[FFmpeg-devel] [PATCH v4] avformat/mpegtsenc: enable muxing of ARIB captions

[Jan Ekström]

On Mon, Jun 7, 2021 at 8:09 PM Jan Ekström <jeebjp at gmail.com> wrote:
>
> From: zheng qian <xqq at xqq.im>
>
> Writes a general ARIB stream identifier descriptor, as well
> as a data component descriptor which also includes a
> pre-defined additional_arib_caption_info structure.
>
> Signed-off-by: zheng qian <xqq at xqq.im>
> ---

For the record, I did and do think that counting and limiting the
amount of ARIB caption streams per program would be technically more
correct, but since:
1. In most cases you will only have a single stream in your input of a
given profile (as multi-language subtitles are supposed to be handled
in the same PID).
2. it seems like a pain as mpegtsenc does not have existing
infrastructure for these sorts of checks as nothing else is limited in
stream count per-program.

I decided that utilizing the default identifier (0x30, 0x87) for all
such streams is Good Enough for an initial implementation. For Profile
A streams values are available until 0x37, but effectively only
permitted for secondary renditions (multi-view etc). Profile C only
permits a single identifier - 0x87.

As changes compared to v3:

1. I have split the descriptor writing into its own function, as
mpegts_write_pmt is already long enough.
2. Checked references and adjusted some comments as well as the commit message.

Jan