[FFmpeg-user] ffmpeg doesn't generate a ISO/IEC 14496-17 (MPEG-4 text) track when ingesting WebVTT subtitles to produce MPEGTS

[Daniel Andres Pelaez Lopez]

Hi everyone,

We are trying to create a mpegts with a ISO/IEC 14496-17 (MPEG-4 text)
subtitles track, using WebVTT, but seems like ffmpeg creates a ISO
13818-1 PES private data instead. The following is the ffmpeg command:

ffmpeg -i subtitle.vtt -c:s mov_text -f mpegts output3GPP.ts

And the following is the output of the ffprobe for that file:

Input #0, mpegts, from 'output3GPP.ts':
  Duration: 00:00:19.00, start: 1.400000, bitrate: 1 kb/s
  Program 1
    Metadata:
      service_name    : Service01
      service_provider: FFmpeg
  Stream #0:0[0x100]: Data: bin_data ([6][0][0][0] / 0x0006)
Unsupported codec with id 98314 for input stream 0

However, if we generate a mp4, it works, the following is the command:

ffmpeg -i subtitle.vtt -c:s mov_text -f mp4 output3GPP.ts

And the following is the output of the ffprobe for that file:

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'output3GPP.ts':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2mp41
    encoder         : Lavf57.83.100
  Duration: 00:00:20.00, start: 0.000000, bitrate: 0 kb/s
  Stream #0:0[0x1](und): Subtitle: mov_text (tx3g / 0x67337874), 0
kb/s (default)
    Metadata:
      handler_name    : SubtitleHandler

Any reason why both commands behave differently? is mpegts not
supporting ISO/IEC 14496-17 (MPEG-4 text)?

Note: attached is the subtitle.vtt file.

Regards


-- 
Daniel Andrés Pelaez López
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