[FFmpeg-trac] #7117(avcodec:open): DVB subtitles render incorrectly

[FFmpeg]

#7117: DVB subtitles render incorrectly
------------------------------------+-----------------------------------
             Reporter:  leoenc      |                    Owner:
                 Type:  defect      |                   Status:  open
             Priority:  normal      |                Component:  avcodec
              Version:  git-master  |               Resolution:
             Keywords:  dvbsub      |               Blocked By:
             Blocking:              |  Reproduced by developer:  1
Analyzed by developer:  1           |
------------------------------------+-----------------------------------
Changes (by cehoyos):

 * status:  new => open
 * reproduced:  0 => 1
 * component:  undetermined => avcodec
 * keywords:   => dvbsub
 * version:  unspecified => git-master
 * analyzed:  0 => 1


Comment:

 Afaict, the issue is that the dvbsub encoder does not write a ''Display
 definition segment'', see also 1fc20af6af3ec31d0ee665557885b6c20c6d3686
 Reproducible with the following command, I will delete most attachments:
 {{{
 $ ffmpeg -f lavfi -i color=s=hd1080 -fix_sub_duration -i subtitles.sup
 -scodec dvbsub -qscale 2 -mbd 2 -t 30 out.ts
 ffmpeg version N-90583-g5710fda Copyright (c) 2000-2018 the FFmpeg
 developers
   built with gcc 6.3.0 (GCC)
   configuration: --enable-gpl
   libavutil      56. 12.100 / 56. 12.100
   libavcodec     58. 17.100 / 58. 17.100
   libavformat    58. 10.100 / 58. 10.100
   libavdevice    58.  2.100 / 58.  2.100
   libavfilter     7. 14.100 /  7. 14.100
   libswscale      5.  0.102 /  5.  0.102
   libswresample   3.  0.101 /  3.  0.101
   libpostproc    55.  0.100 / 55.  0.100
 Input #0, lavfi, from 'color=s=hd1080':
   Duration: N/A, start: 0.000000, bitrate: N/A
     Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 1920x1080
 [SAR 1:1 DAR 16:9], 25 tbr, 25 tbn, 25 tbc
 Input #1, sup, from 'subtitles.sup':
   Duration: N/A, start: 3.440000, bitrate: N/A
     Stream #1:0: Subtitle: hdmv_pgs_subtitle, 1920x1080
 Please use -q:a or -q:v, -qscale is ambiguous
 Stream mapping:
   Stream #0:0 -> #0:0 (rawvideo (native) -> mpeg2video (native))
   Stream #1:0 -> #0:1 (hdmv_pgs_subtitle (pgssub) -> dvb_subtitle
 (dvbsub))
 Press [q] to stop, [?] for help
 [sup @ 0x21bf140] Invalid timestamps stream=0, pts=0, dts=303570,
 size=4974
 Output #0, mpegts, to 'out.ts':
   Metadata:
     encoder         : Lavf58.10.100
     Stream #0:0: Video: mpeg2video (Main), yuv420p, 1920x1080 [SAR 1:1 DAR
 16:9], q=2-31, 200 kb/s, 25 fps, 90k tbn, 25 tbc
     Metadata:
       encoder         : Lavc58.17.100 mpeg2video
     Side data:
       cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: -1
     Stream #0:1: Subtitle: dvb_subtitle (dvbsub), 1920x1080
     Metadata:
       encoder         : Lavc58.17.100 dvbsub
 [sup @ 0x21bf140] Invalid timestamps stream=0, pts=0, dts=767997,
 size=6238
 [sup @ 0x21bf140] Invalid timestamps stream=0, pts=0, dts=1135096,
 size=9926
 [sup @ 0x21bf140] Invalid timestamps stream=0, pts=0, dts=1635183,
 size=17502
 [sup @ 0x21bf140] Invalid timestamps stream=0, pts=0, dts=2218393,
 size=18698
 frame=  750 fps=213 q=2.0 Lsize=    2809kB time=00:00:29.92 bitrate=
 769.0kbits/s speed= 8.5x
 video:2470kB audio:0kB subtitle:65kB other streams:0kB global headers:0kB
 muxing overhead: 10.795754%
 }}}

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Ticket URL: <https://trac.ffmpeg.org/ticket/7117#comment:3>
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