[FFmpeg-trac] #4781(undetermined:new): Automatic subtitle scaling

[FFmpeg]

#4781: Automatic subtitle scaling
-------------------------------------+-------------------------------------
               Reporter:  cehoyos    |                  Owner:
                   Type:  defect     |                 Status:  new
               Priority:  normal     |              Component:
                Version:  git-       |  undetermined
  master                             |               Keywords:  sub
             Blocked By:             |               Blocking:
Reproduced by developer:  0          |  Analyzed by developer:  0
-------------------------------------+-------------------------------------
 One sample attached to ticket #679 contains subtitles which are shown with
 correct size by FFplay but cannot be overlayed unless scaled manually.
 {{{
 $ ffmpeg -i oversized_pgs_subtitles.mkv -filter_complex [0:0][0:4]overlay
 -qscale 2 -t 5 out.avi
 ffmpeg version N-74483-gb807f7e Copyright (c) 2000-2015 the FFmpeg
 developers
   built with gcc 4.7 (SUSE Linux)
   configuration: --enable-gpl
   libavutil      54. 30.100 / 54. 30.100
   libavcodec     56. 57.100 / 56. 57.100
   libavformat    56. 40.101 / 56. 40.101
   libavdevice    56.  4.100 / 56.  4.100
   libavfilter     5. 34.100 /  5. 34.100
   libswscale      3.  1.101 /  3.  1.101
   libswresample   1.  2.101 /  1.  2.101
   libpostproc    53.  3.100 / 53.  3.100
 [matroska,webm @ 0x35e14e0] Could not find codec parameters for stream 3
 (Subtitle: hdmv_pgs_subtitle): unspecified size
 Consider increasing the value for the 'analyzeduration' and 'probesize'
 options
 Input #0, matroska,webm, from 'oversized_pgs_subtitles.mkv':
   Metadata:
     encoder         : libebml v1.3.0 + libmatroska v1.4.1
     creation_time   : 2014-05-18 14:26:43
   Duration: 00:00:09.57, start: 0.000000, bitrate: 642 kb/s
     Stream #0:0(eng): Video: h264 (High), yuv420p(tv, bt709), 848x480, SAR
 1:1 DAR 53:30, 23.98 fps, 23.98 tbr, 1k tbn, 180k tbc (default)
     Stream #0:1(eng): Audio: vorbis, 48000 Hz, mono, fltp (default)
     Stream #0:2(jpn): Audio: vorbis, 48000 Hz, mono, fltp
     Stream #0:3(eng): Subtitle: hdmv_pgs_subtitle (default)
     Stream #0:4(eng): Subtitle: hdmv_pgs_subtitle, 1920x1080
 Please use -q:a or -q:v, -qscale is ambiguous
 Output #0, avi, to 'out.avi':
   Metadata:
     ISFT            : Lavf56.40.101
     Stream #0:0: Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 848x480 [SAR
 1:1 DAR 53:30], q=2-31, 200 kb/s, 23.98 fps, 23.98 tbn, 23.98 tbc
 (default)
     Metadata:
       encoder         : Lavc56.57.100 mpeg4
     Stream #0:1(eng): Audio: ac3 ([0] [0][0] / 0x2000), 48000 Hz, mono,
 fltp, 96 kb/s (default)
     Metadata:
       encoder         : Lavc56.57.100 ac3
 Stream mapping:
   Stream #0:0 (h264) -> overlay:main (graph 0)
   Stream #0:4 (pgssub) -> overlay:overlay (graph 0)
   overlay (graph 0) -> Stream #0:0 (mpeg4)
   Stream #0:1 -> #0:1 (vorbis (native) -> ac3 (native))
 Press [q] to stop, [?] for help
 frame=  120 fps=0.0 q=2.0 Lsize=    3257kB time=00:00:05.02
 bitrate=5310.0kbits/s
 video:3182kB audio:58kB subtitle:0kB other streams:0kB global headers:0kB
 muxing overhead: 0.503110%
 }}}
 The output file shows no subtitles, {{{ffplay -sst 4
 oversized_pgs_subtitles.mkv}}} works fine.
 The following works as expected:
 {{{
 $ ffmpeg -i oversized_pgs_subtitles.mkv -filter_complex
 [0:4]scale=848x480,[0:0]overlay -qscale 2 -t 5 out.avi
 }}}

--
Ticket URL: <https://trac.ffmpeg.org/ticket/4781>
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