BlackMagic Decklink Alpha Key output

Post your questions here and we'll all try to help.
Post Reply
erzyk
Met Resolume in a bar the other day
Posts: 5
Joined: Fri Nov 16, 2018 13:19

BlackMagic Decklink Alpha Key output

Post by erzyk » Fri Nov 16, 2018 13:33

Hi,
I would like to ask if it is possible and how to output a full broadcast feed from Resolume over one BlackMagic DeckLink card. The thing is that all the newer cards supports RGBA or YUVA internal buffer inputs and outputs them on two SDI links: Out A is Fill and Out B is Key (only alpha channel).
I found methods in this forum telling to create a separate output with "Is Key" option, but this makes it impossible to use one card instead of two separate cards or a Duo card.

Is it feasible to use the full features of a BMD card and make use of the A and B outputs on newer cards for Key+Fill outputs? This would additionally avoid any delay between Key and Alpha.

Thanks in adevance

Joris
Doesn't Know Jack about VJ'ing or Software Development and Mostly Just Gets Coffee for Everyone
Posts: 5180
Joined: Fri May 22, 2009 11:38

Re: BlackMagic Decklink Alpha Key output

Post by Joris » Mon Nov 19, 2018 15:51

So these cards don't have two assignable outs, but are hardwire to send out the key on a fixed second SDI port? Do you have a link to one of these cards?

User avatar
Oaktown
Resolume honorary member
Posts: 2790
Joined: Tue May 08, 2012 15:19
Location: Oakland, CA

Re: BlackMagic Decklink Alpha Key output

Post by Oaktown » Mon Nov 19, 2018 17:19

Currently the following Blackmagic capture devices support Key/Fill output:
  • Decklink 4K Extreme / Extreme 12G / Pro
  • Decklink Duo 2 / Quad 2 (see additional configuration steps below)
  • UltraStudio 4K / 4K Extreme / 4K Extreme 3 / HD Mini
The Decklink cards can be used for generating fill and key output but I don't believe any Blackmagic Decklink card supports RGBA/YUVA on either input/output side.

As far as I know, the 4:4:4:4 support is on UltraStudio hardware for file playback only.

erzyk
Met Resolume in a bar the other day
Posts: 5
Joined: Fri Nov 16, 2018 13:19

Re: BlackMagic Decklink Alpha Key output

Post by erzyk » Fri Dec 14, 2018 14:43

@Joris - The newer Decklinks can output Fill/Key over 2 SDIs. The hardware is taking RGBA or YUVA input buffers and is splitting it into 2 SDI streams - one fill and one key for external keying/compositioning.

@Oaktown - now I have no access to my Resloume PC to test it, but do you mean that doing a screen output to one of the mentioned BMD cards will automatically generate two SDI (key + fill) streams without checking the "is key" option?

User avatar
Oaktown
Resolume honorary member
Posts: 2790
Joined: Tue May 08, 2012 15:19
Location: Oakland, CA

Re: BlackMagic Decklink Alpha Key output

Post by Oaktown » Fri Dec 14, 2018 17:41

@Oaktown - now I have no access to my Resloume PC to test it, but do you mean that doing a screen output to one of the mentioned BMD cards will automatically generate two SDI (key + fill) streams without checking the "is key" option?
Correct but in order for the blackmagic card to generate the key, you need to be able to output a signal with alpha (straight or premultiplied).

Isse
Met Resolume in a bar the other day
Posts: 7
Joined: Mon May 21, 2018 09:38

Re: BlackMagic Decklink Alpha Key output

Post by Isse » Sun Oct 06, 2019 23:25

The UltraStudio 4K is found by Resolume as a single device, you can not dedicate SDI A as one monitor and SDI B as another and due to this it won't work. I've spent days trying to figure this out and my findings are:

The US4K as 1 monitor out with 2 slices and one of which has "is Key" enabled in advanced on the output tab of one of the slices. Here is the thing, this look correct in Resolume as you have the bottom slice as alpha and the top slice as the viewable Fill but it still goes out on 1 output. There is no config available to split the 2 chanels over the 2 SDI outputs and as the signal goes out equal summed and ready, Key & Fill don't work as it should. Premultiplied, straight doesn't matter as far as I know.

I used both my BMD Mini Monitor and that worked with perfect result as I could config them as 2 outputs where I set one as the "is Key" which I summed in the switch but there was sync issues. When I did the same with 2 US4K units and synced then on ref input is worked like a charm. But still thats just bloody anoying to use 2 US4K for a simple task like that.

So basically the Resolume team have to add the feature to set up SDI output on units like the Ultrastudio rack decks if this is to be done by a single unit :-(

Post Reply