media-sound/mp3splt-gtk requires SnackAmp http://snackamp.sourceforge.net/ to be installed - without it, it is almost unusable since player is used to select split points. However this player is not available in portage. New version - 0.5 - allows to use Audacious instead, but it requires passing --enable-audacious to configure. With this modification it works ok. Version 0.4 allowed to use Beep Media Player, but I am not sure if it was compatible with media-sound/bmpx Adding dependency on audacious and extra option for configure in ebuild 0.5 seems to me to be good choice.
mp3splt-gtk-0.5.2 is in portage with USE audacious. thanks for reporting.
