DVB Subtitle support in mkv files ( S_DVBSUB )

DVB Subtitles are a common way of attaching subtitles in TV(DVB)-streams. VLC has long been able to play the subtitles properly with .ts -files along with the videostream. For long time preservation and future compatibility it is essential (at least for me) to be able to transcode the recordings to another format.

I have TVHeadend as PVR backend, and it can create both .ts files and .mkv -files. The .ts-files play fine with VLC but .mkv -files give an error that states that a codec could not be identified (referring to the S_DVBSUB stream).

Also, if I transcode the .ts -file with either MKVToolNix of FFMpeg to a .mkv file by simply copying all of the streams, VLC can not play the subtitles.

There are other software that can play the subtitles correctly (to mention some: Kodi, FFPlay, MPC-HC, SMPlayer, Plex). But I really do like VLC as a general purpose player, and I'd wish to see the DVB Subtitle support in .mkv-files to be added.

I've understood that S_DVBSUB has not been officially included in mkv specifications, but I did some searching and found this: https://github.com/Matroska-Org/matroska-specification/pull/77 , apparently the the S_DVBSUB codec specs have been included in mkv database since Jan 2017. Though I have no know if this is a relevant fact.

I'm more than happy to provide some short sample videos if needed, I'll do some short sample recordings.