Video [q] aosp video lagging issue

well, I've been using touchwiz ROMS ever since I got this phone last year. I've tried a few AOSP roms and liked 'em.... but the one thing that made me shift back to TW ROMS is because the videos LAG in AOSP roms. I mean seriously? why would it lag? not all the videos but some of high resulation ones..... Does anyone know about this thing?