[noggin]

This Apple TV 4K Firecore thread might be of interest to ALL - 3D ISO and MVC users....

Solution for Framepacked 3D for some folks and it works great! (click)

 I've often wondered if you could just create a 3840x2160/24p 2D signal with alternate lines sourced from alternate 3840x1080p (scaled from 1920x1080p) Left and Right eye feeds.  For a Passive 3D UHD TV this should 'just work'.  The problem is that encoding a 3840x2160p signal where you have to ensure no leakage between alternate lines is pushing an H264/H265 encoder quite hard, and you'll need high bitrates to avoid artefacts that split across eye feeds?

Effectively you are interleaving lines from each eye feed alternately?

if you can create a Full resolution SBS or TAB source that is then converted on playback to the interleaved format by a GPU process that would be a LOT better than encoding the interleaved format.