SubSampleInformationBox.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;

/**
 * The Sub-Sample Information box is designed to contain sub-sample information.
 * A sub-sample is a contiguous range of bytes of a sample. The specific
 * definition of a sub-sample shall be supplied for a given coding system (e.g.
 * for ISO/IEC 14496-10, Advanced Video Coding). In the absence of such a
 * specific definition, this box shall not be applied to samples using that
 * coding system.
 * The table is sparsely coded; the table identifies which samples have
 * sub-sample structure by recording the difference in sample-number between
 * each entry. The first entry in the table records the sample number of the
 * first sample having sub-sample information.
 *
 * @author in-somnia
 */
public class SubSampleInformationBox extends FullBox {

	private long[] sampleDelta;
	private long[][] subsampleSize;
	private int[][] subsamplePriority;
	private boolean[][] discardable;

	public SubSampleInformationBox() {
		super("Sub Sample Information Box");
	}

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

		final int len = (version==1) ? 4 : 2;
		final int entryCount = (int) in.readBytes(4);
		sampleDelta = new long[entryCount];
		subsampleSize = new long[entryCount][];
		subsamplePriority = new int[entryCount][];
		discardable = new boolean[entryCount][];

		int j, subsampleCount;
		for(int i = 0; i<entryCount; i++) {
			sampleDelta[i] = in.readBytes(4);
			subsampleCount = (int) in.readBytes(2);
			subsampleSize[i] = new long[subsampleCount];
			subsamplePriority[i] = new int[subsampleCount];
			discardable[i] = new boolean[subsampleCount];

			for(j = 0; j<subsampleCount; j++) {
				subsampleSize[i][j] = in.readBytes(len);
				subsamplePriority[i][j] = in.read();
				discardable[i][j] = (in.read()&1)==1;
				in.skipBytes(4); //reserved
			}
		}
	}

	/**
	 * The sample delta for each entry is an integer that specifies the sample 
	 * number of the sample having sub-sample structure. It is coded as the 
	 * difference between the desired sample number, and the sample number
	 * indicated in the previous entry. If the current entry is the first entry,
	 * the value indicates the sample number of the first sample having
	 * sub-sample information, that is, the value is the difference between the
	 * sample number and zero.
	 *
	 * @return the sample deltas for all entries
	 */
	public long[] getSampleDelta() {
		return sampleDelta;
	}

	/**
	 * The subsample size is an integer that specifies the size, in bytes, of a
	 * specific sub-sample in a specific entry.
	 *
	 * @return the sizes of all subsamples
	 */
	public long[][] getSubsampleSize() {
		return subsampleSize;
	}

	/**
	 * The subsample priority is an integer specifying the degradation priority
	 * for a specific sub-sample in a specific entry. Higher values indicate
	 * sub-samples which are important to, and have a greater impact on, the
	 * decoded quality.
	 *
	 * @return all subsample priorities
	 */
	public int[][] getSubsamplePriority() {
		return subsamplePriority;
	}

	/**
	 * If true, the sub-sample is required to decode the current sample, while
	 * false means the sub-sample is not required to decode the current sample 
	 * but may be used for enhancements, e.g., the sub-sample consists of
	 * supplemental enhancement information (SEI) messages.
	 *
	 * @return a list of flags indicating if a specific subsample is discardable
	 */
	public boolean[][] getDiscardable() {
		return discardable;
	}
}