Merge and extract multimedia streams.
# To display information about a Matroska file:
mkvmerge --identify <path/to/file.mkv>
# To extract the audio from track 1 of a specific file:
mkvextract tracks <path/to/file.mkv> <1>:<path/to/output.webm>
# To extract the subtitle from track 3 of a specific file:
mkvextract tracks <path/to/file.mkv> <3>:<path/to/subs.srt>