If you want video and audio in for your MKIV, you have to buy the "tv tuner", you can find it on ebay easyli.
Or you can buy a tings like this : Interface Dvd Pour Bmw 5 E39, 3 E46, X5 E53 - Accessoire auto - Electronique auto - Achat et vente d'accessoires auto neufs et d'occasion sur PriceMinister