[Mosu]

Automatic conversion from fra to fre is what mkvmerge already does. The thing about standards is that you cannot change them willy nilly. This applies to the Matroska specs, too. Like I said we started out with the bibliographic forms of 639-2, and simply changing over to the terminology ones would either invalidate existing files or make players that only support the bibliographic ones seem suddenly buggy – although they've been perfectly compliant with the specs in the past.

If we ever do something about the codes then we will likely introduce a new element that'll use 639-3 to be used alongside with the older 639-2/B elements. For improved backwards compatibility both elements would have to be used at the same time.