user10738: 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?

user3138: 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).

10738: <p>At UNIX command line, I use the <code>mkvmerge</code> command in <a href="https://www.bunkus.org/videotools/mkvtoolnix/" rel="nofollow">MkvToolNix</a> to split the large multi-GB *.mkv file into several parts:</p>

<pre><code>mkvmerge -o out.mkv --split 1990M large.mkv
</code></pre>

<p>It generated <code>out-001.mkv</code>, <code>out-002.mkv</code>, <code>out-003.mkv</code>.</p>

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

<p>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?</p>
 3138: <p>Add the subtitles to your large mkv file first. Then mkvmerge will split the file with the subtitles automatically.</p>

<p>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:</p>

<pre><code>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"
</code></pre>

<p>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 (<code>--split 1800s</code> or similar instead of <code>--split 500M</code>).</p>
