I am trying to convert an HDMI video signal (from my computer's graphic card) to SDI using an Ultrastudio 3D from Blackmagic.

I successfully converted an HDMI signal from my Canon 5D camera, but it does not work when I send a signal from my graphics card.

What is the difference between HDMI from a camera and HDMI from my GPU?

Edit

My goal is to send GPU generated content, not a film, so there should be no HDCP problems, am I right? So far I tried to sent my GPU output considering the Ultrastudio 3D as an extended desktop.