Is this when you are compressing or ripping a 1:1 copy? Are you
getting two separate files or showing two "titles" in the file?
If you are trying to compress, you need to identify and select the
correct title to compress. If you are showing two "titles" and either
could be the movie, one may be wide screen and the other full screen.
Also, if the protection isn't completely removed, you may have
multiple titles of sufficient time length that any could be the
movie. In this case, you have to determine which title is the actual
movie.
To determine which is the correct title, you have to play the ripped
1:1 DVD file or the actual DVD. If you are using Mac's DVD Player,
make sure you have selected play in the DVD menu for the movie start
and have given it enough for the movie to begin playing. In the above
drop down menu, select "Go", then "Title", scroll down to see which
title number is checked. Remember that's "Title", not "Chapter".