Hmm, I get choppy playback....I even installed Mplayer, and same thing. Lol it took me a while to realize that the GUI is called "gmplayer" or something, I kept running the "mplayer" which was only the command line app.
Somehow I cannot enable DMA for my DVD drive, even if it supports UDMA2 (yes, UDMA2, not MultiwordDMA 2). If I use "hdparm -d1 /dev/dvd" it says it cannot be enabled. And yes I am doing it as root....