Thanks for the info. What about the possible new product coming out at the end of this month?
[doublepost=1460634070][/doublepost]Is there anything that I can do to those 4K videos so that slower computers can play them back? Perhaps some how convert them to non-4K videos via my iPhone?
It seems that the 13" and 15" Macbook strongly rumoured to be announced at WWDC in June will be capable of 4K playback, although more information was behind a Taiwanese newspaper paywall.
As the other people have mentioned, slower computers can convert 4K via handbrake on those macs or the mac you get.
For reference, my iMac 2011 27" can playback 4K on the 1440p screen and the FHD TV screen with minimal lag, it is not significant until it has less than 3GB free ram.
I would suggest that if you purchase a Macbook with the core M processor, it will not be fast enough to display 4K smoothly, as the performance is roughly as slow as a 2013 Mac Mini.
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There is always the iPad Pro
While the iPad Pro 9.7" has the best screen, it does not have 4K on that screen, so there would be a need for the adapter as the current AppleTV doesn't have 4K.
It maybe possible to get the right results for 4K if you have a Sony Android UHD TV and the Airparrot app, however I have yet to test this app with my Sony Android FHD TV.
The main benefit of the Android TV is when you run Plex on your networked Macs and SANs to the Plex app for your home library of Movies, TV and Music.