BlackMagic Decklink Alpha Key output

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erzyk
Met Resolume in a bar the other day
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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
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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?

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Oaktown
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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?

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Oaktown
Resolume honorary member
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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).

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