A DVDplayer
-----------

1) set up a pipeline

 <draw pipeline schematics here>

2) set to playing

 - dvdnav reads the ifo file. A set of events are generated to configure
   various elements in the pipeline. These would include:
     - SPU colors
     - whatmore..

 - first the src will read the DVD menu. this will contain mpeg2 data
   and spu/nav info. after the menu is sent down the pipeline
   the nav decoder waits for input somehow. The pipeline keeps on 
   playing to animate the menus.

 - somehow a button is pressed on the menu: a method is triggered in
   the dvdnav plugin to tell it button X was pressed (event? app?).

 - dvdnav reacts and starts to stream other data.

 - nav packets in the stream indicate what can happen next.
   - update the menu
   - keep the menu
   - hide the menu
   - show the menu

 - pressing the hotkey to bring up the menu triggers a method in dvdnav
   which will send down nav info downstream to bring up the menu. 
   A background picture (I frame) is sent downstream too.

 - nav info can also happen while playing the movie. This can highlite 
   some buttons the user can press.
   
 - selecting a button triggers some color/compositing changes in SPU/NAVdec
   and an action on dvdnav.