Internal Keying

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Nick C

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  • Joined: Mon Oct 25, 2021 3:31 pm
  • Real Name: Nick Clarke

Internal Keying

PostMon Oct 25, 2021 4:19 pm

Hi All,

I'm working on some Teleprompting software (C++), which currently works correctly using external keying - however we also want it to have the option of internal keying.

I have changed the settings as per the documentation (which, as far as I can see, is simply changing 'true' to 'false' in the call to Enable, and changing the 'supported' checks from external to internal), and set up a test rig with an fairly old Decklink Quad card, using the first channel with the input on SDI pin 2 and output on pin 3. The card reports that it supports internal keying, and I get my teleprompt output on the SDI - however the background is black, not showing the source.

I believe that the rendering code is giving the correct alpha (it is initialising the whole image to all 0s, which I believe is correct for fully transparent black in BGRA8? I've tried setting the 'fill' to fully transparent, and it then appears black on the output exactly the same as the background), and I've checked that the input looks correct when captured directly to disk using FFmpeg.

Does anyone have any ideas what I might have missed? I'm assuming there must be another setting somewhere that needs to be different between the two modes? The SDK is not reporting any errors, which I presume it would do in the case of something like a format mismatch? I've tried both 1080p25 and 1080i50 sources.

This is using the latest SDK on Ubuntu.

Many thanks!
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Ian Morrish

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Re: Internal Keying

PostThu Oct 28, 2021 6:22 am

I don't believe the Old Decklink Quad v1 card supported internal keying (I know the duo Decklink card didn't although there was a way in CasparCG to get it to output key and fill on different channels - they would not stay in sync).
Some of the older devices also only support SD internal keying, even though they support HD capture or playback.
I know the SDI 4K and Decklink DUO 2 work with internal keying using the API.
Regards,
Ian Morrish
Video Integrated Scripting Environment
(Windows PowerShell with ATEM driver + more)
https://ianmorrish.wordpress.com
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Ian Morrish

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Re: Internal Keying

PostThu Oct 28, 2021 6:37 am

You can also test with the "Blackmagic LiveKey.exe" utility that you will find in the "C:\Program Files (x86)\Blackmagic Design\Desktop Video" folder.
Regards,
Ian Morrish
Video Integrated Scripting Environment
(Windows PowerShell with ATEM driver + more)
https://ianmorrish.wordpress.com
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Nick C

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  • Real Name: Nick Clarke

Re: Internal Keying

PostThu Oct 28, 2021 2:57 pm

Thanks Ian,

Ian Morrish wrote:Some of the older devices also only support SD internal keying, even though they support HD capture or playback


This was it - even though the card returns 'true' to the internal keying check, it only supports it in SD - and of course I was using HD! It worked when I passed it SD content. Fortunately our customer is using newer cards (8k Pro), and I should have access to one next week to confirm it works properly in HD on a newer card.
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Nick C

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  • Joined: Mon Oct 25, 2021 3:31 pm
  • Real Name: Nick Clarke

Re: Internal Keying

PostThu Nov 04, 2021 11:56 am

I've now tried it on another machine with an 8k card - and while it does work in HD, it is glitching terribly, and losing SDI sync every couple of seconds.

I'm wondering if this is related to the issue described in viewtopic.php?f=3&t=59162?

Is this known to still be a problem? The source is 1080 50i, and the output is going straight to a monitor. There's no glitching when I just get the card to pass through the input signal.

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