Anyone has used mark iv for live video with Blackmagic switch?
I have no problem using mark iii with Blackmagic TV Studio

I am wondering if mark iv is 1080i or 1080p from the hdmi port

Best accessory for an ATEM Television Studio is the Decimator MD-HX, which scales any format to the requisite 1080i the original ATEM switcher requires. The new version of the ATEM has a wide range of input choices but 23.98psf still isn't one of them (such as Sony cameras output), and all inputs have to be the same, so the MD-HX will remain indispensable for that and the other useful things it can do (SDI/HDMI cross conversion, 1x4 DA)