S912 boxes – 4k content not playing full screen

Hi all,

I have the following S912 boxes : –
Beelink GT1 TV Box Octa Core Amlogic S912
ACEMAX M12N Smart TV Box Amlogic S912 Octa Core

I have the latest version of Kodi running on both boxes.

I am playing a 4k test file (Sintel) from the same source and it plays absolutely fine and at full screen on the ACEMAX M12N box.

full screen view :- http://oi63.tinypic.com/14kbeah.jpg
video information :- http://oi64.tinypic.com/25r1snm.jpg

The same file on the played from the same source on the Beelink GT1 however is in black bordered window and not full screen

Borders around the video :- http://oi64.tinypic.com/2cqz438.jpg
video information :- http://oi66.tinypic.com/20t455e.jpg

View mode is “Normal”in both instances.
Both boxes are set at 4k @ 60hz within the android display settings
Both boxes have the MediaCodec (Surface) and MediaCodec options selected in the Acceleration settings.

Anyone else experienced this behaviour? Could this be due to maybe one of the boxes being rooted and the other box not?

The only thing I have noticed with the Beelink box is that even if I set the GUI Resolution Limit to “Unlimited” within the spmc settings, the system information always shows 1920×1080 @ 60hz (even though the box is set to 4k @ 60hz in the android settings).

Please note that the boreded video behaviour can be seen on multiple other 4k files I have tried on the beelink box. The same files play fullscreen / without borders on the ACEMAX box.

Any help would be much appreciated

Many thanks in advance