I'm trying to find a good way to transmit two video images using one transmitter, like the BlackBird 2 does, but with my own choice of cameras (so I can use a shorter focal length + mount them much farther apart).  I'll be digitizing the image eventually, but transmitting it over 5.8.

Is it possible to remove the cameras from the BlackBird 2 board and attach wires from other cameras in their place?  Is there a simple piece of electronics I can use to take two inputs and interlace them?  My Google-fu is weak on that subject.  I'm mostly a software guy - so while I know that building electronics from scratch to interlace a couple of composite signals is possible, anything past soldering is a bit beyond me

Thanks!

"mostly a software guy"

Indeed.

The signal from an FPV camera is an analogue, interlaced PAL or NTSC television standard video signal. The VTX sends this analogue signal via frequency modulation over a 5.8GHz carrier wave, just like old fashioned analogue TV, but on a different frequency and with less bandwidth.

The input to a VTX is an analogue signal. You won't be sending anything in digital through a VTX. It's not designed for it and the transmission mechanism is not capable of sending very high bitrate digital data.

The Blackbird 2 stereo camera does its magic by compromising on frame rate and resolution. It either interlaces the two cameras into one signal for a device capable of decoding field sequential 3D, dividing the 60Hz interlaced picture into two half resolution 30Hz signals. Or, it uses its specialised hardware to halve the resolution of each image and combine them into one video frame for side by side modes.  You simply can't fit more into the limited bandwidth of a 5.8GHz analogue video channel. The Blackbird only provides NTSC, not PAL and this is because of the higher refresh rate with NTSC and the lower resolution. In the end, it's still analogue video.

If you want to send high resolution digital video through the air, you need to look at dedicated solutions like the Connex Prosight. It, and similar systems, use 5GHz WiFi on multiple bands to send the video signal. Range is shorter, equipment is larger and more power hungry and cost is orders of magnitude higher. Latency is more than 100ms.

tl;dr

You can't do digital data over an analogue video system.

Sorry!  I don't think I explained my use case very well.  I'm very happy to sacrifice quality and resolution.  I want it analog because I need better range than wifi will give me.  Interlacing it is a tradeoff where I give up quality in exchange for better weight and power consumption: I really don't want two antennas.

Digitization happens strictly at the receiver end, so I can pipe it through an existing software project that takes wide-FOV input and displays a much smaller-FOV viewport. It's for quick client-side head tracking and stabilization even with a slow camera gimbal.  Experimental (read: it really sucks but it's a pet project I'm invested in); usually I can do wifi because I'm indoors.

The reason I brought that part up at all is because, yeah, normally I'd use digital cameras and process the images locally before transmitting over wifi.  But since I need the benefits of 5.8GHz analog, and there's already systems that transmit two video signals over the same analog stream, I was hoping to skip the RPi and use existing hardware as much as possible.  That would also mean huge lag benefits, since the digitization and processing is happening on a much faster machine.  Absolute worst case though, I guess using digital cameras, processing on the drone, and then outputting into analog for transmission isn't the end of the world if there's no other option.

The Blackbird 1 allows the two cameras to be separated by up to 2000mm and only generates field sequential 3D.

http://www.robotshop.com/en/blackbird-1-...amera.html

This would appear to solve your need to position the cameras further apart. I'm sure you can experiment with different lenses on the cameras to use a different focal length - the lenses are standard M12 thread.