Yes, I'm using the os4 mpega.library.
The mpega.library haven't been updated for years now, and there is no AmigaOS4 native version of it I think. For AmigaOS4 there is mpega_libmad.library, which is with the same functionality and even claims that it decodes better. So you actually used the mpega_libmad.library under AmigaOS 4.
