mgiardino wrote:WOuld this be connected via hdmi on the back of the board?
If you have an ATEM with HDMI connection you can directly connect a Raspberry PI HDMI output to the HDMI input on the ATEM. It's best to set the frame rates the same. Although most ATEM's have scalers and frame rate converters, for smooth animations (when using graphics or video) it's better to set the frame rate of the HDMI output of the Raspberry PI the same as the frame rate of the ATEM.
If your ATEM only has SDI inputs you would need an additional HDMI to SDI converter, e.g. from BMD.