[FFmpeg-user] Forced Subtitles Only

[petesea at frontier.com]

OS: Fedora 14
FFMPEG: 2.5.3 (full version info below)

I'm trying to generate a vob (from dvd) that contains a subtitle stream 
into an mpeg2 with "hard" subtitles, but I only want to include the 
"forced" subtitles.

I'm able to generate an mpeg2 with hard-subtitles using the following 
command (see complete output below):

   $ ffmpeg -analyzeduration 250M -probesize 250M -i video.vob -filter_complex "[0:v][0:11]overlay" -codec:v mpeg2video -b:v 16384k -maxrate 30000k -bufsize 4096k -codec:a copy -f vob video-HARDSUBS.mpg

But it includes all the subtitles in the specified subtitle stream.  I 
only want to include the subtitles marked as "forced".  Is this possible 
with ffmpeg?

Using HandBrakeCLI (0.10.0) I can generate an mkv (h264) with forced-only 
hard subtitles using the same vob input file, so the information must be 
in the file.  Problem with HandBrake is it doesn't generate mpeg2 files, 
so I'd have to convert the mkv/h264 back to mpeg2 via ffmpeg.  I'm hoping 
to avoid that extra conversion.

------------------------------------------------------------------------

$ ffmpeg -analyzeduration 250M -probesize 250M -i video.vob -filter_complex "[0:v][0:11]overlay" -codec:v mpeg2video -b:v 16384k -maxrate 30000k -bufsize 4096k -codec:a copy -f vob video-HARDSUBS.mpg
ffmpeg version 2.5.3 Copyright (c) 2000-2015 the FFmpeg developers
   built on Feb 12 2015 12:31:33 with gcc 4.5.1 (GCC) 20100924 (Red Hat 4.5.1-4)
   configuration: --enable-gpl --enable-version3 --enable-nonfree --disable-static --enable-shared --disable-debug --enable-libass --enable-libfdk-aac --enable-libmp3lame --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-x11grab
   libavutil      54. 15.100 / 54. 15.100
   libavcodec     56. 13.100 / 56. 13.100
   libavformat    56. 15.102 / 56. 15.102
   libavdevice    56.  3.100 / 56.  3.100
   libavfilter     5.  2.103 /  5.  2.103
   libswscale      3.  1.101 /  3.  1.101
   libswresample   1.  1.100 /  1.  1.100
   libpostproc    53.  3.100 / 53.  3.100
Input #0, mpeg, from 'video.vob':
   Duration: 00:00:14.99, start: 0.500000, bitrate: 6305 kb/s
     Stream #0:0[0x1e0]: Video: mpeg2video (Main), yuv420p(tv), 720x480 [SAR 32:27 DAR 16:9], max. 9800 kb/s, 29.92 fps, 59.94 tbr, 90k tbn, 59.94 tbc
     Stream #0:1[0x80]: Audio: ac3, 48000 Hz, 5.1(side), fltp, 448 kb/s
     Stream #0:2[0x81]: Audio: ac3, 48000 Hz, 5.1(side), fltp, 384 kb/s
     Stream #0:3[0x82]: Audio: ac3, 48000 Hz, 5.1(side), fltp, 384 kb/s
     Stream #0:4[0x83]: Audio: ac3, 48000 Hz, 5.1(side), fltp, 384 kb/s
     Stream #0:5[0x84]: Audio: ac3, 48000 Hz, 5.1(side), fltp, 384 kb/s
     Stream #0:6[0x22]: Subtitle: dvd_subtitle
     Stream #0:7[0x20]: Subtitle: dvd_subtitle
     Stream #0:8[0x24]: Subtitle: dvd_subtitle
     Stream #0:9[0x25]: Subtitle: dvd_subtitle
     Stream #0:10[0x26]: Subtitle: dvd_subtitle
     Stream #0:11[0x28]: Subtitle: dvd_subtitle
     Stream #0:12[0x21]: Subtitle: dvd_subtitle
     Stream #0:13[0x23]: Subtitle: dvd_subtitle
     Stream #0:14[0x27]: Subtitle: dvd_subtitle
[mpeg @ 0x885bac0] sub2video: using 720x480 canvas
Output #0, vob, to 'video-HARDSUBS.mpg':
   Metadata:
     encoder         : Lavf56.15.102
     Stream #0:0: Video: mpeg2video, yuv420p, 720x480 [SAR 32:27 DAR 16:9], q=2-31, 16384 kb/s, 29.97 fps, 90k tbn, 29.97 tbc (default)
     Metadata:
       encoder         : Lavc56.13.100 mpeg2video
     Stream #0:1: Audio: ac3, 48000 Hz, 5.1(side), 448 kb/s
Stream mapping:
   Stream #0:0 (mpeg2video) -> overlay:main
   Stream #0:11 (dvdsub) -> overlay:overlay
   overlay -> Stream #0:0 (mpeg2video)
   Stream #0:1 -> #0:1 (copy)
Press [q] to stop, [?] for help
frame=  450 fps= 55 q=2.0 Lsize=    3628kB time=00:00:14.98 bitrate=1983.8kbits/s dup=94 drop=0
video:2755kB audio:819kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 1.519567%