portaudio v19 is getting unmasked, and we don't have pablio for it.. and it seems epos is actually shipping a own portaudio copy, either you should start using it (not very good idea), drop portaudio support entirely (maybe) or patch it to work with >=media-libs/portaudio-19_pre2007...
-r1 drops the USE portaudio, and the patch. needs to be ported into portaudio v19, might want to contact upstream.