Wireless cameras are 1 area where the conversion to digital requires much bigger electronics. Long range FPV is still entirely analog. The only way to realistically get video from an indoor copter is an old fashioned analog NTSC camera, but synchronizing a camera to a monocopter, when you don't have access to a frame buffer or clock, remanes hard.

You can't synchronize the raw stream on the ground, because there are no longer ways to capture a raw frame buffer & modern MPEG encoders delay the stream.

The most likely solution is to have a LM1881 scanning for the vertical blanking interval in the composite signal. Then a dedicated microcontroller pulls the signal up or down to overlay a code on the right frame.

Software video overlay was done here: http://www.webx.dk/rc/video-wireless/video-osd.htm