jpegrtpheader.java

FMJ（freedom media for java)是java视频开发的新选择

package net.sf.fmj.media.codec.video.jpeg;

import net.sf.fmj.utility.ByteUtils;

/**
 * 
 * A special header is added to each packet that immediately follows the
   RTP header:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Type specific |              Fragment Offset                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Type     |       Q       |     Width     |     Height    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 */
public class JpegRTPHeader
{
	/**
	 * In bytes.
	 */
	public static final int HEADER_SIZE = 8;	
	
	private final byte typeSpecific;
	private final int fragmentOffset;
	private final byte type;
	private final byte q;
	private final byte width;
	private final byte height;
	

	
	public JpegRTPHeader(final byte typeSpecific, final int fragmentOffset, final byte type, final byte q, final byte width, final byte height)
	{
		super();
		this.typeSpecific = typeSpecific;
		this.fragmentOffset = fragmentOffset;
		this.type = type;
		this.q = q;
		this.width = width;
		this.height = height;
	}
	
	public static JpegRTPHeader parse(byte[] data, int offset)
	{
		int i = offset;
		final byte typeSpecific = data[i++];
		int fragmentOffset = 0;
		for (int j = 0; j < 3; ++j)
		{	// big-endian.
			fragmentOffset <<= 8;
			fragmentOffset += data[i++] & 0xff;
		}	
		final byte type = data[i++];
		final byte q = data[i++];
		final byte width  = data[i++];
		final byte height  = data[i++];
		return new JpegRTPHeader(typeSpecific, fragmentOffset, type, q, width, height);
		
	
	}
	
	public byte[] toBytes()
	{
		byte[] data = new byte[HEADER_SIZE];
		int i = 0;
		data[i++] = typeSpecific;
		
		encode3ByteIntBE(fragmentOffset, data, i);
		i += 3;
		
		data[i++] = type;
		data[i++] = q;
		data[i++] = width;
		data[i++] = height;
		
		return data;
		
		
	}

	private static final int BITS_PER_BYTE = 8;

	private static final int MAX_SIGNED_BYTE = 127;
	private static final int MAX_BYTE = 0xFF;
	private static final int MAX_BYTE_PLUS1 = 256;

	
	private static void encode3ByteIntBE(int value, byte[] ba, int offset)	
	{
		int length = 3;
		
		for (int i = 0; i < length; ++i)
		{
			int byteValue = value & MAX_BYTE;
			if (byteValue > MAX_SIGNED_BYTE)
				byteValue = byteValue - MAX_BYTE_PLUS1;

			ba[offset + (length - i - 1)] = (byte) byteValue;
			
			value = value >> BITS_PER_BYTE;
		}		
	}	
	
	
	public int getWidthInPixels()
	{	return ByteUtils.uByteToInt(width) * 8;
	}
	public int getHeightInPixels()
	{	return ByteUtils.uByteToInt(height) * 8;
	}
	
	public int getWidthInBlocks()
	{	return ByteUtils.uByteToInt(width);
	}
	public int getHeightInBlocks()
	{	return ByteUtils.uByteToInt(height);
	}

	public int getFragmentOffset()
	{
		return fragmentOffset;
	}

	public int getQ()
	{
		return ByteUtils.uByteToInt(q);
	}

	public int getType()
	{
		return ByteUtils.uByteToInt(type);
	}

	public int getTypeSpecific()
	{
		return ByteUtils.uByteToInt(typeSpecific);
	}

	public String toString()
	{	return "typeSpecific=" + getTypeSpecific() + " fragmentOffset=" + getFragmentOffset() + " type=" + getType() + " q=" + getQ() + " w=" + getWidthInPixels() + " h=" + getHeightInPixels();
	}

	
	public boolean equals(Object o)
	{
		if (!(o instanceof JpegRTPHeader))
			return false;
		final JpegRTPHeader oCast = (JpegRTPHeader) o;
		return 
			this.typeSpecific == oCast.typeSpecific &&
			this.fragmentOffset == oCast.fragmentOffset &&
			this.type == oCast.type &&
			this.q == oCast.q &&
			this.width == oCast.width &&
			this.height == oCast.height;
			
	}
	
	public int hashCode()
	{
		return typeSpecific + fragmentOffset + type + q + width + height;
	}
}