[FFmpeg-trac] #10510(undetermined:new): FFMPEG decode 608 caption to webvtt with big cues. How to generate with smaller cues (i.e. gop size)?

[FFmpeg]

#10510: FFMPEG decode 608 caption to webvtt with big cues. How to generate with
smaller cues (i.e. gop size)?
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             Reporter:  Qi Cao       |                     Type:
                                     |  enhancement
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:  caption      |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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 Summary of the bug: We are using FFMPEG to decode 608 caption to webvtt.
 webvtt files contains cues with large timespan, such as playing music for
 two minutes. Since we are getting this till the end of caption, it is too
 late to display the caption. We are wondering if we could decode the
 captions to smaller cues, such as gop size. We have been playing the
 segment command switch with no luck. Could you shad light on this?

 How to reproduce:
 ffmpeg -data_field first -y -t 10 -f lavfi -i
 "movie='fallbeatcaptiontest.mp4':streams='v+a'[out0+subcc][out1]" -c:v
 rawvideo -f rawvideo -pix_fmt nv12 -c:a pcm_s16le -f s16le -ar 16000 -ac 1
 -map a -map v -f nut base.nut -map 0:s -c:s webvtt -f webvtt cap-base.vtt
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Ticket URL: <https://trac.ffmpeg.org/ticket/10510>
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