodic waveforms.

class Oscillator : public AudioScheduledSourceNode {
public:
    // The waveform type.
    // These must be defined as in the .idl file.
    enum {
        SINE = 0,
        SQUARE = 1,
        SAWTOOTH = 2,
        TRIANGLE = 3,
        CUSTOM = 4
    };

    static PassRefPtr<Oscillator> create(AudioContext*, float sampleRate);

    virtual ~Oscillator();
    
    // AudioNode
    virtual void process(size_t framesToProcess);
    virtual void reset();

    unsigned short type() const { return m_type; }
    void setType(unsigned short);

    AudioParam* frequency() { return m_frequency.get(); }
    AudioParam* detune() { return m_detune.get(); }

    void setWaveTable(WaveTable*);

private:
    Oscillator(AudioContext*, float sampleRate);

    // Returns true if there are sample-accurate timeline parameter changes.
    bool calculateSampleAccuratePhaseIncrements(size_t framesToProcess);

    virtual bool propagatesSilence() const OVERRIDE;

    // One of the waveform types defined in the enum.
    unsigned short m_type;
    
    // Frequency value in Hertz.
    RefPtr<AudioParam> m_frequency;

    // Detune value (deviating from the frequency) in Cents.
    RefPtr<AudioParam> m_detune;

    bool m_firstRender;

    // m_virtualReadIndex is a sample-frame index into our buffer representing the current playback position.
    // Since it's floating-point, it has sub-sample accuracy.
    double m_virtualReadIndex;

    // This synchronizes process().
    mutable Mutex m_processLock;

    // Stores sample-accurate values calculated according to frequency and detune.
    AudioFloatArray m_phaseIncrements;
    AudioFloatArray m_detuneValues;
    
    RefPtr<WaveTable> m_waveTable;
};

} // namespace WebCore

#endif // Oscillator_h