Re: video signal transmission through two wire line through
1. If the tow-line is short (say, <50m) you may try to connect vide signal to one wire and video GND to the other wire, and that should be it ..
2. If it is longer (closer to 100m and more) you may consider treating it as a pair of wires and using a passive UTP-BNC video converters (go google) at both ends transmit video signal that way.
See: **broken link removed**
In both cases you may face attenuation of the higher part of the video signal (this will be first seen as weaker colour signal and then, if the losses are grater, B&W and loss of contrast – sharpness). If that’s the case you may need a video line driver (or receiver) that can compensate for these loses ..
Rgds,
IanP