ok thanks anyway
but i mean its just pressing the key "b" - why does it has to be supported by the interface?
Becasue that is how programs work. yes you are only pressing 'b' key but the client program (VLC remote in this case) is talking to and sending instructions to the server program (In this case VLC on your computer).
The Developers of Server programs expose certain commands to developers of client programs, this is called
API. In this case, what CV is saying is VLC has not (currently
1) provided the API for language/audio switch on DVD playing.
I hope this helps explain a little better what CV is saying.
1I say currently because CV (and probably other developers) is communicating with The VLC developers to make more exposure in the HTTP interface (the API used by the Remote Program)