Bad quality youtube videos

[zourich]

zourich last edited by

When i watch youtube videos in normal mode everything seems fine, but when switch to fullscreen it's getting too pixelated like this:
http://oi60.tinypic.com/rsy54g.jpg

and now same video in Firefox, the difference is obvious
http://oi61.tinypic.com/15s39c3.jpg

both are set to 1080p

what can be causing it?