Re: [FFmpeg-devel] [PATCH] libavcodec/mpeg12dec.c: rename 0x0502 CC format

[Kieran Kunhya via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

On Sun, 26 Jan 2025, 00:31 Soft Works, <softworkz-at-hotmail.com@ffmpeg.org>
wrote:

> > -----Original Message-----
> > From: ffmpeg-devel <ffmpeg-devel-bounces@ffmpeg.org> On Behalf Of
> > Marth64
> > Sent: Sunday, January 26, 2025 1:14 AM
> > To: FFmpeg development discussions and patches <ffmpeg-
> > devel@ffmpeg.org>
> > Subject: Re: [FFmpeg-devel] [PATCH] libavcodec/mpeg12dec.c: rename
> > 0x0502 CC format
> >
> > > they are broadcasting using a variation of DVB-S (there is no US
> > standard for sat tv), so the current naming is actually valid.
> >
> > This is my understanding also, but I do believe there was 1 other
> > network that used the same variation.
> > Hence why I suggested a generic name. The counter argument from
> > Kieran
> > was that it's not a DVB standard either so DVB 0502 not a great name.
>
> It's "user data", so there doesn't necessarily need to be a standard. It's
> inconsistent anyway:
>
> SCTE-20 (5.7) defines a single byte:
>
> "user_data_type_code—An eight-bit code for picture user data, 0x03"
>
> while ATSC/A53-Part 4 (6.2.3) mandates a
>
> "user_data_identifier – This is a 32 bit code"
>
> Which is supposed to be registered with SMPTE:
>
>
> https://web.archive.org/web/20150324170029/http://www.smpte-ra.org/mpegreg/mpegreg.html
>
> Then followed by 03 as type code.
>
> (this aligns with the implementation)
>
>
> I haven't found the corresponding in the DVB specs, it must have a
> different name there.
>

DVB (TS 101 154) mandates a particular way of transporting captions (that
the Dish method predates). There are other operators that do their own
thing too.

Kieran

>
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