hardware video feedback

[LEVLHED]

I just tried doing a feedback loop on my MX1, where I was running the RCA-out back into an input...wasn't that impressive...I also tried doing a more complex setup where I also ran the output thru my amiga/LIVE setup to a second input and was luma-fading between the two...better, but still not that great (http://www.levlhed.com/~levlhed/hardwareamigafdbk.mpg 63MB if yer interested)...
I was wondering if any of you had any tricks for producing good hardware feedback?
I'm very familiar with the camera-pointed-at-the-screen feedback, this isn't what I'm looking for...I want something thats not such a pain to setup and is more compact. I'm longing for hardware-based, real-time abstract imagery creation....

[KillingFrenzy]

So imagine that feedback is sort of like paint in a paint mixer. If you let it settle down, it just sort of goes grey. The trick is to have a way to inject some shape/color into the middle of that grey and get it whirling around. The whirling around is as simple as getting an offset on the original. This can be a simple vertical or horizontal offset, but usually a slight rotation gets things whirling properly.
Then, you need some way to inject some color/definition into the muddle. An Amiga is one way, but if that's the case I make the arguement that you might as well go for some updated software and a smaller piece of hardware. visualJockey can do some amazing feedback on live input, because you can route and control outputs and inputs. The slick thing is that you don't have to tap the bottom of the tier to get a feedback loop, you can grab an input from anywhere. I'll shut up about that, though, because I think you want something a little more "oldschool". My suggestion is to grab a cheap monitor (like one for an Amiga or C64), a camera, and a dedicated second mixer. Use your main mixer to feed your Projector. Now get a loop going within your second mixer with the camera and monitor. This way, your mixing on the feedback is seperate from your general mixing capabilites. Now, you should be able to get some feedback going by tilting the camera slightly to one side and aiming at the screen. This, in and off itself won't necessarily do much. You need to throw in a splotch of paint. One way to do this is with a physical object. This can be as simple as your hand, or as complicated as a laser pointer or light and mirror combination. Another was to get things going is to put a magnet near the screen. The latter method is not very good for the monitor, and might kill it, but that's what cheap monitors are for, eh? Now, by altering the angle of the camera, the adjustments on the monitor, and occasionally spicing things up with a hit of light or magnet, you should be able to get a good whorl of feedback going. I' ve found a Sony camera with "slow shutter" mode works well, or generally fooling with the exposure.
My best feedback experience was with a security camera hooked up to an Amiga genlock in a very dark room, and using a copy of Deluxe Paint to generate kaleidoscope patterns as a top layer. A perfect example of how with good software and heavy sleep deprivation you can basically simulate most heavy psychedelic drugs.

All that said:
I still think visualJockey is a great feedback tool, because you can get a live input, do feedback on it, and display the feedback without showing the original source as part of it. In other words, the output video can be pulled anywhere from within the feedback loop, and doesn't have to be a part of it. The result is, you can get a bunch of crazy feedback off of a spoon, or a radioactive, glowing pickle without seeing it sharply focused in the foreground and keyed on top, like a bad Iron Butterfly video.

[fluchtpunkt]

i once set up a feedback loop pretty much like the one described above: with two mixers & a camera recording either of the two previews - or the bigscreen. this setup was very nice because it gives you a lot of control over the feedback loop, but also over new signal input (which i could introduce with the mixers or by positioning objects between the camera & a screen).

Originally posted by LEVLHED
...I want something thats not such a pain to setup and is more compact. I'm longing for hardware-based, real-time abstract imagery creation....

currently i'm using a lot of feedback loops. ...virtual ones though: as killing frenzy already pointed out :) : with vjo you can model very interesting feedback loops (or entire 'networks' of/with feedback loops :cool: ) by simple click&drag. it's easy to setup or modify & very compact. also you have control over basically all properties of your signal & a big variety of filters at your disposal at any position in the loop/network (which calls for creative abuse :) ).
unfortunately it just isn't analog :( :) .

...

...I was wondering if any of you had any tricks for producing good hardware feedback?
...i find piece(s) of hardware that can control the following: hue, saturation, contrast, brightness; x-position, y-position, zoom in/out ...are useful in order to avoid 'assymetrical' behaviour (e.g. when you do feedback with a tv the signal usually 'greens' out - you can avoid this by correcting the hue of the signal somewhere in the loop).
then i personally find mirroring, inversion, distortion & chroma key effects the most interesting to use with feedback.

[LEVLHED]

oh, you darn VJohovas :) I don't have a lappy and refuse to lug my desktop PC to gigs anymore. Its nice to now that there is feedback mayhem in VJo, though.
And I know about camera-at-screen feedback (which if any of you newbies haven't tried yet, you're in for a treat).
I am looking for something more compact...like how I was running the output of my MX1 back to an input....fluchtpunkt, you got me wondering...what if I put some sort of video EQ between the output and the input? Something like the AV/FX kit that Dave sells? http://www.audiovisualizers.com/library/store/kitpage.htm
hmmm.....

It would be great if somebody made some kind of hardware specifically for creating feedback....but why would someone do that :)

thanks for the info so far!

[holly]

A zillion years ago people used to record audio on reel2reel tape. They'd make funky loops and delays by running the tape through one machine to record and across to another machine to playback a second later.... now of course it's done in-mixer.

Is there a way to do this with a video sampler box? Maybe like one of these (http://www.vjcentral.com/hardware/show/1676) and a color-adjust unit to fade it out after a few cycles? Maybe a custom two-head U-Matic thingie with looping cassette?

Probably easier with a laptop and live video-ins.... Computer lagtime would do it anyways, I guess.

[ToddGraft]

Yo Lev, was just gonna put that one up too, for all the confusion, we must be in sync too.
Frenz.....nice explanation of a few tricks there.

with analogoe keying you can tweak it to good effect aswell.
Creates a particle effect, good for smoking tornados if you get the right componemts together.
I was gonad post this up to see what the G man could explain about analogue feedback and its FX on thehardware on the MX50. I'll transfer to Repairs

[burstingfist]

Lev, could you provide a sample of the type of feedback you are looking for? I can do some interesting feedback things with my MX12, but I am not sure if it is what you are looking for. Here is an example of feedback produced with only the MX12 and a VCR:

http://12.224.176.25/video/WJMX12_Feedback_pt1.avi (28MB)
http://12.224.176.25/video/WJMX12_Feedback_pt2.avi (53MB)
http://12.224.176.25/video/WJMX12_Feedback_pt3.avi (54MB)
http://12.224.176.25/video/WJMX12_Feedback_pt4.avi (71MB)

This is a DHCP address, so the link may not work if my address changes. Just lemme know and I will edit this to reflect my current address. The first part is kinda lame, it took me a bit to get the feel of it...

[LEVLHED]

I put parts 2 & 4 DL to check it out, looks like they're gonna take a bit so I'm gonna hit the hay and check 'em out in the morn.
What kind of feeback am I looking for? I don't know really...just trying new (well, new to me) techniques and seeing what happens...haven't come up with anything that I like yet, so I'm asking all the vidiots here for some ideas!

Can you explain how you have yours setup to make this? where is the VCR put in the mix?

thanks for taking the time to make those examples!

[burstingfist]

Originally posted by LEVLHED
Can you explain how you have yours setup to make this? where is the VCR put in the mix?



Equipment list:
WJ-MX12 mixer
VCR1 (no tape, just loops Video1 out back to Video1 in)
VCR2 (Tape playing into Video2)


It is very simple, I have the mixer Video1 output to the input on VCR1. VCR1s output goes to the input on mixer Video1. Then I have VCR2 playing a tape on mixer Video2 (the sync channel of the MX12). Then I proceed to fuck with the effect knobs, fader, and wipe patterns. I feel like I only scratched the surface of feedback with this thing...



P.S. I should have mentioned in my first post that I used 2 VCRs. The reason I didn't is because 1 of the VCRs wasn't doing anything, it was just looping the signal back into the mixer. So I assumed that one could just plug the out of Video 1 into the in on Video 1 to get the same effect, but I guess the VCR adds a slight delay that cause the juicy feedback. I assume you could use some other video device with video thru to acheive the same effect.

[KillingFrenzy]

Hehe,

I once used an EOS, which is a high end, component standards conversion unit ($30,000 or something, if I remember right) to play with feedback. It essentially had all the functions of a tbc, but also could squeeze and reposition as well. The result was that I had a fair amount of ability to "steer" values with a very smooth spinning, high precision dial. I could warp color values, brightness values, or positioning to get feedback really going. I would also alternately zap in an external source to sort of snapshot and then play with. I wasted good hour and felt pretty stupid afterwards, because I should have been recording it. Ah, the old days and the advantages of working graveyard shift.

Lev, I thought you had a frickin Rebelle... shouldn't that be a good feedback distorter? If it isn't, then what the hell IS it good for?

Contentiously,
KF

[MoRpH]

Hehehe frenzy has a point.

BTW Fairlights are GREAT in a feedback loop :D

[LEVLHED]

Originally posted by KillingFrenzy
a frickin Rebelle... shouldn't that be a good feedback distorter?

It seems you've joined MoRpH in his little quest to try and bad-mouth the Rebelle at every possible chance? greeeaaat. So you don't like it/don't get it...move on.

The rebelle might make a fantastic feedback distorter, but its also PAL only and all my other kit is NTSC. I don't have a way to try it! (anyone interested in trading a NTSC MX1 for a PAL version?)

Burstingfist, I've watched a couple of the examples you posted. That is along the lines of my goal. I want to do sort of the same, but with out having to play a tape like that...ideally I want it to be completely abstract and produced in real-time w/out using any pre-recorded material. (and what the hell was that movie you used?)
Maybe what I have in mind isn't possible...or possible but not very interesting...

[MoRpH]

Originally posted by LEVLHED


It seems you've joined MoRpH in his little quest to try and bad-mouth the Rebelle at every possible chance? greeeaaat. So you don't like it/don't get it...move on.


:zzz: :zzz: get over it LEV, I think he was just wondering why your weren't using it with the feedback loop. Nothing about your little insecurity.

[burstingfist]

OK, took the playback VCR off of Video2. This just uses 1 VCR as part of the feedback loop, though you could use any device including your rebelle.

http://12.224.176.25/video/WJMX12_RawFeedback_thruVCR_pt1.avi (40MB)
http://12.224.176.25/video/WJMX12_RawFeedback_thruVCR_pt2.avi (28MB)
http://12.224.176.25/video/WJMX12_RawFeedback_thruVCR_pt3.avi (44MB)
http://12.224.176.25/video/WJMX12_RawFeedback_thruVCR_pt4.avi (38MB)
http://12.224.176.25/video/WJMX12_RawFeedback_thruVCR_pt5.avi (64MB)
http://12.224.176.25/video/WJMX12_RawFeedback_thruVCR_pt6.avi (37MB)
http://12.224.176.25/video/WJMX12_RawFeedback_thruVCR_pt7.avi (28MB)

-- Or the Full version--

http://12.224.176.25/video/WJMC12_RawFeedback_thruVCR_FULL.avi (281MB)

By the way Lev, that movie was "Flesh Gordon". A B-movie slightly better than Barbarella...

[syzygy]

For some of our gigs, we do feedback by using an MX1 and a WJ-AVE5 together.

There are lots of different ways to hook them up that give loads of different effects. Here are some of the things we have done:

* Patching the feedback input to two inputs on the MX1 and using the horizontal flip effect and a wipe to get feedback that goes left and right (you can then use a wipe on the AVE5 to control the left and right cutoffs of the feedback) Doing this to some clips of a posing bodybuilder gave him some extremely long limbs...

* Using the superimpose on the AVE5 based on the external camera in to single coloured shapes that are then replaced with feedback by chromakeying them to a feedback input on the MX1. The effect can be varied by using the horizontal and vertical flip effects on the MX1

* Using the superimpose effect on the AVE5 to introduce shapes into the feedback channel, 'seeding' it with new pixels.

* Using the lumakey transition on the MX1 to have feedback only in brighter parts of the image. The actual feedback itself can be manipulated with the AVE5

* Seeding the feedback with clips triggered from computer, using a reversed lumakey transition on the MX1.

There are loads more possibilities - two mixers gives you a lot more freedom and control over the feedback.


Something we've talked about doing is projecting onto smoke, and feeding a camera shot of the smoke back in as feedback. Has anyone tried this?

Dan.

(SyZyGy Visuals)

[LEVLHED]

yeah, burstingfist..thats more what I had envisioned was possible..cool...I gotta go see what I can do! I think having the VCR in the loop must make a big difference..it must introduce noise so the feedback has something to groove on....think I'll see what happens with just a hard switcher in there..
I assume your getting the pallate shifts by switching the background colors on the mixer?

And I can certainly see how using 2 mixers increases the possibilitys exponentially...

Also, while on my little jaunt this afternoon, I thought of a way to produce feedback within the rebelle. so I gotta investigate that too...hope I don't blow it up...

cool, glad I started this thread...keep 'em coming :)

[many2]

My last show was on 7 mixers and VJ Cinetik and myself would never have been able to put our setup to good use without some tricky wiring plan. Since all mixers were connected together in some way, much like in a vJo composition or a data flowchart, we were able to make almost infinite variations just playing with wipes (not that we limited ourselves to wipes !!!). What was really interesting was that we were projecting on 6 screens, so each screen was a variation and people had a lot to watch. I never had so much fun mixing visuals before ! With our mixing monster we were able to change the image on all screens in a different manner playing with just one or two different controllers at a time. Don't be afraid to try it yourself : meet with VJ friends and connect your mixers together, or rent some more. It's easy to get messy with feedback loops, but it's possible to keep it clean at all time with some experience.

Many-2

[syzygy]

Wow Many2 - that sounds like my dream come true!

We've just got ourselves a 4 input, 24 output distribution amp that we are planning to put to good use with multiple projectors and CRTs.

Now we need some more mixers :) Unfortunately we've blown our gig takings for the next month on a new Laptop so new kit is going to have to wait a while...

Dan.

(SyZyGy visuals)

[LEVLHED]

enough OT! I'm only interested in developing system video feedback at the moment...

I tried running the feedback loop through a clunk-box...it didn't do the trick. Tried it with a VCR, and it was similar to the examples that BurstingFist posted (but with the flow running from right to left). I just did a 5 hour render with those results, doing a quad mirror kind of thing to make it symmetrical and changing the color pallate every minute or so...oh and sped it up 300%..made a 20 minute VCD (which will make the "AVIT cut" :)
The idea I had with the feedback on the Rebelle didn't really work..I need a way to put video signal into the loop, since it doesn't really produce any on its own (I assume this is why it didn't work in the hard-switcher example)There are two video outs on the rebelle..a "main" and a "preview"..all I tried was running the preview output back to the input...nothing much happened :(

Does anyone have ideas on how one could produce an effect like the mixer/VCR loops, but without a mixer or VCR?
Could using something like a video amp, hard switcher, and Y cables produce anything? I don't have any video amps, or I'd try...
Does anyone understand what I'm trying to accomplish? realtime/abstract/analog-ish/COMPACT

[ToddGraft]

Don't be afraid to try it yourself

Hi was gonna post a while back on this thread, about this.

I had a MX50 malfunction with my luma and horizontal sync.
On its most acute adjustment, it was obvious that there a horizontal shift in the signal. I wasn't that concerned untill, periodically i would get a loss of chroma signal completley resulting in B/W on the B channel.
All leads checked and after several sporadic happenings I decided to get a service check. The first thing the repairers asked me after finding out my use for it , was, "You have not been putting feedback through this, seems to be the biggest percentage of repair we have to do these days, Its not like the old days when you had professional ppl who knew how to look after their Equipment."
I pointed out that most 'professional' ppl have never owned a bit of kit in their lives:)
and that ppl use these tools for artistic reasons, aswell.
After a large quote, decided that I would only use feedback in emergencies or the odd Trance gig.

Maybe it was just a rumour but it would be nice to get a sparks knowledge on that.
btw not had problems since I watched my level of intake........... vs outake. lol:)

post a pic on forum

[LEVLHED]

I was wondering if feedback like that could harm the guts...does anyone know more about this sort of thing? I would hate to fry out my shit....I can't afford to buy all the new things I want, much less worry about paying for repairs/replacement....

[ToddGraft]

Hey, Mr Rebelle, as I was posting the last pic, I thought that you where probably going to dicuss that in the workshops at AVIT and you where generating some interest in the subject.

Am I right in understanding that the horizontal sync will be overloaded and burn out can be expected.
Seems like most manufacturers spend a lot of time and expense to stop this occuring, whilst we as pioneers in digital art can turn all this negative feedback into a positve thang.
****************FORUM USERS***********************
If you can't make it to AVIT this weekend we would still like your support. We will be hosting the next AVIT as soon as we can. Untill then please feel free to DONATE to the cause, we still need your financial support to meet the cost of production. thanks in advance.:D

Another pic to brighton these pages with our work

[brain]

yes anyone who ran into hardware trouble because of feedback please report your painful experience...

until now i did not have any trouble while feedbackin' with an mx-1 and mx-12 and several other tech inbetween, but i don't want to find out the hard way :rolleyes:

thx brain

[sleepytom]

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=1386825512
video delay lines on ebay

[LEVLHED]

very interesting, G...so you're suggesting a video delay unit put in a i/p-o/p feedback loop will provide interesting results? and doing this should also cap the signal level to respectable levels to avoid overload?

sleepytom, that video delay rack is listed on the U.S. ebay website too...looks like this is the third time he's listed it at that price w/ NO bids...think I'd wait for him to lower it on the next auction :)

otherwise, something like the attached pic certainly LOOKS like what I'm looking for (if it does the job)

are there PAL/NTSC issues I should be concerned with on video delay units?

[skyvat]

I've been trying to get satisfying MX-1 feedback results as well. One trick someone showed me is to use input fx on the feedback channel, turning on the second and third values (negative and something else), and flipping the image either hortizonally or verticaly (or both). It tends to work best with high contrast images, so you can lumakey through the lightest parts easily. With the right material, it results in some really chunky looking patterns - maybe not beautiful per se but interesting. Give it a shot if you haven't already. I don't know if you can burn up a digital mixer this way - but I know a few people that do it frequently and their gear seems to withstand it. Anyone out there toasted Videonics units with this type of method?

Now my question. If you add a second MX-1 to the line, where does that get you? Any setup advice for linking two of these mixers in tandem? I'm practicing with a fellow vj next week and want to combine gear.

Thanks -
Dan

[rockthomas]

Has anyone a more definitve answer on the feedback damage issue. I have only used a very old studio board that used tubes, I believe, which seemed safe at the time. But, I need to know about more compact mixers.

[DrEskaton]

Anyone got any tricks or tips for hardware feedback specifically on the V-4?

Seems that with the "input delay" setting in the menu you should be able to get some good results, I've been meaning to look at this for some time but haven't had a chance yet?

Unfortunately I can't find any functions that do a rotation on the image which is what you'd really like for some good feedback????

[LEVLHED]

I don't own a V4 or I'd have tried this already...very interested to know what happens though!

[rockthomas]

I basically connected a whole studio setup together into a big loop. A studio camera provided the inital 'oscillator' and I used normal wipes as an 'LFO' that actually got things moving. From there, everything degenerated into liquid colors. No real delay was used and everything worked fine. However, I believe this system used tubes. In this setup, the effects processor seemed to buffer the signal. It seems reasonable that a input-mixer-fx feedback loop would be adequate to protect gear or insert a small strobe in the line to break things up. Any more information on specific problems related to feedback would be very interesting.

[sleepytom]

the main problem with feedback (both from a technical damage and artistic view point) is the way the signal is rapidly amplifyed - this is why it tends to go to white and to damage equipment.

putting a video limmiter o even a simple fade to black box in the loop will stop this from happening and give you better control over colours.

adding a delay line (or something like a vcr that has a small input>output delay) will give more space between the trails

tivo or other time shift vcr could probably give intresting results.

colour correction gives nice contol over the colours (doh)

[holly]

In a thread about the Korg Kaos Entrancer (http://www.vjforums.com/showthread.php?threadid=3491) Kriel lists many video effects including some which might rotate the screen (at least by incriments of 90 degrees, but more will be revealed when this device hits the market). Could trick this puppy in your V-4 loop and Bob's your Uncle.

[sleepytom]

a mixer with zoom (such as the JVC km2000) will add a really nice effect as will horizontal or vertical flip.

[videobox]

I use 2 MX1s at a minimum. The second one is just an EFX box, that is, I assign the 4 channels to the one input and set up them up as 1-uneffected input, 2-negative image 3-mirror image 4-mirror image with negative. Sometimes effects are applied to the first mixer as well. Often I use a horizontal squeeze transition on one and the vertical squeeze transiton on the second. A camera and monitor is used to complete the loop. Usually Video Toasters and Videonics VE-1s are in the loop as well. I'll need to digitize some footage and post it for Ya'll. Some still images of my very early stuff, with video feedback as being a part, can be seen here:

http://users3.ev1.net/~forbus/rave_image.html

:alien:

[vjvishnu]

Orrigionally posted by HoLLy
A zillion years ago people used to record audio on reel2reel tape. They'd make funky loops and delays by running the tape through one machine to record and across to another machine to playback a second later....
Is this (http://members.fortunecity.com/siys/videoart.html) what you mean HoL? (esp. check the diagrams)

This dude, StEvO, seems to have had this and other kinds of feedback sorted since the early 80's.

The medium is still young.

[videobox]

The sTeVo iN yR sTuDiO was cool. I have heard of using the long tape delay method for audio decades ago. But that is the first time I have ever heard of it being used for video. I don't think the long time delays are the best way to go. They certainly have limited usefulness in audio applications. (I used reel-to-reel tape delay 24 years ago, myself.) There are certain applications for long delays in visuals, but I think it's worthless for video feedback.