no. I don't see any need for that
Why? I already explained it o: I want to play some ambient sounds and they may overlap. Games need atmosphere. If I use wavs they are 2 MB big but if I use MP3s they are only 200 kB big. It would be insane if I only would use 15 of them (30 MB versus 3 MB and 15 wouldn't be much soundfiles). My internet connection will die and my beta testers will complain about the huge download.
Also MP3 is a very common format, more common than wav. Why is there no need for this and why does PLAYMUSIC support MP3s and PLAYSOUND does not?
and it's definitely not doable x-platform for me.
There are several ways to implement this:
You could decode the MP3 and save it as a wav on the harddisk and then you could play it. Or you could decode it and load it into the ram. Should work for any platform. Decoding MP3s shouldn't be that hard. I would even code it, if you want.