CCExtractor version: Latest master branch

CCExtractor 0.91, Carlos Fernandez Sanz, Volker Quetschke.
Teletext portions taken from Petr Kutalek's telxcc
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CCExtractor detailed version info
        Version: 0.91
        Git commit: 5127da50d14655401c4086e39d8b2d7786c5038f
        Compilation date: 2021-07-28
        File SHA256: 713e7f8a6664cb4a8ce75c62e4e48ab7ce4566dcc6738faf03816b5c6725f889
Libraries used by CCExtractor
        Tesseract Version: 4.1.1
        Leptonica Version: leptonica-1.81.0
        libGPAC Version: 1.0.1
        zlib: 1.2.11
        utf8proc Version: 2.4.0
        protobuf-c Version: 1.3.1
        libpng Version: 1.6.37
        FreeType
        libhash
        nuklear
        libzvbi

In raising this issue, I confirm the following:

• I have read and understood the contributors guide.
• I have checked that the bug-fix I am reporting can be replicated, or that the feature I am suggesting isn't already present.
• I have checked that the issue I'm posting isn't already reported.
• I have checked that the issue I'm porting isn't already solved and no duplicates exist in closed issues and in opened issues
• I have checked the pull requests tab for existing solutions/implementations to my issue/suggestion.
• I have used the latest available version of CCExtractor to verify this issue exists.
• I have ticked all the boxes in this section and to prove it I'm deleting the section completely to remove boilerplate text.

Necessary information

• Is this a regression (i.e. did it work before)? Yes
• What platform did you use? Linux
• What were the used arguments? ./ccextractor -delay -1400 jeopardy-s37e99-srtissue.ts

Video links

• https://www.dropbox.com/s/ayrgx0xqfhljxho/jeopardy-s37e99-srtissue.ts?dl=0

Additional information

I recently noticed that when running ccextractor with negative -delay arguments, I get no output in the SRT file. This used to work for me without any issues. I ran a git-bisect to figure out which commit changed the behavior, and found it was this one:

#1167

I did a little debugging and found that nothing is being printed because of this if check in ccx_encoders_common::encode_sub

    sub->start_time += context->subs_delay;
    sub->end_time += context->subs_delay;
    if (sub->start_time < 0)
      return 0;

It seems the issue is that sub->start_time is always negative. Every time encode_sub is called, sub->start_time is decremented by 1400 (-delay -1400). Nothing else seems to be setting / modifying that value. If I comment out the if check, then I get correct output again.

I am happy to try submitting a PR to fix this, but I would need a little guidance on the intended behavior and what changes (if any?) would be desired.

Thanks!