Extract subtitles from MKV in C#

dotnet new console -o MkvSubs && cd MkvSubs
dotnet add package RecursiveAI.OneMedia --version 0.4.0-preview.1
curl -L -o test5.mkv https://raw.githubusercontent.com/ietf-wg-cellar/matroska-test-files/master/test_files/test5.mkv

using RecursiveAI.OneMedia;
using RecursiveAI.OneMedia.Captions;
 
using MediaFile media = Media.Open("test5.mkv");
 
// Every subtitle source in the file: text and bitmap tracks, then teletext pages and
// CEA-608/708 captions found in the video (finding those reads the video once).
foreach (SubtitleTrack sub in media.Subtitles)
{
    string path = $"test5.track{sub.Track.Index}.{sub.Language ?? "und"}.srt";
    ConversionReport report = Subtitles.Write(sub.Document, path);
    Console.WriteLine($"{sub.Kind} {sub.Codec} track {sub.Track.Index} ({sub.Language}): {sub.Cues.Count} cues -> {path}");
    foreach (ConversionLoss loss in report.Losses)
        Console.WriteLine($"  {loss.Kind} {loss.Feature}: {loss.Message}");
}

Text S_TEXT/UTF8 track 2 (eng): 5 cues -> test5.track2.eng.srt
  Dropped Language: The document language is not carried.
Text S_TEXT/UTF8 track 3 (hun): 6 cues -> test5.track3.hun.srt
  Dropped Language: The document language is not carried.
Text S_TEXT/UTF8 track 4 (ger): 6 cues -> test5.track4.ger.srt
  Dropped Language: The document language is not carried.
Text S_TEXT/UTF8 track 5 (fre): 6 cues -> test5.track5.fre.srt
  Dropped Language: The document language is not carried.
Text S_TEXT/UTF8 track 6 (spa): 6 cues -> test5.track6.spa.srt
  Dropped Language: The document language is not carried.
Text S_TEXT/UTF8 track 7 (ita): 6 cues -> test5.track7.ita.srt
  Dropped Language: The document language is not carried.
Text S_TEXT/UTF8 track 9 (jpn): 6 cues -> test5.track9.jpn.srt
  Dropped Language: The document language is not carried.
Text S_TEXT/UTF8 track 10 (und): 6 cues -> test5.track10.und.srt

head -11 test5.track2.eng.srt

1
00:00:03,549 --> 00:00:05,290
...the colossus of Rhodes!
 
2
00:00:05,757 --> 00:00:06,678
No!
 
3
00:00:06,715 --> 00:00:12,544
The colossus of Rhodes

i=0
for t in 2 3 4 5 6 7 9 10; do
  ours=$(ls test5.track$t.*.srt)
  ffmpeg -v error -y -i test5.mkv -map 0:s:$i ffmpeg.s$i.srt
  echo "$ours: ours $(grep -c -- '-->' $ours) cues, ffmpeg $(grep -c -- '-->' ffmpeg.s$i.srt) cues, $(cmp -s $ours ffmpeg.s$i.srt && echo identical || echo different)"
  i=$((i+1))
done

test5.track2.eng.srt: ours 5 cues, ffmpeg 5 cues, identical
test5.track3.hun.srt: ours 6 cues, ffmpeg 6 cues, identical
test5.track4.ger.srt: ours 6 cues, ffmpeg 6 cues, identical
test5.track5.fre.srt: ours 6 cues, ffmpeg 6 cues, identical
test5.track6.spa.srt: ours 6 cues, ffmpeg 6 cues, identical
test5.track7.ita.srt: ours 6 cues, ffmpeg 6 cues, identical
test5.track9.jpn.srt: ours 6 cues, ffmpeg 6 cues, identical
test5.track10.und.srt: ours 6 cues, ffmpeg 6 cues, identical