SampleDependencyTypeBox.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.boxes.impl;

import java.io.IOException;
import net.sourceforge.jaad.mp4.MP4InputStream;
import net.sourceforge.jaad.mp4.boxes.BoxTypes;
import net.sourceforge.jaad.mp4.boxes.FullBox;

/**
 * This optional table answers three questions about sample dependency:
 * <ul>
 * <li>does this sample depend on others (is it an I-picture)?</li>
 * <li>do no other samples depend on this one?</li>
 * <li>does this sample contain multiple (redundant) encodings of the data at
 * this time-instant (possibly with different dependencies)?</li>
 * </ul>
 *
 * In the absence of this table:
 * <ul>
 * <li>the sync sample table answers the first question; in most video codecs,
 * I-pictures are also sync points</li>
 * <li>the dependency of other samples on this one is unknown</li>
 * <li>the existence of redundant coding is unknown</li>
 * </ul>
 *
 * When performing 'trick' modes, such as fast-forward, it is possible to use
 * the first piece of information to locate independently decodable samples.
 * Similarly, when performing random access, it may be necessary to locate the
 * previous sync point or random access recovery point, and roll-forward from
 * the sync point or the pre-roll starting point of the random access recovery
 * point to the desired point. While rolling forward, samples on which no others
 * depend need not be retrieved or decoded.
 * The value of 'sample is depended on' is independent of the existence of
 * redundant codings. However, a redundant coding may have different
 * dependencies from the primary coding; if redundant codings are available, the
 * value of 'sample depends on' documents only the primary coding.
 *
 * A Sample Dependency Box may also occur in the Track Fragment Box.
 * 
 * @author in-somnia
 */
public class SampleDependencyTypeBox extends FullBox {

	private int[] sampleDependsOn, sampleIsDependedOn, sampleHasRedundancy;

	public SampleDependencyTypeBox() {
		super("Sample Dependency Type Box");
	}

	@Override
	public void decode(MP4InputStream in) throws IOException {
		super.decode(in);

		//get number of samples from SampleSizeBox
		long sampleCount = -1;
		if(parent.hasChild(BoxTypes.SAMPLE_SIZE_BOX)) sampleCount = ((SampleSizeBox) parent.getChild(BoxTypes.SAMPLE_SIZE_BOX)).getSampleCount();
		//TODO: uncomment when CompactSampleSizeBox is implemented
		//else if(parent.containsChild(BoxTypes.COMPACT_SAMPLE_SIZE_BOX)) sampleCount = ((CompactSampleSizeBox)parent.getChild(BoxTypes.SAMPLE_SIZE_BOX)).getSampleSize();
		sampleHasRedundancy = new int[(int) sampleCount];
		sampleIsDependedOn = new int[(int) sampleCount];
		sampleDependsOn = new int[(int) sampleCount];

		byte b;
		for(int i = 0; i<sampleCount; i++) {
			b = (byte) in.read();
			/* 2 bits reserved
			 * 2 bits sampleDependsOn
			 * 2 bits sampleIsDependedOn
			 * 2 bits sampleHasRedundancy
			 */
			sampleHasRedundancy[i] = b&3;
			sampleIsDependedOn[i] = (b>>2)&3;
			sampleDependsOn[i] = (b>>4)&3;
		}
	}

	/**
	 * The 'sample depends on' field takes one of the following four values:
	 * 0: the dependency of this sample is unknown
	 * 1: this sample does depend on others (not an I picture)
	 * 2: this sample does not depend on others (I picture)
	 * 3: reserved
	 *
	 * @return a list of 'sample depends on' values for all samples
	 */
	public int[] getSampleDependsOn() {
		return sampleDependsOn;
	}

	/**
	 * The 'sample is depended on' field takes one of the following four values:
	 * 0: the dependency of other samples on this sample is unknown
	 * 1: other samples may depend on this one (not disposable)
	 * 2: no other sample depends on this one (disposable)
	 * 3: reserved
	 *
	 * @return a list of 'sample is depended on' values for all samples
	 */
	public int[] getSampleIsDependedOn() {
		return sampleIsDependedOn;
	}

	/**
	 * The 'sample has redundancy' field takes one of the following four values:
	 * 0: it is unknown whether there is redundant coding in this sample
	 * 1: there is redundant coding in this sample
	 * 2: there is no redundant coding in this sample
	 * 3: reserved
	 * 
	 * @return a list of 'sample has redundancy' values for all samples
	 */
	public int[] getSampleHasRedundancy() {
		return sampleHasRedundancy;
	}
}