The 4th generation Supra, of which I am a proud owner of one, is usually called mkiv so all the fanboys keep talking about when the mkv is coming out, etc. But in "Jetee context" I think it might more likely be the
Matroska Multimedia Container Matroska though I recall you also appreciate the MkIV Supra.
I'm pretty sure I noticed one of the anime things I was watching a few days ago was in mkv format and my VLC media player handled it no problems as usual.