ObjectDescriptor.java

/*
 *  Copyright (C) 2011 in-somnia
 * 
 *  This file is part of JAAD.
 * 
 *  JAAD is free software; you can redistribute it and/or modify it 
 *  under the terms of the GNU Lesser General Public License as 
 *  published by the Free Software Foundation; either version 3 of the 
 *  License, or (at your option) any later version.
 *
 *  JAAD is distributed in the hope that it will be useful, but WITHOUT 
 *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
 *  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General 
 *  Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library.
 *  If not, see <http://www.gnu.org/licenses/>.
 */
package net.sourceforge.jaad.mp4.od;

import net.sourceforge.jaad.mp4.MP4InputStream;
import java.io.IOException;

/**
 * The <code>ObjectDescriptor</code> consists of three different parts:
 *
 * The first part uniquely labels the <code>ObjectDescriptor</code> within its
 * name scope by means of an ID. Media objects in the scene description use this
 * ID to refer to their object descriptor. An optional URL String indicates that
 * the actual object descriptor resides at a remote location.
 *
 * The second part is a set of optional descriptors that support the inclusion
 * if future extensions as well as the transport of private data in a backward
 * compatible way.
 *
 * The third part consists of a list of <code>ESDescriptors</code>, each
 * providing parameters for a single elementary stream that relates to the media
 * object as well as an optional set of object content information descriptors.
 *
 * @author in-somnia
 */
public class ObjectDescriptor extends Descriptor {

	private int objectDescriptorID;
	private boolean urlPresent;
	private String url;

	void decode(MP4InputStream in) throws IOException {
		//10 bits objectDescriptorID, 1 bit url flag, 5 bits reserved
		final int x = (int) in.readBytes(2);
		objectDescriptorID = (x>>6)&0x3FF;
		urlPresent = ((x>>5)&1)==1;

		if(urlPresent) url = in.readString(size-2);

		readChildren(in);
	}

	/**
	 * The ID uniquely identifies this ObjectDescriptor within its name scope.
	 * It should be within 0 and 1023 exclusively. The value 0 is forbidden and
	 * the value 1023 is reserved.
	 *
	 * @return this ObjectDescriptor's ID
	 */
	public int getObjectDescriptorID() {
		return objectDescriptorID;
	}

	/**
	 * A flag that indicates the presence of a URL. If set, no profiles are
	 * present.
	 *
	 * @return true if a URL is present
	 */
	public boolean isURLPresent() {
		return urlPresent;
	}

	/**
	 * A URL String that shall point to another InitialObjectDescriptor. If no
	 * URL is present (if <code>isURLPresent()</code> returns false) this method
	 * returns null.
	 *
	 * @return a URL String or null if none is present
	 */
	public String getURL() {
		return url;
	}
}