Wrong "Codec ID:" for VTT in mkv file

[ibrshv]

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Description of your issue, suggested solution and other information

youtube-dl writes the unsupported "Codec ID: D_WEBVTT/SUBTITLES" in mkv so mkvextract can't extract subtitles. Correct is "S_TEXT/WEBVTT". Seems it's a problem with ffmpeg. If so maybe exists solutions to tackle this issue in a different way? Or simply, how can I get this data from mkv?

[dstftw]

Provide the output of exact downloading command that reproduces the problem.

[fcartegnie]

Provide the output of exact downloading command that reproduces the problem.

See example on :
https://trac.videolan.org/vlc/ticket/24949

The early unspecified D_ mappings have never been really in use and originates from WEBM.
https://www.webmproject.org/docs/container/

The correct payload for MKV mapping is through S_TEXT/WEBVTT,
but ffmpeg still uses the WEBM one, and only when codecs are WEBM compatible.

https://github.com/FFmpeg/FFmpeg/blob/c3cd6b765ba65469401ece256d79b2ac15ac4a9f/libavformat/matroskaenc.c#L2842

To me that's an ffmpeg issue

[srussel]

The ffmpeg issue
https://trac.ffmpeg.org/ticket/5641