A bunch of linux tivo hackers managed to find a way to digitally extract the mpegs from their tivos with some special software and a network card in the tivo. I don't have the url, but if you search on slashdot I'm sure you can find it.
Now this is much harder than the digital to analog converter way, but if you have some experience with linux, nothing to do some weekend, and feel like voiding your warranty, it might be worth a shot.