Mplayer silently drops ass support if compiled against the stable libass-0.9.9. Honestly, I haven't checked whether libass-0.9.10 (also unstable) would suffice. With 0.9.11 mplayer works as expected Reproducible: Always
The trunk's 'configure' script checks for: #if !defined(LIBASS_VERSION) || LIBASS_VERSION < 0x00910000 which matches libass-0.9.10/libass/ass.h: #define LIBASS_VERSION 0x00910000 but not libass-0.9.9/libass/ass.h: #define LIBASS_VERSION 0x00909000 Thus, I think the ebuild should now require >=0.9.10.
Fixed in main tree. Thanks for report.