Quicktime Choppy compared to VLC?

I've got some mp4 files here that are accompanied by DT4 sound files. For some reason, when I play these files with Quicktime, the video is pretty choppy. Playing with VLC, everything seems to run smoothly. Why is quicktime slow? I'd like to use iTunes to organize my movies and watch them with Quicktime but not if the 720P and 1080P movies look choppy

I've got a SG33G5 with a Q6600 at 2.7ghz, 4 GB of RAM and a X1950GT video card (my system is a hackintosh). Do I need a new video card or is there something I need to do with the settings?

Thanks for clearing things up for me, guys. Spacepower7, you're right, it is a DTS file, not a DT4 file.

I didn't know the CPU did everything. I always thought the video card helped processing these files. But you'd think a quad core running at 2.7ghz would do the trick. I'll have to upgrade the RAM and try to get a bit more overclock.

Anyway, I have tried various mp4 files and all mp4 files played through quicktime is choppy. But like I said, played through VLC, it works like a charm. It's a shame. I was really looking to use iTunes to organize my movies and converting all my mkv files over to mp4.

I'll come back and let you guys know how things work out. I'm downloading all the suggested files now.

Thanks!



Henry