Composite Analog Video Wall (aka how did that work?)

Thread Starter

zumdar

Joined Feb 2, 2014
5
I was looking through this old thread about composite video cropping in the interest of creating my own analog 'video wall' type setup.

I want to take in a single video signal and split it out to say 9 tvs. I was imagining splitting the signal and sending it to 9 modules that crop and zoom the incoming signal so only a section of the video plays on each tv. I know this can be done with a raspberry pi video wall setup, but I am more interested in an analog way, more of a learning project then anything super practical. Does anyone have any insight into how the old analog video wall systems worked on a circuit level? its been hard to find much electronics information on the old systems..
 

ronsimpson

Joined Oct 7, 2019
1,025
I don't think there is a analog way.
Maybe if all 9 cameras were synchronized, so each is at the exact same spot in the picture. But cameras do not come synchronized. Each will be at a different place in the picture. This forces us to store one picture for each camera in memory.
 

Thread Starter

zumdar

Joined Feb 2, 2014
5
what do you mean synchronizing the cameras? I am trying to take one video signal in, split it to 9 different tvs all displaying a different section of the video. essentially 'cropping' the main video into a lot of smaller segments. there would be only 1 camera sending signal to a bunch of different tvs.

these analog video walls were a thing that was around in the 90s i believe but I can't really figure out how they did it. the equipment seems to be pretty esoteric and hard to find.
 

crutschow

Joined Mar 14, 2008
25,686
the equipment seems to be pretty esoteric and hard to find.
Do you want each smaller section of the picture to be enlarged to the whole screen on each of the 9 cameras?
That would be rather difficult.

If you just want the cropped picture to be displayed in it's original location in each display, that would be much easier.
 

ronsimpson

Joined Oct 7, 2019
1,025
Analog way:
In the back room you have one monitor that displays the image that needs split up and put onto 9 monitors. Put 9 cameras looking at the one monitor. Position each camera so it sees only 1/9 of the image. Now connect the 9 monitors.
 

crutschow

Joined Mar 14, 2008
25,686
The problem is, you need to take an analog horizontal video line that occupies a fraction of a line and stretch it into one complete line.
That can't be readily done using only analog techniques.
 

Thread Starter

zumdar

Joined Feb 2, 2014
5
haha yess that would be a great way to do it real cheap and diy way!

There is no all analog way to do it. Here is how it was done in 1999.
https://patents.google.com/patent/JP2001100718A/en
this is great! i looked around for a while trying to find the full thing to see the figures but no dice.

I really just dont get it though, there are devices like picture in picture that zoom in and zoom out on a video signal, so why couldnt i use like 9 of those? i guess im realizing something like that must be digital zooms huh?
 
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