Choppy and pixelated video on Macbook Air 5,1. Unable to run/view HD videos at all

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http://askubuntu.com – I'm currently running 13.04 (I try to extend the little help I can by submitting bug reports) and the video is extremely choppy and pix-elated on any video program I run (vlc, mplayer, totem etc.), any flash or html5 videos, and HD videos won't play in a reasonable way at all (entire frames get skipped and video footage is completely distorted; I would say it's about 10 FPS on HD videos, really extremely bad quality). Also, I had this exact problem on 12.04 and 12.10 and was kind of hoping 13.04 would be better, but it is not. Video in Mac OSX works excellent, no lag or quality loss, works per (HowTos)