Thank you for the response! Why didn't I think of that? The attachments do stick and get propagated to the CMVideoFormatDescriptionRef. And they do affect how AVAssetWriter converts to YCbCr. Thanks again!

Did you ever figure this out?

I'm having a little trouble with the Local Network security. I have a launchd daemon that is not able to access the local network. Daemons are supposed to be given access automatically, but this one is not. The problem may be that it is spawning another process, and that process is not getting the exemption. If I run the daemon command in a Terminal window it works as expected, with access given automatically.

For most Privacy & Security settings it's possible to manually set them using a configuration profile containing Privacy Preferences Policy Control (PPPC). The options listed include things like SystemPolicyDocumentsFolder and SystemPolicyNetworkVolumes. Is there an PPPC option that would allow us to add Local Network?