CMOS video synthesis

[Top Top]

Hey guys, thought you would appreciate some experiments I have been doing with video synthesis. At the moment, I am laying video on top of an existing signal, and using that signal to generate the sync to format my signals (I am just using the blank blue screen from a VCR in these videos, but this could go over a camera input, etc, as well. Eventually I will be using the blackburst out on my video mixer to generate the sync signal and have a "blank canvas" to generate images on)...

This uses the following chips:

LM1881 Video Sync Extractor - takes an incoming video signal and generates sync information from it.

4093 - Two oscillators: one tuned for horizontal line generation, one tuned for vertical line generation (basically tuned a lot higher so that the oscillator sweeps several times within each horizontal scan line).

4017 - Divides the vertical line oscillator to create variations in vertical patterns.

4069 - used to invert sync pulses from the LM1881 to trigger the necessary blanking periods.

4016 - Triggered to ground the oscillator outputs during the sync periods (to keep the image stable from a composite output).

40106 - used in a circuit similar to Tim Escobedo's "PWM" circuit (modified to cater to video signals) to alter the pulsewidth of the vertical and horizontal oscillators.




These videos were shot on my crappy phone camera, but you get the idea.

This is all still on the breadboard. Some other ideas I'd like to try:

4031 - in looper configuration to capture/loop some patterns.

4017 set up with a fader on each output, and a very high speed clock, to generate waveform tables for onscreen patterns or for animated pulsewave modulation of the other two oscillators.

[commathe]

Awesome!

Do you have schematics? I'm quite interested in this kind of stuff too.

[Top Top]

Thanks, no I don't really have any schematics at the moment as I am still in the experimental phase, and am not 100% sure of what I am doing, or why some of the images look the way they do, still learning about video signals as I go.

Are you familiar with the way video signals are formatted, with the scan lines and the sync signals that are included off the edges of the screen?

Here's one more video from tonight. It shows the PWM control, which I am adjusting by hand to change the width of the vertical lines. I am pretty sure the blinking diagonal squares are from the divider in the circuit.

[billsship]

Very cool! I wonder if this could be adapted to fit in existing lunetta systems to turn them into both an audio and video unit.

[Top Top]

One definitely could interface both and have both going on at once, and could build a lunetta video system that is very similar in operation to audio lunettas. Video is a little more picky about what will generate a pleasing image, as many things will just look like snow or diagonal scrambled lines.

[droffset]

Great results, I started playing with this a while back but didn't get far.

[RingMad]

Great stuff! I never got too far with my experiments.

So I guess I should find myself an LM1881.

Thanks for sharing,
James.

[Top Top]

James, I was thinking of your stuff when I started working on this. It's not too far out from what you have been doing, just with a sync chip to help stabilize the images that do not come off the video signal input.

I tried some experiments with just running video through a divider as well, and got some interesting results.

[Top Top]

And here it is in the middle of an electronic feedback loop with my video mixer.

[inlifeindeath]

love it Top Top! keep us updated on your shenanigans!

[Ruebezahl]

Wow this is really cool!