q: where to store jump label information?
q: what about unresolved jumps due to labels unknown at the time of compilation?
a to both:  until TOC generation, do not bother generating IFO files.  instead only generate intermediate info.  -- but then would that require the same version of dvdauthor for everything?  you couldn't author a titleset and then expect to use it many months later

q: how to handle button identification?  hard to label buttons when drawing in the gimp

<dvd workdir="/tmp">
	<titleset>
		<menus>
			<audio ac3/mp2/pcm/dts lang="en/de" .../>
			<video ntsc/pal resolution="704x480" .../>
			<pgc entry="foo" label="bar" [palette="foo.rgb"]>
				<pre>
				  g3=5;
				</pre>
				<post>
				  if(g3 ne 5) {
					exit;
				  }
				  jump bar;
				</post>
				<button num="x">
				  jump blahblah;
				</button>
				<vob file="foo.mpg" [nochapter] [chapters="x:y,y:z"] [stilltime="foo"]/>
			</pgc>
		</menus>
		<titles>
		</titles>
	</titleset>
	<toc>
		<fpc>
			jump bar;
		</fpc>
		<menus>
		</menus>
	</toc>
</dvd>

desired abilities:
	jump to any menu, title, chapter etc from any other point
	ability to set entry menu dependent on the 

DVD:
	pgcgroup -> menu
	list of titlesets

Titleset:
	(belongs to one dvd)
	pgcgroup -> menu
	pgcgroup -> title
	list of vob chunks

PGC Group:
	(belongs to one titleset or dvd)
	list of pgcs
	audio/subtitle/video configuration

PGC:
	(belongs to one pgcgroup)
	entry
	pre,post commands
	palette
	which audio/subtitle tracks are enabled
	list of cells
	     cell ptr
	     chapter entry?
	     discontinuity flag
	     seamless flag
	     stilltime flag

Vob chunk:
	input vob stream
	vob id
	list of cells
	(belongs to one titleset)

Cell:
	cell id
	(belongs to one vob chunk)
	start sector
	vobu information
	     start sector, length
	     video pts information?
	audio pts sector information