Hello,

I don't know if there is a tooltype to select the language, but in command line you can type:

mplayer -dvd 1 -dvd-device ide.device:unit -alang de

for german. en for english, fr for french, ja for japan...etc
Note that dvd-device argument is not needed if your DVD drive is connected on ide.device unit 1.

if you want subtitles you add the argument: -slang de (for german for example)

Also you can activate framedropping if needed by adding:
-framedrop

Regards