once you have decoded VOB files (Not subject of these notes) or you recorded your own (which I do on a Magnavox DVD / VCR) they are huge mpeg1 files. This is just a note to self on how to convert to avi files, with much less gas. It produces a 350mb or so / hour of play time avi, which is the desirable archive for my recordings.
once you have identified each block of programming vob's cat them together into a single vob. There doesn't seem to be a problem with that. Other formats have to be called out in the ffmpeg or avconv command line, but prep for vob files is to just cat them into a bunch of files.
On and example file, here are the VOB files
cat VTS_01_*.VOB > videofile.vob
once you have your intermediate vob, convert it to an avi container as below.
avconv -i videofile.vob -f avi -c:v mpeg4 -b:v 800k -g 300 -bf 2 -c:a ac3 -b:a 128k videofile.avi
The resulting playback works with the bsplayer (open source codecs) and apple mac playback. It seems to have keyframe problems playing with windows media player. but in that case for my purposes, I don't care. I can use vlc anywhere there is windows.
Stack exchange posting with some more info
Ubuntu forum posting