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/*
 * @(#)MediaTimeBase.java	1.2 00/04/21
 *
 * Copyright 1996-1998 by Sun Microsystems, Inc.,
 * 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
 * All rights reserved.
 *
 * This software is the confidential and proprietary information
 * of Sun Microsystems, Inc. ("Confidential Information").  You
 * shall not disclose such Confidential Information and shall use
 * it only in accordance with the terms of the license agreement
 * you entered into with Sun.
 */

package com.sun.tv.media;

import javax.media.*;


/**
 * This is the abstract base class to create a time base
 * out of the media time of a component.
 * e.g., this can be used to generate a time base from an audio
 * device with reports time ticks as samples are played.
 * A TimeBase ticks even when the media has stopped.  This class
 * takes care of that by internally maintaining a system time base
 * that takes over when the media has ended.
 * A TimeBase needs to be monotonically increasing.  If the media
 * time is set or wrapped around, this class will takes care of that.
 */
abstract public class MediaTimeBase implements TimeBase {

    long origin = 0;
    long offset = 0;
    long time = 0;
    TimeBase systemTimeBase = null;

    public MediaTimeBase() {
        mediaStopped();
    }

    public Time getTime() {
        return new Time(getNanoseconds());
    }

    public synchronized long getNanoseconds() {
        long t;
        if (systemTimeBase != null)
    	    time = origin + systemTimeBase.getNanoseconds() - offset;
        else
    	    time = origin + getMediaTime() - offset;
        return time;
    }

    abstract public long getMediaTime();

    public synchronized void mediaStarted() {
	systemTimeBase = null;
	offset = getMediaTime();
        origin = time;
    }

    public synchronized void mediaStopped() {
	systemTimeBase = new SystemTimeBase();
	offset = systemTimeBase.getNanoseconds();
        origin = time;
    }

}