GoPro FPV Setup (cables)

Output cable is: 2.5mm 4-pole jack
From inside, connections are: ground, video, audio, unused
yellow: video with shield (ground) , white: audio with shield (ground)
connecting to servo plug:

• two grounds together, to servo black ("ground")
• video, to white/bronw ("signal")
• audio: to red ("power")

Two versions of off-the-shelf cables from ReadyMadeRC:

• generic a/v
• immersionRC specific

Nice tutorial from RCTestFlight: