With BSplayer you can view only decrypted (not protected) DVDs..
So, the only VOB files you'll be able to see/screen-capture are the title ones (and not for all the available films..)
If you want to see protected DVDs, you have to use on-the-fly decrypters (such as DVD Region+CSS Free from
DVDIdle), otherway you have to copy the DVD to your hard disk (with unprotecting tools). but this method sould be illegal