There is a history of issues with macOS and Radeon Pro VEGA graphics cards when the system's desktop outputs are used with non-HDCP compliant devices. Currently this is not something we have seen on Windows machines, but we have seen issues with most Macs that are using a VEGA GPU. Specifically, we have seen issues with the entire OS freezing during use with any apps using an HDMI graphics output from the computer that is not HDCP compliant (HDMI converters to SDI or Cat5/6 extenders are inherently not HDCP compliant). This does not affect Blackmagic video outputs.
Which macs are affected?
iMac Pros and any other Mac with a Vega GPU
How can I find out if my machine has this card?
Click the Apple Logo at the top left of your computer screen, and then select "About this Mac". In the About this Mac, you can view next to "Graphics" and it tells you which GPU is installed on this machine.
What are our recommendations?
We recommend that if you are using one of these machines with a Vega GPU to not use direct HDMI outputs as this is the cause of the freeze. We recommend going direct SDI out with a supported DeckLink device, or one of the UltraStudio series devices. A list of the supported devices can be found here under the Alpha Keyer and SDI headings.