MKV Files - AUD Units?

[michaelsft]

Hi all, does anyone know if there is an app to check if MKV 4k files have AUD units within the stream? Apparently for UHD players capable of playing BDXL discs they need them and often MKV have had them stripped out. I can't pretend to know exactly how this works but I guess if someone is creating the MKVs they might have an idea?