Just FYI, Someone from Amiga forums is working to improve video playback codec and mplayer for Altivec in general, and plans to contribute code to upstream library maintainers so it is not Amiga-specific.
http://www.amigans.net/modules/xforum/viewtopic.php?topic_id=6723&forum=25
yup, that's me :)
https://github.com/markos/FFmpeg
I'm getting 5-10% on average (though I got more in some clips), and I think I can get more than that. I'll contribute the patches back to both ffmpeg/libav when I'm done.
Well done Markos! It sounds very good! :)