It's not uncommon to have a media file with several subtitle/audio languages
which user can select from. These can be DVD, MKV, OGM, but even external
subtitle/audio tracks for AVI (and other containers).

User should have an option to select which audio and subtitle languages he
prefers -- possibly to make some pairs and have certain priority.

For example, for me, this priority would be (audio/subs):
Japanese/English
Japanese/Czech
English/NO_SUBS
Czech/NO_SUBS
*/English
*/Czech

Implementing for DVD and MVK should be easy -- for example MKV uses ISO codes to
identify languages. There could be some hard time regarding OGM.

With external subtitles (for which support in Totem really sucks, because it
can't automatically load subs with filenames like "movie_name.lang.srt") and
audio tracks (which Totem doesn't support at all, AFAIK):
It's kind of de-facto standard that the last word betwen the last pair of
fullstops identifies language, like this:
movie_name.some.other.words.English.srt

For example, VSFilter.dll (favorite DirectShow subtitler filter) would match
this subtitle file for movie named "movie_name.mkv", so it can even leave the
"some.other.words" part out.