[FFmpeg-devel] [PATCH v2 1/2] libavformat/mpegts: Extract arib_caption descriptor data into codecpar->extradata

[Jan Ekström]

On Sun, Apr 11, 2021 at 6:17 PM zheng qian <xqq at xqq.im> wrote:
>
> Consider the remuxed stream could be handled by other clients rather
> than FFmpeg,
> e.g. I'm working on HTML5 playback for ISDB television with ARIB
> captions through
> mpegts.js + b24.js/aribb24.js. Other ISDB TV clients may also have
> possibilities to
> check these fields, probably.
>

I don't think anything I have noted so far has made the remuxed
streams any more invalid than what your patch ideas have been? I mean,
that is the base idea - to make sure what we are generating is valid.
Just that you can already grasp the component tag and
data_component_id ranges/values from the ARIB caption profile already,
without having to copy the structure wholesale. component tag happens
to be what is exposed by AVStream::stream_identifier already at this
point, so if re-use of this value is wanted, that can be attained
through other purposes.

That is, unless there are other structures in the stream which have
references to the component_tag bit (which as far as I can tell is the
only changing bit in addition to additional_arib_caption_info, which I
went through). That said, if there are references to this value in
other streams or data structures, we are *not* copying those around,
so those would have to be implemented if that is so.

In other words, at this point the only thing explicitly required by
the muxer (albeit dummy values can be inserted if really needed) seems
to be the stuff within additional_arib_caption_info.

Jan

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