Avisynth is a scripting language and a collection of filters for simple (and not so simple!) non-linear video editing tasks. It frameserves video to applications.
MplayerXP is branch of well known mplayer (http://mplayerhq.hu) which is based on new (thread based) core. Main goal of this project is to achieve smoothness of video playback due monotonous CPU loading.
VIDIX is VIDeo Interface for linux. VIDIX is portable interface which was designed and introduced as interface to userspace drivers to provide DGA everywhere where it's possible.