[mikegoelzer]

> I think it was not completely passive, but simple level conversion; DisplayPort is AC-coupled signal, HDMI is DC-coupled.

Wait, I don't think that's accurate. I've worked with HDMI/DVI and both are AC-coupled, that is, you put a 10 or 20 nF cap in series on the TMDS lines if you're driving directly from an FPGA's digital IO pins.