I can get a single SDI output on the Decklink quad but it does not give me the option to set an alpha key output. Why would this be different from a Decklink duo? Perhaps I am doing something incorrectly? I am running a MBP Retina Yosemite with the card in a Sonnet Echo Express III TB expansion. I can access all four outputs with the BMD software, so I know the card and cage are working. Everything is updates to the latest rev.
Connected to the Decklink quad, it would not provide that as an option.
@CSP Please make sure that you have correctly configured the ports for output in the Blackmagic Desktop Video Setup app.