I'm trying to decide between the Mi box S and the new Firestick 4K, mainly for IPTV and movie apps like terrerium tv. The Firestick has auto refresh rate. I've heard it works well on the fire TV 3. I keep hearing about the mi box 3 and no auto refresh rate even on Oreo 8.0. From what I've read it doesn't even work properly on the shield unless the the developer of the app you need it for implements the code to work with it. Will it be added properly on 8.1 of android TV does anyone know?
Apps have to be coded to support Frame Rate Matching - Application Programming Interfaces in any OS you choose. You have to make sure each App you need actually works.
Here is what the 4K Roku media players can do:
https://support.roku.com/en-gb/article/115012823268-how-to-change-the-display-refresh-rate-to-match-the-native-format-of-each-movie-video-or-tv-show
Here is what the new Fire TV Stick can supposedly do (untested):
http://www.aftvnews.com/amazon-fire-tv-stick-4k-will-support-video-frame-rate-matching/
This is what the Apple TV 4/4K can do with various Apps like Netflix, Plex, Emby, MrMC, Infuse, Amazon Prime & more:
https://support.apple.com/en-au/HT208288
The Shield has Auto Frame rate matching for Apps like Kodi, MrMC, SPMC, Plex, Emby.
But not for Apps like Netflix & Amazon Prime. The Apps developers are simply not interested. And it is up to the Apps developers to implement such a feature.
The Mi Box has No support whatsoever for Frame Rate Matching with any App. The new S model will not have it either no matter what the OS version is. Xiaomi really do not care about such a feature it seems.