[FFmpeg-devel] [PATCH] avcodec: add minimal teletext subtitle decoder

[Marton Balint]

On Sun, 14 Jun 2020, Paul B Mahol wrote:

> Nothing happened of this, so this patch should be merged.

What do you mean? Ass output support got added to libzvbi-teletextdec in 
2018.

Regards,
Marton


>
> On 4/26/18, Marton Balint <cus at passwd.hu> wrote:
>>
>> On Thu, 26 Apr 2018, Aman Gupta wrote:
>>
>>> On Thu, Apr 26, 2018 at 8:12 AM, Nicolas George <george at nsup.org> wrote:
>>>
>>>> Aman Gupta (2018-04-26):
>>>> > Another reason I discounted libzvbi is because it seems unmaintained,
>>>> > without a new release is over 5 years.
>>>>
>>>> Did the teletext standard evolve in the past five years?
>>>>
>>>
>>> I don't know, but there it is atleast one bug causing tests to fail on
>>> macOS which has been unfixed for 4 years.
>>>
>>> I managed to install libzvbi by hand and try it out. With `-txt_format
>>> text`, the generated output text is the same but without positions/colors.
>>> The ASS positioning code could be ported over, but it looks like
>>> vbi_print_page_region() strips out all the color information so there
>>> doesn't seem to be an obvious way to support text coloring.
>>>
>>> The zvbi decoder also hardcodes a (configurable) 30s end time per
>>> subtitle,
>>> which causes them to pile up on the screen and not disappear when they're
>>> supposed to. The logic from my decoder could also probably be ported over,
>>> under a new `-real_time 1` flag like I added to ccaption_dec last year.
>>>
>>> Here's a side by side comparison:
>>> https://dzwonsemrish7.cloudfront.net/items/2x1z3k0C0X3v0Z2j1F3b/teletext-sub-comparison.jpg
>>>
>>> I agree it would be ideal to have only one teletext decoder that works for
>>> everyone. However I'm done with my teletext project, and don't have time
>>> right now to redo all that work in the zvbi encoder. I also live in an
>>> ATSC
>>> region and don't use teletext myself, so I don't really care whether or
>>> not
>>> my decoder is merged into ffmpeg. I only shared it because some people on
>>> IRC expressed interest.
>>
>> I will try integrating the ASS formatting part of your patch to the
>> libzvbi decoder, and see how it goes.
>>
>> Regards,
>> Marton
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