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multiple VCRs makes things go wacky?
MUFF WIGGLER Forum Index -> Video Synthesis  
Author multiple VCRs makes things go wacky?
giorgio
we've noticed that when hooking up multiple VCRs together in a video chain, whether through a cheap switcher or even into my panasonic mx-10 video mixer, things get weird. like even when only 1 VCR is actually sending signal, hooking up another into another input of a sima thing that has multiple inputs (only 1 can be selected at a time) it makes it glitch out. same goes for the MX-10, when hooking up 2 VCRs, the keyer input (which I run through a TBC, and works fine with iphones as the video source) gets "wobbly", like it shakes back and forth. sometimes the effects are cool and sometimes annoying. anyone know what this kinda of behavior is?

I'm trying to get ready to a triple star wars viewing party where we watch all 3 star wars through a video rig (not sure what the rig will be yet but 1 or 2 mixer/keyers and maybe some video effects processors) and when we use the 3 VHS tapes it doesn't work properly, but works fine when I play the videos from 3 iPhones. usually I'd just use the iPhones but I figured someone here might know what is happening.

thanks
lizlarsen
Tape-based media needs more stable timebase correction than a digital source like a DVD or an iPhone. Going into a video mixer should be fine, though, so if you're seeing some wobbliness there I would expect quality issues with the video mixer rather than the VCR itself. The LZX definitely doesn't like to sync directly to a tabe-based source that hasn't been timebase corrected first.
giorgio
hmmm maybe cause I'm only sending 2 of the 3 through TBCs, the 3rd one is causing the wackiness. When I tried 2 VCRs only 1 of them was going through a TBC, I will try 2 and both through TBCs and see what happens.
johnnywoods
also, a lot of this depends on the VCRs you are using. Most consumer level VCRs were not designed with mixing in mind. If you get high-end VHS decks (which go for a song on eBay these days), they should work better.
nickciontea
could someone elaborate on the different kinds of vcr's / tape decks?

i feel lost.. and not confident to shop.

vcr
high end vhs deck
Svhs..

and any others?
lizlarsen
Well one notable difference between a high end studio VHS deck and a consumer grade one is that the studio ones often have integrated Timebase Correctors, which makes a big difference.
giorgio
I bought 2 production vcrs with genlock and all that but Apparently UPS destroyed them before they even got to me and all I saw was a refund. I'm gonna stick with the iPhones for now and maybe get a decent VCR at some point just for effect/fun/simplicity
DonaldCrunk
if we're talking VCRs i'd like some input as well. i've got a literal mountain of VHS, several bare-bones consumer level VCRs and one dual-well VCR (also consumer level i fear) that i'm using for playback.

i'd like at least one nicer broadcast-level VCR, and i also need a (i assume Panasonic) VCR with an input for my 'tube type' panasonic camera that i rescued. the video synth wiki is helping me out with that one.

are there any 'standard issue' broadcast VCRs that would be widely available and easy to source parts for/add new units? i see the Sony EVO series a lot, but they're typically running at minimum 100-150 bucks on ebay. just wondering if there is something less expensive in the broadcast vcr world.
barto
have you guys tried running your vcrs into a mixer first? some mixers have TBC's built it so youll be able to mix two out of sync sources. from there you could plug into the LZX
nickciontea
i got the mixer with TBC.. just looking for good recommendations.

more tbc's cant hurt
giorgio
i'd love to find some small/cheap TBC/fram synchronizer but so far everything is a deep rackmount thing or some other mad clunky thing. This seems like such simple technology. maybe an arduino can do this kinda work?

also there are tons of cheap pro VCRs on ebay for like $20-$30, old panasonic ones is what i feel like I have seen (and tried to purchase)
lizlarsen
Despite how simple it seems like it should be, a genlockable frame synchronizer is actually a really complex device. Our implementation with the CVD&FS is FPGA-based and is a 4-layer, dual-sided board packed with parts and pricey chips. Arduino can't come even close to the frequency required to sample video. Ours won't be cheap, but it'll definitely be small compared to the rack-mount devices (12HP module.)
giorgio
yeah i figured speed might be a factor with the arduino. oh well...
lizlarsen
An arduino or AVR with a genlock'ed clock running the microController could do all sorts of fun CV and frame-rate related things though.
daverj
While an Arduino is fast enough to control the video circuitry in a TBC, it's maybe 1,000 times too slow to be able to actually process the video data itself. That has to be done with more complex (expensive) circuitry.

My video synth system will also have a couple of models of TBC coming out this summer.

You might also keep your eyes out for a dual TBC board on ebay. There were a couple of companies that made them. One was called the Kitchen Sync and was an ISA bus board for the Amiga or PC, but only used the bus for power. But to control it's settings you either need to have an Amiga and it's software, or the optional hardware control box. We had one in the studio at the Experimental TV Center for a long time.

http://www.amiga-hardware.com/showhardware.cgi?HARDID=1298
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