[FFmpeg-devel] [PATCH] lavc: Replace 181 magic number with ITU_T_T35_COUNTRY_CODE_US

[Tomas Härdin]

mån 2025-03-03 klockan 08:55 -0500 skrev Devin Heitmueller:
> On Mon, Mar 3, 2025 at 7:25 AM Tomas Härdin <git at haerdin.se> wrote:
> > 
> > Looking at CTA-708 at the moment and noticed this. In the future we
> > might want to make it possible for the user to set the country
> > code.
> > This patch makes finding usage of the US country code easier
> 
> I've got no objection to moving a constant value to a #define for the
> purpose of clarity, but there should never be a reason it needs to be
> configurable by the user.  The country code to be used for CTA-708 is
> defined by the standards authority and must be 0xb5 (just as the
> provider code must be 0x31).

So it's "US" even if something is broadcast in Sweden? T.35 has a whole
list of countries, some of which don't exist any more, and some new
ones are missing

> Even if the captions are intended to
> serve other countries, the country code will stay the same (defining
> the country code for individual languages goes in the PMT).

How is one supposed to mux multiple subtitle languages in MPEGTS +
H.264 anyway? This isn't clear at all from what I've read. Country
codes, as opposed to language codes, being used in the 708 SEI makes it
worse. And what of other container formats that have no PMT?

/Tomas