Looking to build a remote video trigger

Hi!

I'm working to assemble a remote camera system, and am trying to figure out how to remotely trigger video using a wired connection on the Nikon D3200 (or similar) type camera. I see lots of traditional cable releases for stills, but I can't seem to find a pin out for the video trigger. I already have an array set up using GoPro's, so once I add the DSLRs it will be awesome!

thanks for the help!

Matt