I don't know if mpegStreamclip will handle those, but they probably would open in DVD pro, which is part of your Final Cut suite. In that case your files will be something like hd_vob, as I recall it. PS looking at a previous thread from you, this isn't hdv anymore, it is sd for dvd.you might possibly have HD DVD, which Final cut (I notice you are using) can still make, or more accurately, DVD Pro, although that is a dead format. If you are in Final Cut, as I think you mentioned elsewhere, quicktime export should work.since it doesn't, either you are doing dealing with the files as mpegs - don't-or you need to select another setting in quicktime output. Probably the defaults will work fine, but if your system doesn't read the codec that msc selects, try another that you know is on your system. When you export, a window opens with a lot of codec and setting choices. I don't know what you want to do with the file, but if you want to edit it in an editing program, dv stream will work with almost anything. You can export in a variety of ways and convert also (file > export or file > convert). You can also simply select Open DVD and it will start with one of the files I don't use this but it works ok.
If they don't drag, file > open and navigate to the file.
Look at the video folder on the dvd and pull the vob files, one at a time (it doesn't batch) and drop them on the mpegStreamclip window. Forget about "the files are mpeg", you just work with the vob files as such. (As you may know, on a video dvd, the audio and video are separated and are separate files. In that case, you just need to remux (re-join the video and audio files) and export.mpegStreamclip should work fine, that is its primary function.