SOLVED: Trouble with EIA 608 captions in .ts file

[TheDreadPirate]

Figured out how to deal with these kinds of files. Though the file you sent me was corrupt around the 16:10 mark so the conversion failed to fully complete. But it output enough to test the concept.

Code:

ffmpeg -y -i video.ts -f lavfi -i "movie='video.ts'[out+subcc]" -map 0:v -map 0:a -map 1:s:0 -c:v copy -c:a copy -c:s srt -max_muxing_queue_size 2048 -max_interleave_delta 0 -avoid_negative_ts disabled newFile.mkv

When I play the resulting file in MPV still shows the EIA 608 subs in addition to the converted SRT subs (required for MP4/MKV), but the SRT subs are present in Jellyfin.

You could implement this in a post processing script if all your content has EIA 608 subs.