...”Yonhap source says the Nork launch was from a submarine, that would be huuge”....
Not really this possibility was already ‘seen’ and photographed potentially being set up with one of their subs at a port .....
this says launch site was from vicinity of Pyongsong
http://english.yonhapnews.co.kr/news/2017/11/29/0200000000AEN20171129000652315.html