How to split a large mkv file into parts with the *.srt subtitle file separated accordingly?

Question

At UNIX command line, I use the mkvmerge command in MkvToolNix to split the large multi-GB *.mkv file into several parts:

mkvmerge -o out.mkv --split 1990M large.mkv

It generated out-001.mkv, out-002.mkv, out-003.mkv.

There is also a subtitle file large.srt. Now I do I separate it into parts that will work properly with those smaller mkv files?

Another related question: how to incorporate large.srt into large.mkv first, and then split the resultant mkv file into smaller parts retaining the subtitles?

Answer 1

Add the subtitles to your large mkv file first. Then mkvmerge will split the file with the subtitles automatically.

To add the subtitles, the easiest is to use mkvmerge-GUI. It will also show you the command-line it uses. Or you can try something like this directly:

video="your_large_video.mkv"
st_en="english.srt"
st_fr="french.srt"
out="large_video-st_en_fr.mkv"

mkvmerge -o "$out" "$video" --language 0:eng "$st_en" --language 0:fre "$st_fr"

After that, splitting works fine and includes correct subtitles. I just tried it, and splitted by size and by duration. I'm not sure, but maybe the subtitle timing was preserved more exactly when splitting by duration (--split 1800s or similar instead of --split 500M).