[FFmpeg-devel] [PATCH 0/5] Support for Decklink output of EIA-708 and AFD

Devin Heitmueller dheitmueller at kernellabs.com
Mon Sep 10 02:48:28 EEST 2018

On Sun, Sep 9, 2018 at 4:59 PM, Marton Balint <cus at passwd.hu> wrote:

> Thanks, I applied patches 1-4.
>>  decklink: Add support for output of Active Format Description (AFD)
> Regarding this one, I noticed you always set the AFD in line 12. Are you
> sure that it is OK to use line 12 for all resolutions?

12 should be fine at all resolutions, as it just needs to be at least
after the first line for switching (see ST 2016-3-2009 Sec 5).  I
already have a subsequent patch which makes the line configurable (as
well as for 708 and SCTE-104), but I am trying to avoid overloading
you with patches (which tends to result in *nothing* getting merged).

> Also, I think for
> interlaced formats you should set AFD for both fields, otherwise some
> equipment might scale/crop the two fields of a picture differently...

I've never seen a piece of equipment do such an incorrect scale/crop,
but I guess it's possible.  Part of the issue is that there are a few
different conditions in which it can vary between the two fields and
the way the underlying side-data is managed needs to be overhauled in
order to properly handle that case (e.g. the SEI can be on a field
basis in H.264, and we don't presently handle providing both values as
side data for the frame).

I think this patch handles the 99% use case (especially as PAFF
becomes less and less common),  Putting the same value on both lines
for interlaced formats is probably not a bad idea, although I suspect
in practice you're unlikely to run into equipment that has a problem
with it only appearing once.


Devin J. Heitmueller - Kernel Labs

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