Jpcsp already uses FFMpeg (xuggle) for a lot of the audio (all platforms), there is just no open source or free codec for the Atrac 3 + (plus) format, and most psp games use that audio type for voice, movies, and sometimes BGM so in that respect ffmpeg is not going to help even though it has a very good codec selection, it's still missing that .
Try Out JPCSP Launcher v1.8.0.4 | How to post a log