I have uninstalled dbpoweramp, because I am seeing that Directory Opus may be configured to display tooltip info from tags for audio files. I have configured the music file group with the following settings:
Why am I able to see tag info within the metadata panel but not from the tool tip? It seems to be an M4A file specific issue. When I view this same file's properties from Windows' property view, I do see tag content:
Please check the M4A example file I uploaded. Windows supports its tags, but Directory Opus does not. Even the metadata view only shows some of the tag info and not all.
Incidentally, Mediainfo is 100% open source, so you are able to download the complete source code to see how the developer interprets the Apple tag information. Apple's tag format is binary atoms.