I would think its because of HDCP…..Mac’s typically output HDCP unless told not to, and HDCP can’t be passed through SDI. There for the computer is like, nope, im not outputting video because the switcher i am going to is not HDCP compliant.
Hoping you will actualy get this, – I was reading a post by you paulo where you refereed to a link that was a genlock tutorial – It was found here – https://paolociccone.com/archives/36
This page is now defunct, but i am really intereseted in the information… If theres anyway you can help out that would be great..