@tlaloc

Performing some thread necromancy because I'm so excited that the next public release will (finally) include a way to do this (among many other things) 

@ray

Dual graphics cards is unsupported (meaning we are unable to provide tech support) since we have no way to create the same/similar setup.

With that said you can use more than one card. 
What is important is that you don't share/mix video from one output path to another.

So if you:

1.  add a movie player, and connect its output to stage 1 (using gpu1)
2. add a movie player, and connect its output to stage 2 (using gpu2)

Don't try to mix the two videos together in any way.. keep them separate. Mixing will require moving the texture from one gpu to the other, and will be a spped/bottleneck.

No Isadora allows you to move video in anyway you like, so its very flexible. If you can keep the video flow simple, and maintain individual paths, you can make it work very well.

TEST, TEST, TEST!

Start simple, and build up.. test constantly

@opmeyer1

I am recording this as an issue we need to investigate. Thank-you for the report.

Thanks for all of your suggestions. The datapath looks great but is beyond my budget. Please excuse my lack of knowledge but what type of output ports does the Blackmagic Decklink have and can I use an adapter to change them to HDMI? As far as multiple graphic cards on windows goes, I just slapped them in and they  worked. Dumb luck?

@opmeyer1

Hi! 

Thanks for making such a detailed bug report. Tagging our team here to log the bug report / get that into our system.

@woland @dusx

Hi Isadora team — short bug report and recommended fix for matching input signal pixel formats to capture setting pixel formats UltraStudio 4K Mini HDMI RGB/YUV feeds.

Problem (symptoms): When Isadora opens the Blackmagic driver the device is forced into YUV 4:2:2 input mode, producing a black preview even though the incoming HDMI signal is present at 1080p60 RGB 10‑bit. Launching Blackmagic Media Express immediately reconfigures the device to RGB10 and the image returns.

Possible root cause: Isadora is calling the Desktop Video API without negotiating or selecting the correct pixel format/display mode (or is explicitly requesting a YUV pixel format). The Blackmagic driver will accept an explicit RGB10 request or perform auto‑negotiation if asked; currently Isadora’s call path forces YUV.

Recommended fix 

1. Negotiate display mode + pixel format on open — call the Desktop Video API to enumerate supported display modes (GetDisplayModeIterator / display mode list) and choose the exact 1080p60 mode reported by the device.
2. Request RGB10 explicitly when available — call EnableVideoInput (or equivalent) with the matching display mode and bmdFormat10BitRGB (or the SDK constant for 10‑bit RGB).
3. Expose a UI override — add a simple capture setting: Pixel Format: Auto / Force RGB10/ Force RGB8/ Force YUV422 for troubleshooting and edge cases.

I personally did up to 10, using a Blackmagic Decklink Quad (8 Outputs), and two HDMI ports (control monitor / additional monitor for the backstage crew)

With a RTX 4090, and a speedy CPU you should be able to push that to do a Blackmagic Decklink + a Datapath FX4.

@ray said:

I already have an rtx 4090 and an rtx 3070 installed

@DusX Could you please provide advice about working with multiple graphics cards on Windows? 

I always forget if this is a no-no or something that's fine to do after some specific configuration.

@skulpture said:

Get a datapath FX4 or similar. It takes a single 4k input and splits it into quads; then you get 4 individual FHD outputs.https://www.datapath.co.uk/dat... 

 This would be my suggestion as well

@ubik

Can you send the patch either here (if you're comfortable) or in a support ticket (see the link in my signature) so we can take a look at it? In medical terms, it can be hard to diagnose a patient over the phone rather than through a physical exam.