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

[Carl Eugen Hoyos]

Am So., 14. Juni 2020 um 17:52 Uhr schrieb Marton Balint <cus at passwd.hu>:
>
>
>
> On Sun, 14 Jun 2020, Carl Eugen Hoyos wrote:
>
> > Am So., 14. Juni 2020 um 17:40 Uhr schrieb Marton Balint <cus at passwd.hu>:
> >>
> >>
> >>
> >> On Sun, 14 Jun 2020, Carl Eugen Hoyos wrote:
> >>
> >> > Am So., 14. Juni 2020 um 16:26 Uhr schrieb Marton Balint <cus at passwd.hu>:
> >> >>
> >> >>
> >> >>
> >> >> On Sun, 14 Jun 2020, Carl Eugen Hoyos wrote:
> >> >>
> >> >> > Am So., 14. Juni 2020 um 12:05 Uhr schrieb Paul B Mahol <onemda at gmail.com>:
> >> >> >>
> >> >> >> [...] this patch should be merged.
> >> >> >
> >> >> > I still believe this is one of the most important missing
> >> >> > features
> >> >>
> >> >> Which one? As far as I remember I integrated all the features (including
> >> >> colorized ass output) to libzvbi-teletextdec, so I am curious what is the
> >> >> feature that you still miss from that.
> >> >
> >> > You mean apart from the fact that this project was always about
> >> > re-inventing the wheel (like it or not)?
> >> >
> >> > Since this morning, I (very seriously) wonder if you have ever used
> >> > the existing teletext decoder (and how): Both "ffplay file.ts" and
> >> > "ffmpeg -i file.ts out.mkv" do not work as expected, and even if you
> >> > know that you have to specify "-txt_format ass" the output is still
> >> > completely unusable.
> >>
> >> Are implying that the default txt_page should be changed to "subtitle"
> >> from "*"? Beacuse that is all it takes to make it a regular subtitle from
> >> a list of all the pages (if that is what you mean when you write
> >> *unusable*)
> >
> > No.
> >
> > I am implying that FFmpeg needs an internal teletext decoder that
> > does not produce the specified graphical output as libzvbi allows
> > but decodes teletext to usable text subtitles (including automatic
> > page detection) without an external dependency (that we should
> > of course keep for the valid usecase of overlaying the intended
> > graphics).
>
> I kind of thought that havig something internal to ffmpeg was always
> justifed with something, e.g.: features, or speed, or licensing.

Historically (only) speaking, this is simply not the case.
(Although the speed argument can of course always be made,
including here.)

> I just don't see a distinctive reason here to do teletext decoding
> internally, so that is why I am against adding an internal decoder.

I believe that - on the contrary - having an internal decoder (with
arguably less features) would be an (in this case huge) advantage.

Most people probably agree that HDR is more important than
teletext subtitles but I have always considered this a particularly
important missing feature.

Carl Eugen