the contrib/subrib directory is (and should be) empty, but you need files like subtitle2pgm,... to have full functionallity in dvdrip. The directory can be downloaded from http://subtitleripper.sourceforge.net/ The possible solution is to add it directly to the ebuild (don't know if it will be build when it is copied to contrib/subrib) or make a new ebuild and add a PDEPEND to transcode.
*** This bug has been marked as a duplicate of 90101 ***