I'm trying to create a small project where I have 2 composite video outputs and 1 monitor.
To switch between the 2 sources (no sound - only the yellow video cable), I was thinking using the relay module (https://www.espruino.com/Relays) and connect it as:
Output to monitor: K1 Pole
Output from source 1: IN1
Output from source 2: IN2
Ground / shield from the 3 cables would all be connected.
Could I've use the relay module to handle the video signal or would the module generate to much noice?
I tried a similar sort of thing using a multi-pole switch, I switched the ground wires as well, it worked but there was a flash and the image was distorted momentarily after switching, the image kind of wobbled and vibrated for a second or two. Then the image was ok, there was no noise after the image had settled down but it didn't seem like it was doing the monitor any good so I used to turn the monitor off during switching as a precaution.
I suppose the electro-magnetic coil in the relay would interfere with the signal wire, could you wire it so the signal wire uses the normally closed position so the relay is not energised when the signal is connected?
Analog TV studios used a master framing source for all their equipment so that the composite video frames were synchronized. Without that synchronization, switching video sources causes the monitor to resync to the new source and in the process the picture gets scrambled until it locks to the new sources framing pulses.
NTSC signal explanation:
Part2 Color Burst
Here's someone who appears to have done it.
I'd say using a relay would be fine - you will get a flash/gitter because the monitor will have to resync to the slightly different framerate, but that really shouldn't cause any damage at all.
At the end of the day, it's not that different from just using a physical switch to swap over the composite inputs.
Thanks for all your replies- I have to give it a try to see how it works in real life.
After googling a bit I've found this: https://www.engadget.com/2007/03/13/how-to-make-a-solid-state-a-v-switcher/
I have no idea if that would prevent the flash/glitter, but within the next days I'm gonna test the switch... - and after that the IC from the link...
Edit... just a small thought- it's the exact same camera the 2 sources. They are just pointing in 2 different directions - would that make any change in the synchronization?
I suspect that each camera generates its own sync signals. High end cameras have sync inputs and outputs. Have a look at the camera specifications to see if your cameras have this capability.
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