> Some container formats allow embedding the subtitles, but we would need to
> embed all subtitles in all language variants of all video files, and this
> seems like more work.

.mkv does and while ffmpeg needs to copy the whole stream to embed subtitles,
mkvtoolnix can do in place, which means it would take a fraction of a second to
insert/remove subtitles.

-- 
Pierre Neidhardt
https://ambrevar.xyz/