[FFmpeg-user] Closed Captions in EIA-607 are broken

[W Boba]

Hi,

Can anybody confirm: is it a bug or it is something I'm doing wrong?

When I try to re-encode some MPEG2 TS files into h.264/mp4 using libx264 for encoder, embedded closed captions are not properly passed through to output file.

It looks to me like CCs are doubled for some reason.

command:
"ffmpeg.exe -y -v 99 -loglevel 99 -i sample-1min.ts -c:a aac -c:v libx264 sample-1min.mp4"

Original CCs (got them with CCextractor tool) look like this:
1
00:00:01,751 --> 00:00:03,469
        Yup, so you just
       want a nice layer.

2
00:00:03,536 --> 00:00:04,670
       That's good there.

3
00:00:04,721 --> 00:00:06,305
      Potatoes are ready.

4
00:00:06,372 --> 00:00:08,090
  This gets covered in
 your famous pot crack?


While extracted from MP4 file after re-encoding - they look like this:
1
00:00:01,234 --> 00:00:03,034
   So we'e're makaking B.C. h h?

2
00:00:03,036 --> 00:00:04,703
        YuYup, so you u just
       want a  nice layerer.

3
00:00:04,871 --> 00:00:06,004
       That''s goodod there.

4
00:00:06,105 --> 00:00:07,672
      Potatoes a are ready..

Tools:
CCextractor: https://www.ccextractor.org/
FFmpeg: https://ffmpeg.zeranoe.com/builds/win64/static/ffmpeg-20181018-f72b990-win64-static.zip
Source and output files, along with the FFmpeg debug log (240MB!) can be downloaded from:
http://64.137.230.232/cc-distortion.zip