@ Moosa

If you are going with 4K NDI, then you will want the fastest CPU with the most cores.
I do not like the 12th Gen CPUs because their "efficient" cores have a base clock speed slower than vMix's recommendation of 3.0 Ghz or faster and only have one thread per core, which is of no benefit to vMix and should not even be considered when evaluating CPUs for use with vMix.
As such, the i9-12900K only has 8 "performance" cores, which is probably not enough to handle four 4K NDI cameras.

Just my 2 cents.


Ice

The info above is not accurate. We have 10 4K Birddog P400's with Full NDI going into an i9-12900K system no sweat, plus additional 4K NDI inputs (desktop captures, Premiere, etc.) and bunch of NDI outputs. Z690 motherboard with Resizable Bar enabled with an RTX A6000 (but something like a 3080 may be fine for you).

Your biggest issue by far will be bandwidth - you're going to need at least a 10Gbit connection going to that machine and a switch that handles that of course. We have 25Gbps fiber switch/NIC's. You could get by with a switch that has 1 Gb ethernet ports for the cameras, as long as that switch has at least 1 10Gb SFP+ port to a fiber NIC on the PC.

There are some other considerations, like your GPU, but it definitely is possible. And we could push it much further than what we're doing now.