Media file wont play in full screen

Hello All, I cant get the Xbox one app to play my media files in full screen. My files are MKV container, MPEG-4 AVC Video , Display aspect ratio 16:9, but when it plays through the app, it crops the top and bottom, leaving blanks. I have tried to find a setting that will sort this out, but no luck. Plays fine through the plex media player on my pc, goes full screen. Tried casting it to my Xbox, this does’nt work either. Please help as its really annoying.

It sounds like an issue with your TV picture settings. Are you sure it’s not being zoomed in?