[streaming] dvd audio track streaming

[exameron]

please, can you help me?
i'm not a mailing list component but you are my last hope!
i use vlc in linux (debian etch) and i want to extract specific streams 
from a dvd title: the stream video, the second stream audio and the 
third stream subtitle...all contained into the first dvd title.
the command i use is the sequent:
$ vlc dvd:/dev/dvd at 1 --audio-track 1 --sub-track 2 --sout file/ps:film.vob
...or, in extended version...
$ vlc -vvv dvd:/dev/dvd at 1 --audio-track 1 --sub-track 2 --sout 
"#standard{access=file,mux=ps,dst=film.vob}"
and now the question: in the output file, the video and the subtitle 
streams are the same that i require... but the audio no! it's first 
track audio of the title... not the second i require!
i've tried with others dvd, and the problem is the same: the output 
contains the video title and the sub stream i require... instead the 
audio is the first audio track again... is ever the first track, in 
spite of the value i set in the command.
what's the matter?
thank you very much and sorry for my bad english!
:-D