How do i connect webcam to mac mini via an av splitter?

Hi guys, running a webcam to my tv's (upstairs and downstairs) via a 4 way av splitter box.

Now, id like to connect the cam to my mac so i can record motion etc. how do i do that? iv included the pics of the splitter and the back of my mac. Im guessing i need some kind of usb cable ??? but with the yellow and white connectors on the other end to attach to the splitter?

Any ideas what i need? or what its called? Thanks!