I was having trouble casting the chrome tab video @ 720p on my i7 laptop. I tried everything and it would only let me cast 480p smoothly. Today I checked the Google Cast extension and saw that it has a new update version on 9/25. My version was older (9/5 I think) but there is no update button for extension for Chrome. I normally use Firefox. So I had to delete it and install it again to get the new one. Once I got the new one, it cast 720p smoothly! I still get a tiny hiccup once about every 10 minutes but it was definitely watchable now.