Internal decoder doesn't report invalid input for `dvbsub`

[MatthewAlner]

Hey! this is a really cool project exactly what I was looking for but i'm having some issues with the .ts files being produced by my HDHomerun. It seems like its only extracting the first line, in the json output I can see there is a lines array so I assume this should work.

[ecdye]

That's interesting, it almost seems like you might be comparing two different versions of the subtitle track and one has a little bit different layout.

Can you investigate and confirm that there is only one version of the subtitle track?

[MatthewAlner]

Looks like just the one to me Stream #0:2[0x102](eng): Subtitle: dvb_subtitle (dvbsub) ([6][0][0][0] / 0x0006)

ffprobe output:

➜  subtitle-test ffprobe travelMan.ts
ffprobe version 7.1.1 Copyright (c) 2007-2025 the FFmpeg developers
  built with Apple clang version 16.0.0 (clang-1600.0.26.6)
  configuration: --prefix=/opt/homebrew/Cellar/ffmpeg/7.1.1_2 --enable-shared --enable-pthreads --enable-version3 --cc=clang --host-cflags= --host-ldflags='-Wl,-ld_classic' --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libaribb24 --enable-libbluray --enable-libdav1d --enable-libharfbuzz --enable-libjxl --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librist --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libssh --enable-libsvtav1 --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox --enable-audiotoolbox --enable-neon
  libavutil      59. 39.100 / 59. 39.100
  libavcodec     61. 19.101 / 61. 19.101
  libavformat    61.  7.100 / 61.  7.100
  libavdevice    61.  3.100 / 61.  3.100
  libavfilter    10.  4.100 / 10.  4.100
  libswscale      8.  3.100 /  8.  3.100
  libswresample   5.  3.100 /  5.  3.100
  libpostproc    58.  3.100 / 58.  3.100
Input #0, mpegts, from 'travelMan.ts':
  Duration: 00:31:56.76, start: 1.400000, bitrate: 1661 kb/s
  Program 1
    Metadata:
      service_name    : Service01
      service_provider: FFmpeg
  Stream #0:0[0x100]: Video: mpeg2video (Main) ([2][0][0][0] / 0x0002), yuv420p(tv, top first), 544x576 [SAR 32:17 DAR 16:9], 25 fps, 25 tbr, 90k tbn
      Side data:
        cpb: bitrate max/min/avg: 3000000/0/0 buffer size: 1835008 vbv_delay: N/A
  Stream #0:1[0x101](eng): Audio: mp2 (mp3float) ([3][0][0][0] / 0x0003), 48000 Hz, stereo, fltp, 128 kb/s
  Stream #0:2[0x102](eng): Subtitle: dvb_subtitle (dvbsub) ([6][0][0][0] / 0x0006)

[MatthewAlner]

OK so I cut a little clip out of the show ffmpeg -i travelMan.ts -ss 00:05:10 -to 00:05:30 -map 0 -c copy travelMan_clip.ts

and its exhibiting the same behaviour as the whole so i'll share that here.

But actually looking at this in isolation, you can see it has all the words, just not in the right order

1
00:00:02,325 --> 00:00:02,225
place. I mean, these nice, little

2
00:00:02,325 --> 00:00:02,436
Love what they've done with the

3
00:00:05,125 --> 00:00:05,025
a bit there, never too much.

4
00:00:05,125 --> 00:00:05,236
centrepieces. You know, a bit here,

5
00:00:09,565 --> 00:00:09,465
I'd come and live here.

6
00:00:09,565 --> 00:00:09,676
If I was a bird,

7
00:00:11,845 --> 00:00:11,956
Would you? Yeah.

8
00:00:13,365 --> 00:00:13,265
and a lot of them do.

9
00:00:13,365 --> 00:00:13,476
If I was a bird that liked water

10
00:00:19,685 --> 00:00:19,796
Penguins. Look.

should be in this order

centrepieces. You know, a bit here,
a bit there, never too much.

If I was a bird,
I'd come and live here.

Would you? Yeah.

If I was a bird that liked water
and a lot of them do.

Penguins. Look.

Example for debugging => clip.zip

[MatthewAlner]

Ahh... I think this is just me not reading the manual.

Supported Formats

• PGS (.mkv, .sup)
• VobSub (.mkv, .sub, .idx)

it's a dvbsub 🤦🏻

my apologies, because it didn't throw and kinda worked I assumed it was supported.

[ecdye]

You're all good, I'm surprised that it worked as well as it did too. It must have been formatted in a way that made the decoder think that it was valid. When I have time I'll try and look into this more to see if I can figure out why it didn't fail and report it to the user.

You could try using the ffmpeg decoder option to see if it would work to process the subtitles. I haven't looked at this in a minute so I can't remember off the top of my head, but I think it should work decently well with any image based subtitles.