What is DVDSUB?

[comparison8192]

I couldn't find any answers on this on Google, and Jellyfin codec documentation only talks about DVB-SUB and VobSub. These subtitles were created/exported by MakeMKV. What are these subtitles supposed to be? Are they text or image-based?

[TheDreadPirate]

They are both the same thing, essentially. And they are image based subs.