To play VCD\'s on the Dreamcast, you don\'t need a chip or anything. All you need is a disk with a small self-bootable program on it and the movie you wish you play. That\'s it. The program boots up, and gives you the VCD player interface.
I don\'t see where the process would be much different on the PS2. AFAIK, there is no hack for it to play VCD\'s tho. I\'m probably wrong since I haven\'t done too much looking up on the subject.. but I haven\'t run across any.