[FFmpeg-devel] [PATCH v3 1/6] avcodec/mpeg12dec: extract only one type of CC substream

[Marth64]

>Is it not possible to extract all of them simultaneously?

Each of the extractable CC bitstreams would need to be exposed as an
independent eia608 AVStream, because each represents a distinct stream.
They can’t be commingled (which is what this patch addressed). I’m not sure
of a way to sanely present multiple eia608 streams to the end user.
AVStreamGroup gives me hope for the future, but I can’t think of a
technique in present day.

This is because: as it stands now the only way I know of to open a context
on an mpeg2/h26x source with an eia608 AVStream exposed is via the lavfi
movie=in[out+subcc] technique - but that only exposes one stream.

I guess the subcc keyword in the filter can be expanded to expose multiple
bitstreams, even via AVStreamGroup, but user would have to be aware and
opt-in. Otherwise it could get confusing. How would the user easily know
which bitstreams are in the source file? We can probe this to some extent,
but what if the eia608 bytes don’t show until halfway through the source?

Open to ideas, thoughts, as I’m gathering my own on this in a notebook over
the past few weeks.

Respectfully,
Marth64