Apparently, Kodi doesn't support acceleration from GPU for now, so when you read or stream a video, the CPU does all the job without help from GPU. tllim said that in this mode, all 1080p video can be read but 4k, in the new format H.265, is too hard for the CPU alone.
The others video player apps can read videos with CPU AND GPU, so even 4k can be read.
Kodi can improved this if they want to support Allwinner A64 hardware, but we don't known if the want to, and as another solution if they don't, i found Archos Video Player, a media center app that can be used as Kodi, to manage media library in local or network and use native player to read or stream 4k videos.
The others video player apps can read videos with CPU AND GPU, so even 4k can be read.
Kodi can improved this if they want to support Allwinner A64 hardware, but we don't known if the want to, and as another solution if they don't, i found Archos Video Player, a media center app that can be used as Kodi, to manage media library in local or network and use native player to read or stream 4k videos.