I've been trying to set extended properties of mp4 such as Director and Publisher, but those are nowhere to be found when I browse the File.Tag suggestions that visual studio gives me. Perhaps I'm just using a bad library or something, or could someone confirm that TagLib doesn't support these?
I do however get suggestions for File.Tag properties relevant to audio files such as Album and Performers. Perhaps it's only showing audio properties for mp4? Can you switch to video/movies somehow?
I'm using the windows edition from here: http://download.banshee.fm/taglib-sharp/2.1.0.0/. just dropped the dll in my project dir and laoded it in VC#.