Unexpected signal interruptions for Blackmagic-Design devices

Symptoms of the issue

Even though your signal is stable, MovieRecorder would report some signal loss:

BMD Input: Error: Video input received a black frame (either the frame checksum is invalid or there is no incoming signal)
BMD Input: Warning: Video input is now receiving a video signal

Why does this happen? 

The issue happens with Blackmagic-Design drivers using driver kit (drivers 12.2 or later). Blackmagic-Design will be working on a fix.

Workaround 

The current workaround for this is to install drivers 12.1. (which are the last ones not to use Driver Kit)

Before doing it:

• Make real sure that your signal is really stable by routing it to a monitor or another way to confirm. It's best to confirm that this is your issue before trying some driver downgrade...
• Confirm that you can reproduce the issue with the current drivers.
• Make sure that drivers 12.1 will be compatible with your setup. 

Once you have verified that, then only downgrade the drivers and check if the issue persists.

Downgrading drivers to 12.1

Before installing drivers 12.1 - Apple Silicon

Drivers 12.1 still use an older system for drivers, based on kernel extensions (kext) instead of driver kit. This means that if you are using a computer with an Apple Silicon chip, you'll have to:
"Kexts must be explicitly enabled for a Mac with Apple silicon by holding the power button at startup to enter into One True Recovery (1TR) mode, then downgrading to Reduced Security and checking the box to enable kernel extensions. This action also requires entering an administrator password to authorize the downgrade." (extracted from this article: https://support.apple.com/guide/securit ... 54101b/web)

Once you have allowed kernel extensions to run, you can proceed with the downgrade to drivers 12.1.

Procedure for the downgrade

Here is the procedure:

• Run the uninstaller of the current drivers. Make sure to use the uninstaller of the drivers that are installed and not the uninstaller of the drivers you are installing.
• Restart the computer after the uninstal (even if it doesn't ask you to do so)
• Install the 12.1 drivers
• Restart the computer as instructed
• Do the firmware upgrade if prompted to
• If the card is not seen, go to "System Preferences > Privacy & Security" and allow the Blackmagic-Design extension to run.
• Restart the computer

Disclaimer

Again, it's a workaround, and we can not guarantee that it will work for you, and note that these older drivers may still have issues that were fixed since then. So make sure to test extensively before using this in production.