[FFmpeg-devel] [PATCH v3 1/1] avformat/mpegtsenc: Write necessary descriptors into PMT for arib_caption muxing

[zheng qian]

On Tue, Apr 20, 2021 at 6:46 AM Jan Ekström <jeebjp at gmail.com> wrote:
>
> On Tue, Apr 20, 2021 at 12:11 AM Marton Balint <cus at passwd.hu> wrote:
> >
> >
> >
> > On Mon, 19 Apr 2021, zheng qian wrote:
> >
> > > Is there anyone who could review this patch?
> >
> > Jan was interested in this, so preferably he should also comment, but it
> > looks fine to me.
> >
>
> OK, this explains why I didn't see my response on patchwork.
> Apparently he had CC'd me and thus the "reply" button in gmail sent an
> e-mail directly to him and I was hurrying due to being on a lunch
> break -_- (and thus didn't notice).
>
> In any case, I did some comments and am now waiting for a second
> opinion regarding the usage of stream_identifiers in the ARIB context.
> After all, the specifications do let one utilize 0x30-0x37 for profile
> A/full-seg ARIB captions, so there must be a reason for them to not be
> as limited as profile C/1seg to a single identifier :)
>

I've found related definitions in ARIB TR-B14, Fascicle 1, 4.2.8.1
and you can find it in
http://web.archive.org/web/20160319090430/http://arib.or.jp/english/html/overview/doc/8-TR-B14v2_8-1p3-2-E2.pdf

4.2.8.1 section says:
"However, for component tag values of default ES of caption,
set 0x30 or 0x87, for component tag value of default ES of
superimpose, set 0x38 or 0x88."

That means 0x30 is considered as the default value for
Profile A caption ES. The section didn't describe how to
utilize other values rather than 0x30 in the 0x30~0x37 range,
and due to the second language caption is designed to be
multiplexed in the same ES, seems that it's assumed that
there will be usually only one ARIB caption within a program.

Anyway, I have never seen a TS program that carries 2 or more
arib_caption streams among Japanese TV channels.
Even if we manually try to remux 2 or more arib_caption streams
into a TS program and both use the component tag of 0x30,
it shouldn't cause any playback problems.

Best regards,
zheng qian

> Jan
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