CMP-DIV Video Effecter

RingMad · Posted: Fri Jun 22, 2012 3:40 am Post subject: CMP-DIV Video Effecter

This post was originally stuff from another thread, and now that there's this subforum, it was thought better to put it in its own thread.

I made a video effects box which perhaps only slightly qualifies as doing synthesis, and it deals with sync in a rather simple manner. No sync generator.

Basically, it splits a composite video signal, slices it up using an LM339 comparator which clocks a 4040 divider (that's where the CMP - DIV of the title comes from), then adds a few of the divisions back to the original signal. Since the original signal is still there, the sync is preserved. Limited, but some fun stuff for such a dumb circuit.

It's also known as the Vidiffektor: http://www.jamesschidlowsky.ca/electronics.html#vidiffektor . There be a link to a demo video that shows pretty much what it does.

My friend who actually came up with the circuit had originally conceived it for audio, but then we wondered what it might do with video. We each took it in slightly different directions, but the core idea remains.

Warning: Use at your own risk. I cannot guarantee that this won't break equipment this is connected to. In certain cases, this can add a DC offset to the output signal, so it ends up between 1V and 2V. It is beyond my electronics knowledge to know if this is bad or not.

James.

P.S. I used this circuit to produce my avatar-self-portrait... those wavy lines are classic CMP-DIV effects.

Edit: Changed my website URL.

CMP-DIV Video Effecter schematic.jpg

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jjplano · Posted: Tue Jul 31, 2012 1:26 pm Post subject:

hi RingMad

thank you so much for sharing this

I was looking for some video projects, because audio isn't really my thing

but my knowledge is very limited so far, so it's not easy, video is harder Sad

question: do you think this would work on PAL?

thanks again

RingMad · Posted: Wed Aug 01, 2012 4:30 am Post subject:

jjplano · Posted: Thu Aug 02, 2012 4:46 pm Post subject:

hi James

well, I got the components I didn't have and I build it and... it doesn't work Sad

I don't know, as I said, I don't have much practice in all this, but this is a pretty easy circuit, so I checked eveything three times and everything seems to be in order

do you know if someone has build it based on you schematics?

perhapps I can send you a couple of pictures of my bredboard

I was really looking forward to this, I have never build any circuits for video processing

thanks

edit:

this is my breadboard, look

vidiffektor-breadboard.jpg

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RingMad · Posted: Fri Aug 03, 2012 3:17 am Post subject:

jjplano · Posted: Fri Aug 03, 2012 8:29 am Post subject:

I have image, and with the "raw" pot I can kill it

"threshold" pots doesn't do nothing at all

the pots coming out from the 4040 does affect a little the output signal (when the "raw" allows it to pass through), but there is close to no change, and it seems to be more like a "threshold" o desaturation kind of effect rather than another thing. no wavy lines here

perhapps I connected things the wrong way

thanks

Javier

RingMad · Posted: Fri Aug 03, 2012 12:53 pm Post subject:

OK, I checked against your breadboard image and it looks like you connected the circuit correctly.

Now, when testing, keep the raw level at max, i.e. 0 ohms, so as to not choke the sync. If you choke it too much, then the image will loose sync. (It's just that I found one can get interesting effects by playing with this (very gently), once one has found the right threshold level).

I guess I should have explained better about the threshold, because it's the most important and difficult part. To start, leave the 1K fine tuning in the middle of its range. Now, slowly sweep the coarse threshold pot, watching your screen carefully. You might easily pass by the right spot. It might just be a quick flicker on your screen. If you see something like that, make very small movements back and forth near to where it flickered and try to find the sweet spot, then use the fine tuning pot to better pinpoint it.

I looked at the signal diagrams for PAL and it's quite similar to NTSC in its overall range, but perhaps with a small offset. I don't really know how that all works, but perhaps for PAL, a larger pot is needed in order to find the sweet spot. Try 100K instead of 50K... but turn it even slower, because the higher the value of the pot, the less precision there is.

Also note that different input signals may have different threshold settings. e.g. from a VCR or a camera, or a DVD player. One always has to adjust it to find the good level.

I'm sorry it didn't work right away for you... right now you are the PAL pioneer... exploring where no-one has!

James.

jjplano · Posted: Sun Aug 05, 2012 2:57 pm Post subject:

ok, I finally got time to test this the proper amount of time (and with the proper equipment)

and it works Smile

you should have put instructions since the beginning hahaha

couple of things were a little loose on the breadboard

the first 5K pot doesn't do anything here, so I'm gonna try put it in another Q of the 4040

thank you so much James, hope you try to come up with another simple but cool project like this one

all the best

jjplano · Posted: Sun Aug 05, 2012 5:28 pm Post subject:

I just wanna ask you something

it's possible that you can replace the 5k pots coming out of the 4040 for 1k or even less value?

I note image distortion/change in the really lower end of the turn, really close to 0 ohms

you too?

thanks again

RingMad · Posted: Mon Aug 06, 2012 6:01 am Post subject:

Glad you got it working, Javier! So it is confirmed that this circuit does indeed work for PAL as well as NTSC. Good to know.

JingleJoe · Posted: Fri Aug 10, 2012 1:23 pm Post subject:

jjplano · Posted: Fri Aug 10, 2012 4:56 pm Post subject:

hi JingleJoe

I still have the original design by RingMad on a breadboard

so, if you want, point out your modifications, because it's easy for my to test them out, no problem

RingMad · Posted: Sat Aug 11, 2012 3:41 am Post subject:

JJ: I've already built 2 boxes with this circuit, but sure, I wouldn't mind hearing your mod ideas... admittedly, it's a pretty rough circuit. Heck, I think one is supposed to ground the unused comparators or something too.

My friend who came up with this circuit used a summing amp at the end, but I had observed it made no difference, so I didn't bother.

James

JingleJoe · Posted: Sat Aug 11, 2012 6:51 am Post subject:

This will definately need testing; if you would be so kind Mr jjplano, that would be helpful, but no dire rush or anything Smile

This new arrangement should allow greater functionality and stop the controls interfering with each other.

I would advise a non-inverting amplifier at the end with a gain of about 4 (I think) to bring things back up to the level they were originally. However that will need testing/experimenting with, I don't know what kind of voltage the video input is expecting.

VIDEO EFFECTER UNTESTED MODIFICATIONS.png

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RingMad · Posted: Sun Aug 12, 2012 4:47 pm Post subject:

Thanks for the mods/advice JingleJoe... if I have a moment sometime to try them out, I will.

jjplano · Posted: Fri Aug 17, 2012 8:01 pm Post subject:

sorry for the delay on my answer, I was swamped with stuff

JingleJoe, I have the new circuit with your modifications, and I have no image at all

if you want to try something different, please let me know

but please do it the following couple of days, 'couse I want to turn this into a device the next week

cheers

brock · Joined: May 26, 2011 Posts: 112 Location: Canada

jj,

I've tried to figure out what the original circuit actually does and my best guess is it works as a phase lag circuit by messing with the output impedance, and it can also impose a small level shift depending on the pot configuration on the 4040 and the 339 output level.

Joe's modified circuit cannot work as the video signal source impedance is 100k driving a load of 75 ohms, so the video out will be 750 uV at most. The variable 1k max pot in the original circuit is a huge series resistance for a video signal to see and I'd guess the circuit works best with it set to 250 ohms or less. RingMad mentioned the comparator threshold setting is critical and I'd agree (without having built the thing of course). The threshold must be set in the video signal and probably above the colour burst level where it could screw up the black level clamping which, depending on your tv, could result in no output.

Good luck with this, Brock

jjplano · Posted: Sun Aug 19, 2012 1:11 pm Post subject:

hi brock

I was just thinking that the no image has something to do with the high values of the resistances JingleJoe added

so I'm going back to the original circuit

as I said, very little electronic knowledge on my part, sadly

thanks

brock · Joined: May 26, 2011 Posts: 112 Location: Canada

JingleJoe · Posted: Mon Sep 03, 2012 4:23 am Post subject:

jjplano · Posted: Mon Sep 03, 2012 8:33 am Post subject:

those are tips for the next guy who tries it Wink

finished project

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RingMad · Posted: Mon Sep 03, 2012 2:02 pm Post subject:

Nice work Javier! Thanks for reporting your success in building it. Have fun!

James.

neoxide · Posted: Mon May 26, 2014 4:36 pm Post subject:

Just thought I'd post my build of James' CMP-DIV circuit. Here I've included the circuit in a box with two 'dirty video mixers' (just one at the moment) to give a processor that can be used for blending video sources together on the fly, as well as adding some colour distortion and distinctive CMP-DIV effects.

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I also made a few videos with it.

https://www.youtube.com/watch?v=_F7T6tF_Y-8
https://www.youtube.com/watch?v=Ge9-eTLtdWc

RingMad · Posted: Tue May 27, 2014 2:40 am Post subject:

Thanks for posting that, neoxide! Nice to see that the circuit is getting around. And throwing in those video mixers is a cool idea.

James.

jondent · Joined: Oct 04, 2013 Posts: 8 Location: Australia

looks like a fun build.
I'll definitely give this a go