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

[Paul B Mahol]

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

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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