[FFmpeg-trac] #9839(undetermined:open): Dash mpd subtitle incorrect container

[FFmpeg]

#9839: Dash mpd subtitle incorrect container
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             Reporter:  Solaris      |                    Owner:  (none)
                 Type:  defect       |                   Status:  open
             Priority:  normal       |                Component:
                                     |  undetermined
              Version:  git-master   |               Resolution:
             Keywords:  dash         |               Blocked By:
  dashencoder DASH webvtt            |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Comment (by Solaris):

 What is the correct way to include subtitles/captions for dash ?

 Tried forcing container to webm with following:
 {{{
 ffmpeg -re -y -i input.mkv -map 0:0 -map 0:1 -map 0:2 -map 0:3 \
 -c:v:0 libvpx-vp9 -c:a:0 libopus -c:a:1 libopus -c:s:0 webvtt  \
 -b:v:0 800k -s:v:0 1280x720 \
 -use_timeline 1 -use_template 1 \
 -dash_segment_type webm -window_size 5 -adaptation_sets "id=0,streams=0
 id=1,streams=1 id=2,streams=2 id=3,streams=3" \
 -f dash outNull/out.mpd
 }}}

 Result: AdaptationSet 3 which should be type text is included as type
 audio with no codec and thus no caption in player
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Ticket URL: <https://trac.ffmpeg.org/ticket/9839#comment:2>
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