SampleToGroupBox.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.FullBox;

/**
 * This table can be used to find the group that a sample belongs to and the
 * associated description of that sample group. The table is compactly coded
 * with each entry giving the index of the first sample of a run of samples with
 * the same sample group descriptor. The sample group description ID is an index
 * that refers to a SampleGroupDescription box, which contains entries
 * describing the characteristics of each sample group.
 *
 * There may be multiple instances of this box if there is more than one sample
 * grouping for the samples in a track. Each instance of the SampleToGroup box
 * has a type code that distinguishes different sample groupings. Within a
 * track, there shall be at most one instance of this box with a particular
 * grouping type. The associated SampleGroupDescription shall indicate the same
 * value for the grouping type.
 */
public class SampleToGroupBox extends FullBox {

	private long groupingType;
	private long[] sampleCount, groupDescriptionIndex;

	public SampleToGroupBox() {
		super("Sample To Group Box");
	}

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

		groupingType = in.readBytes(4);
		final int entryCount = (int) in.readBytes(4);
		sampleCount = new long[entryCount];
		groupDescriptionIndex = new long[entryCount];

		for(int i = 0; i<entryCount; i++) {
			sampleCount[i] = in.readBytes(4);
			groupDescriptionIndex[i] = in.readBytes(4);
		}
	}

	/**
	 * The grouping type is an integer that identifies the type (i.e. criterion
	 * used to form the sample groups) of the sample grouping and links it to
	 * its sample group description table with the same value for grouping type.
	 * At most one occurrence of this box with the same value for 'grouping
	 * type' shall exist for a track.
	 */
	public long getGroupingType() {
		return groupingType;
	}

	/**
	 * The sample count is an integer that gives the number of consecutive
	 * samples with the same sample group descriptor for a specific entry. If
	 * the sum of the sample count in this box is less than the total sample
	 * count, then the reader should effectively extend it with an entry that
	 * associates the remaining samples with no group.
	 * It is an error for the total in this box to be greater than the sample
	 * count documented elsewhere, and the reader behaviour would then be
	 * undefined.
	 */
	public long[] getSampleCount() {
		return sampleCount;
	}

	/**
	 * The group description index is an integer that gives the index of the
	 * sample group entry which describes the samples in this group for a
	 * specific entry. The index ranges from 1 to the number of sample group
	 * entries in the SampleGroupDescriptionBox, or takes the value 0 to
	 * indicate that this sample is a member of no group of this type.
	 */
	public long[] getGroupDescriptionIndex() {
		return groupDescriptionIndex;
	}
}