Decklink Video Tearing

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jolson
Met Resolume in a bar the other day
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Decklink Video Tearing

Post by jolson »

Our setup is as follows:
  • Video wall (3840 x 1080) via two controllers running at standard 1080 resolution, split into a left and right half
  • Resolume (composition 3840x1080). Advanced output to 2 screens - SDI outputs on a BMD Decklink Duo card (latest drivers). Also tried outputting across two different Decklink duo cards with similar results.
  • Genlock from an external source, verified genlock using Blackmagic Desktop tool.
  • Output goes into two LED wall controllers running 1080.
Visible tearing across the left/right content. Tested with both mp4(h264) video content, as well as Resolume generated "Line Scape" content. Sometimes the left half of the screen is a frame head, sometimes a frame behind, and sometimes in perfect sync. Most noticeable with "strobing" content (high contrast single frame content).

Any thoughts would be appreciated.

Zoltán
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Re: Decklink Video Tearing

Post by Zoltán »

Decklink outputs are not guaranteed to be in sync.
Resolume passes the texture to the BMD drivers, and then it's up to the driver to display it.
If it's a consistent delay, try adding a little bit of delay to the BMD screens in the Advanced output.
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jolson
Met Resolume in a bar the other day
Posts: 13
Joined: Sun Jun 19, 2022 17:33

Re: Decklink Video Tearing

Post by jolson »

The delay is inconsistent. What SDI output device would provide better sync for edge blending.

Thanks!

Zoltán
Team Resolume
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Re: Decklink Video Tearing

Post by Zoltán »

I'd do a single GPU output +datapath fx4 (or Quadro) and use SDI converters.
Software developer, Sound Engineer,
Control Your show with ”Enter” - multiple Resolume servers at once - SMPTE/MTC column launch
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Arvol
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Re: Decklink Video Tearing

Post by Arvol »

BMD is pure rubbish. IF you get the right magical sequence of driver installers to get the cards working, they do not share a clock and you WILL get tearing. Look into an AJA Corvid line card.

jolson
Met Resolume in a bar the other day
Posts: 13
Joined: Sun Jun 19, 2022 17:33

Re: Decklink Video Tearing

Post by jolson »

Upgraded to a AJA Kona 4 (cannot find a Corvid anywhere). Definately seen an improvement, but still experience tearing. Using both internal and external reference (tri-level for 1080i59.94)

jolson
Met Resolume in a bar the other day
Posts: 13
Joined: Sun Jun 19, 2022 17:33

Re: Decklink Video Tearing

Post by jolson »

Arvol wrote: Mon Jul 18, 2022 17:58 BMD is pure rubbish. IF you get the right magical sequence of driver installers to get the cards working, they do not share a clock and you WILL get tearing. Look into an AJA Corvid line card.
AJA is extremely backordered, but I was able to get my hands on a AJA Kona which is also Resolume certified. Still seeing noticeable tearing. Any thoughts?

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Arvol
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Re: Decklink Video Tearing

Post by Arvol »

You are getting tearing because you have 2 inputs on a single canvas and the 2 inputs that are driven into those 2 separate processors are not sharing the same clock source (You can genlock the processors but the input from the source isn't locked).
You need an output device that has a shared clock across all of it's outputs. A Quadro card has this and the Corvid line from AJA has this. I can't comment on Kona as I know nothing about it. BUT, if your outputs are not sync'd (sharing the same clock) you will get tearing, regardless of the brand.

jolson
Met Resolume in a bar the other day
Posts: 13
Joined: Sun Jun 19, 2022 17:33

Re: Decklink Video Tearing

Post by jolson »

Just to close the loop on this, after a long delay I was able to replace the Decklink Duo cards with a single Decklink 4k, and to no surprise this solved the tearing issue. However, to get it them to two different video processors was a bit of a hack but it works -- basically taking a 4k HDMI to SDI demuxer (outputs 4x SDI-3G HD) and then sending the respective quadrants to the correct video wall processor. Next on the list will be to get a single processor that can simply take the 4k input natively without having to do this demuxing bit.

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Arvol
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Re: Decklink Video Tearing

Post by Arvol »

If your LED is running Nova, grab a Nova H2 fully loaded for under $10k and you should be set.

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