[FFmpeg-trac] #11105(undetermined:new): webvtt codec not seeking properly with output seeking

[FFmpeg]

#11105: webvtt codec not seeking properly with output seeking
-------------------------------------+-------------------------------------
             Reporter:  Tristan      |                    Owner:  (none)
  Matthews                           |
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:
                                     |  undetermined
              Version:  git-master   |               Resolution:
             Keywords:  webvtt       |               Blocked By:
  caption seeking                    |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
Comment (by Tristan Matthews):

 The subtitles don't display at the expected times unless I use `-c:s
 copy`. The subtitle track is present according to ffprobe however:

 {{{
 # when using `-c:s webvtt

 Input #0, matroska,webm, from 'trimmed.mkv':
   Metadata:
     COMPATIBLE_BRANDS: isomiso6iso2avc1mp41
     MAJOR_BRAND     : isom
     MINOR_VERSION   : 512
     ENCODER         : Lavf61.5.101
   Duration: 00:00:13.75, start: -0.005000, bitrate: 2212 kb/s
   Stream #0:0(eng): Video: h264 (Constrained Baseline), yuv420p(tv, bt709,
 progressive), 1920x1080, SAR 1:1 DAR 16:9, 59.71 fps, 59.71 tbr, 1k tbn
 (default)
       Metadata:
         HANDLER_NAME    : VideoHandler
         VENDOR_ID       : [0][0][0][0]
         DURATION        : 00:00:13.748000000
   Stream #0:1(eng): Audio: ac3, 48000 Hz, stereo, fltp, 192 kb/s (default)
       Metadata:
         HANDLER_NAME    : SoundHandler
         VENDOR_ID       : [0][0][0][0]
         ENCODER         : Lavc61.10.100 ac3
         DURATION        : 00:00:13.728000000
   Stream #0:2: Subtitle: webvtt
       Metadata:
         ENCODER         : Lavc61.10.100 webvtt
         DURATION        : 00:00:00.000000000
 }}}

 {{{
 # when using -c:s copy

 Input #0, matroska,webm, from 'trimmed.mkv':
   Metadata:
     COMPATIBLE_BRANDS: isomiso6iso2avc1mp41
     MAJOR_BRAND     : isom
     MINOR_VERSION   : 512
     ENCODER         : Lavf61.5.101
   Duration: 00:00:13.76, start: -0.005000, bitrate: 2210 kb/s
   Stream #0:0(eng): Video: h264 (Constrained Baseline), yuv420p(tv, bt709,
 progressive), 1920x1080, SAR 1:1 DAR 16:9, 59.71 fps, 59.71 tbr, 1k tbn
 (default)
       Metadata:
         HANDLER_NAME    : VideoHandler
         VENDOR_ID       : [0][0][0][0]
         DURATION        : 00:00:13.748000000
   Stream #0:1(eng): Audio: ac3, 48000 Hz, stereo, fltp, 192 kb/s (default)
       Metadata:
         HANDLER_NAME    : SoundHandler
         VENDOR_ID       : [0][0][0][0]
         ENCODER         : Lavc61.10.100 ac3
         DURATION        : 00:00:13.760000000
   Stream #0:2: Subtitle: webvtt
       Metadata:
         DURATION        : 00:00:13.720000000
 }}}

 The issue is that I wouldn't expect the `webvtt` codec to effectively
 nullify the subtitles in this instance.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/11105#comment:2>
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