If you still have subtitles no matter what settings you use when ripping the DVD, you might have closed caption subtitles. They are common on NTSC DVDs. I don't use Mac the Ripper, and my solution to removing them from MPEG-2 streams is PC specific, but I thought I would pass on the general information, in case it helps. (I had never heard of them until I came across the problem myself.) CC subs shouldn't survive conversion to AVI, which I assume is part of your workflow; if you do see subs after conversion, they are likely burnt in, in which case you are stuck with them unless you can find an alternative source that does not have them.