How do I capture video in real time from a Canon 5D Mark II to iMac in Final Cut Pro? We really need your help.

We are shooting a movie and searching for a solution how to capture video from HDMI port of Canon 5D Mark II to an iMac 27 inch in real time. The iMac doesn't have an HDMI port. We have a Mini DisplayPort to HDMI adapter, but it's not bidirectional so we can't use Mini DisplayPort for input.

Is there any way to capture video in our case? Are there other adapters that are bidirectional or something else?
You may be able to use the Log and Capture window (File>Log and Transfer):


However, this requires you to hook up the camera in such a way that Final Cut Pro recognizes. IIRC, the Canon 5D Mark II doesn't have a Firewire cable. The HDMI capture card might work, as long as FCP recognizes it.