[mamachan]

Have you enabled them in the whitelist?

 Yes.
I try to play a 1920x1080 24Hz .mkv video.
I add this resolution in whitelist, but Kodi play the file at 1920x1080 50Hz (i set this resolution by default on my shield).

Probably the file is at 23,997 Hz (and not 24Hz), i must match 1920x1080 23,997 in Kodi whitelist? I thinks i don't see this resolution in the list.

No problem with SPMC. The same file start regulary at 1920x1080 24Hz.  

I add 23,98 in the whitelist and now is all OK.

But now i have the same problem with 1280x720 50hz files.

If i set the Shield at 3840x2160 59,94 or 50/60 Hz i can't add any 1280x720 resolutions in Kodi whitelist
If i set the Shield at 1920x1080 59,94 or 50/60 Hz i can add 1280x720 resolutions in Kodi whitelist but the file are played always at 1920x180
Is correct?