PI 2 Cant play 4k video…
It’s not in the spec. Pi will officially play up to L4.1 H264 (although really 5.1 is doable) at 1080p
I don’t know how PI b+ guys able to play. I believe at least Pi2 should able to play but output will be 1080P.
I think 4K has to be in H265. Pi must decode H265 in software and this is extremely limited in terms of frame rate. You’d probably see about 15fps for 720p