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

Marton Balint cus at passwd.hu
Tue Sep 11 03:00:33 EEST 2018

On Sun, 9 Sep 2018, Devin Heitmueller wrote:

> 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.

Yes, just put the same value to both line 12 (or whichever line the user 
selects) and its pair line in the other field.

I am not worried about set top boxes or encoders, but other broadcast 
equipment (e.g: downconverters) working on uncompressed SDI. We 
hit this issue with product of a big vendor.


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