Has anyone had any luck with 4k60 content on the mibox YouTube app? The mibox itself shows it can connect at 4k60 in the display settings, but 4k60 content through YouTube seems to just revert to 1080p60 . 4k30 content seems to display fine, just no 4k60fps. My shield TV displays 4k60 in YouTube just fine.
Someone deceptively in my opinion, Xiaomi sells the device as being 4K 60fps capable, because the UI runs fine at those settings. As far as video goes, you'll notice in any promotional materials that they are careful to say that in terms of actual video only 4K at 30fps is supported for any codec.
I haven't tried 4K @ 60fps in recent firmware, but I tried an h.265 and an h.264 sample a long time ago and both ran like crap, appearing to speed up and slow down while also dropping a very noticeable amount of frames.
4K h.264 @ 30fps and 4K VP9 @ 30fps (youtube) seems to run fine these days without dropping any frames. Haven't tried h.265 4K 30fps in a while but I bet it works well too.