I started by connecting my ATV 4k directly to my LG OLED and using ARC to feed AC3 to my AVR. The DV content I've watched (Netflix & iTunes) looks great and the surround sound is pretty good too -- not great, but it may be the streaming source, not sure. This setup should be fine until Apple adds Atmos, then I'll probably choose to watch 4k HDR w/ Atmos, over 4k DV w/ 5.1 (my AVR won't pass DV and my TV won't do DD+ via ARC).
I tried setting the output to both 30hz 4k DV and 24hz 4k DV and man the UI is not smooth, at all, when at 24hz and is noticeably jumpy at times on 30hz. Of course that isn't a big deal, as I got my TV to watch content, not menus. But I do see why Apple defaults it to 60hz -- it's still crazy that out-of-the-box it selected 4k HDR 60hz, instead of 4k DV 60hz.
As expected, the 3:2 pulldown doesn't work that great on my LG TV when watching 24p content at 30hz, so I'm very pleased Apple provided the ability to hard code to 24hz, which is what I'm going to leave it at until I notice a problem playing 30p content.
How good could it be if it isn't HD?
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