code: public boolean isSyncCurrentPosition(int syncmode) throws BitstreamException
  	{
  		int read = readBytes(syncbuf, 0, 4);
  		int headerstring = ((syncbuf[0] << 24) & 0xFF000000) | ((syncbuf[1] << 16) & 0x00FF0000) | ((syncbuf[2] << 8) & 0x0000FF00) | ((syncbuf[3] << 0) & 0x000000FF);
  
  		try
  		{
  			source.unread(syncbuf, 0, read);
  		}
  		catch (IOException ex)
  		{
  		}
  
  		boolean sync = false;
  		switch (read)
  		{
  			case 0:
  				sync = true;
  				break;
  			case 4:
  				sync = isSyncMark(headerstring, syncmode, syncword);
  				break;
  		}
  
  		return sync;
  	}
docs: Determines if the next 4 bytes of the stream represent a
  frame header.