After the portage sync today, ffmpeg-1.0.8 complained about libsdl-1.2.15-r4. Indeed, libsdl had got a new USE flag 'sound'. Changing the ebuild of libsdl replacing the USE flag 'sound' by 'audio' fixed that. Note: I am using paludis (cave). Reproducible: Always
Flag "audio" was renamed to "sound", see bug 357661. Please re-sync and try again.