Go to Settings/Apps/TV and Video and turn OFF Fast Start. What this will do is "force" the ATV download the best quality video Available - not the best video it THINKS THINKS your connection can support. If you are on a fast connection like I am it will take an extra few minutes to buffer your stream but it will give you the highest quality available. Wow the 4K on Transformers and Power Rangers and John Wick looked glorious. If Fast Start is turned on, it claims to play the best quality available for your stream, but it really doesn't. My broadband is usually a fairly stable 120 MBPS (I use a hardwired connection most of the time) and it still delivers a lower quality stream. But, if Fast Start is turned off it will deliver the highest quality available - no matter what it detects your internet speed is. So you just may have to wait a few minutes before it starts.