DTS vs. AC3

whats the difference in these 2??

Can you use only one or the other, or do you need both??

Different ways of doing 5.1 or greater suround sound. I think DTS sounds better but they are both pretty close and DTS takes up more space. If your asking so you can do your movies I usually leave the 5.1 off and keep AC3 tracks that are now called Dolby Digital suround and can be 2 channel all the way up to 7.1. It takes up less space and most folks won’t notice a difference in the sound.

so if a movie has DTS and AC3 Audio you only need to have one or the other, not both??

DTS is uncompressed, thats the main difference anyway

Yes you only need one, however if there are directors commentaries and like that they’ll be smaller tracks probably in DD 2.0 so if you want those too remember to leave them in.