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

[FFmpeg]

#9839: Dash mpd subtitle incorrect container
-------------------------------------+-------------------------------------
             Reporter:  Solaris      |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:  git-
  undetermined                       |  master
             Keywords:  dash         |               Blocked By:
  dashencoder DASH webvtt            |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:
 I am trying to convert mkv file with multiple audio/sub streams to mpeg-
 dash. As per the example in the wiki , I am able to create adaptation sets
 for video and audio but unable to include subtitles.
 Expected: ffmpeg will convert srt subs to webvtt and include it in mpd as
 text/vtt
 But ffmpeg is trying to use mp4 container for webvtt and thus throw a
 error

 {{{
 [dash @ 000001ea163eb3c0] No bit rate set for stream 4
 [dash @ 000001ea163eb3c0] Opening 'outNull/init-stream4.m4s' for writing
 [mp4 @ 000001ea1f32eb00] Could not find tag for codec webvtt in stream #0,
 codec not currently supported in container
 Could not write header for output file #0 (incorrect codec parameters ?):
 Invalid argument
 Error initializing output stream 0:3 --
 }}}

 How to reproduce:
 {{{
 % ffmpeg -y -i input.mkv -map 0:0 -map 0:1 -map 0:2 -map 0:0 -map 0:3
 -c:v:0 libx264 -c:a:0 aac -c:a:1 libopus -c:v:1 libvpx-vp9 -c:s:0 webvtt
 -b:v:0 800k -s:v:0 1280x720 -use_timeline 1 -use_template 1 -window_size 5
 -adaptation_sets "id=0,streams=0,3 id=1,streams=1 id=2,streams=2
 id=3,streams=4" -f dash outNull/out.mpd
 ffmpeg version : ffmpeg version 2022-07-18-git-cb22d5ea3c-full_build-
 www.gyan.dev
 }}}
 Patches should be submitted to the ffmpeg-devel mailing list and not this
 bug tracker.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/9839>
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