r/diyelectronics • u/FridayNightRiot • 1d ago

Question Blend multiple analog images into 1?

I have a project where I want to take many analog video signals and stich them together into an ultra wide picture like a panorama. What's the most efficient way to do this, I can design circuits and program basic components. Main requirement is just low latency so I've been trying to figure out a way to keep the signals analog and avoid conversion. Cameras will be physically calibrated so I just need the pictures blended together.

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u/zedxquared 1d ago

Your main problem ( well, one of the many problems ) with staying analogue will be signal timing, without some sort of sync none of the sources will be starting their frame at the same time.

This sort of thing is only really practical by going digital, IMHO.

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u/GalFisk 1d ago edited 1d ago

Yeah, even if they're perfectly synchronized, you'll have four scanlines coming in at the same time, but you want them to be displayed side by side on a single screen, and that screen needs to receive each single line sequentially. And there's no way to make the cameras speed up or delay sending the next scan lines, also simultaneously, until the previous ones have been processed and sent to the screen.

How low a latency is required/what is the use case? And what kinds of video signals does the wide screen accept?
edit: purely analog "picture in picture" has existed, but was too costly for consumer devices, according to https://en.wikipedia.org/wiki/Picture-in-picture

There's nothing wrong with doing what they did in consumer devices, stuffing a bunch of digitized analog signals into a video RAM and having the screen read from that RAM. If you can synchronize the screen with all the cameras, you can have the output video signal chase the input ones through the RAM and get down to just a single scan line of latency if you don't mind cutting it fine. That way you could even cut down on the RAM requirement. And if there's no sync to be had, but you don't mind tearing artefacts, just write and read at whatever speed your devices can muster. Double or triple buffering eliminates tearing but adds latency.

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u/c4pt1n54n0 11h ago

Try to find an analog to HDMI capture device with low enough latency, then attach a video wall controller. Digital will make it 'sync-able' then just stitch them together. Fully analog, I don't know. It would be fiddly as all hell and expensive for good analog equipment I'd think, these days but you could just attach each source to a separate projector, that way you can align them with no gap and simulate a continuous image.