ubuntu-restricted-extras has the gstreamer plugins (including that for mp3) and libxine1-ffmpeg is a plugin for xine and since amarok is using phonon witch is using xine ( phonon-backend-xine ) you need the xine mp3 plugin to be able to play mp3s
ubuntu- restricted- extras has the gstreamer plugins (including that for mp3)
and libxine1-ffmpeg is a plugin for xine and since amarok is using phonon witch is using xine ( phonon-backend-xine ) you need the xine mp3 plugin to be able to play mp3s