Vision mixer or switcher?

[travis1234]

Hey all,

 

Just a quickie, doing a gig at end of the month and im a bit new to the video side (im an LX) but anyway, I have a simple setup, a projector with a camera but I want to be able to fade the cam out, so is a vision mixer or a basic switcher the way to go?

 

Oh and is it a bad idea to try and run video through XLR? This would be really useful as ive just installed a new multicore and from the control room to the stage its a long way (multi-purpose venue)

 

Thanks in advance.

 

Travis

 

Forgot to mention. Cam is composite!

 

Trav

[Bobbsy]

1. Unless we're having a little problem with terminology here, if you wish to fade the camera you'll need a vision mixer. A switcher would simply cut the camera away without the fade.

 

2. It's bad practice to try and feed video via audio cable. Cable losses at video frequencies will be extreme, especially over any sort of distance. That said, there are line driving amps that include pre-emphasis to compensate for the HF losses over audio and/or CAT 5 cables and one of these might work in your situation. However, my choice would be to run in a dedicated piece of co-ax.

 

Bob

[travis1234]

Cheers Bob,

 

Only brought up a switcher because I have used a teeny little one in the past that had faders and composite in & outs.

 

Ill question further tomorrow.

 

Travis

[Tomo]

If you're only using one camera, some of them have some built-in effects.

These usually include a 'fade-to-black'.

 

Would be a lot cheaper than hiring a vision mixer.

[Bobbsy]

Only brought up a switcher because I have used a teeny little one in the past that had faders and composite in & outs.

I wondered if we had a problem with terminology...

 

...if it had faders, I'd probably call it a vision mixer. A simple one, yes, but it can clearly do more than just switch.

 

Bob

[James]

Sorry Bob but there is nothing wrong with Travis' terminology.

 

Some companies, GVG included have been known to call what you or I would nowadays call vision mixers, Video Switchers.

 

http://cgi.ebay.com/Grass-Valley-GVG-Switc...9QQcmdZViewItem

 

It's odd but technicaly valid terminology.

 

James

 

(We just chucked the last of 9 GVG200s - still have the odd GVG110 in service though)

[Bobbsy]

Hmmm...not so odd I guess. The term in North America has always been "Switcher" for a box that we would call "vision mixer" The same applies to the person driving the box BTW. I guess GVG ran out of money to "brand" their equipment for the non-American market.

 

Certainly, more normally in the UK, a switcher box that lets you switch sources but not add any effects. This can be anything from a simple row of mechanical buttons not even doing a synchronous switch, to a full-blown routing matrix. A vision mixer, on the other hand, is the sort of thing used in a control room or edit suite for production purposes..and containing some form of effects, ranging from simple mixes and wipes up to full digital magic.

 

Where it gets confusing is when somebody asks if he needs a "switcher" or "vision mixer" if we're now to take the two names as synonymous! In the OP's context I had to take him as meaning the more "British" definitions, otherwise the question was meaningless.

 

Bob

[paulears]

I think it's just yet another US term leeching into general UK usage - I notice few of the broadcast manufacturers have any vision mixers in their product range any more - but offer switchers. Personally 'mix' makes a much better descriptor than a 'switcher' (that can mix) Daft innit!

[GRisdale]

Oh and is it a bad idea to try and run video through XLR? This would be really useful as ive just installed a new multicore and from the control room to the stage its a long way (multi-purpose venue)

 

 

Canford sell some adapters that have 75ohm bnc in and XLR out (both ways). Would give you a link but I'm not at work with my catalogue and the website is as ever a mystery...

 

Someone with slightly more video engineering knowledge will no doubt correct me, but as I understand it these will convert the signal impendance to allow the video signal to travel down your mic lines unaffected and then convert back at the other end. Someone I know has used them successfully, though I don't know the length of cable run...

 

"Video switcher" is indeed the American name for a vision mixer and is quite an annoying and confusing term in the world. I generally assume that someone asking for a "switcher" wants a "mixer".

 

Something like a Edirol V1: http://www.dv247.com/invt/21985/ would be fine for your purposes.

 

...impendance to allow ...

 

IMPEDANCE!

 

:o

[Tomo]

In a word - it's not a good idea to send video through XLR.

 

XLR simply doesn't have the bandwidth.

 

What will happen is that it will work for short runs, and go black&white and fuzzy over longer runs.

[J Pearce]

Ive run about 100m on XLR, it was still colour and was fine for a backstage monitor.

However the quality was significantly affected, enough to make it too poor for FOH stuff.

 

On a tv backstage fine, on a projector or large screen or recorder dont do it.

[dbuckley]

Some companies, GVG included have been known to call what you or I would nowadays call vision mixers, Video Switchers.

And theres the rub - "nowadays". A production switcher has always been a switcher, since the beginning of time. A vision mixer was the (I would say young lady, but no matter how true as a generalisation it is, its still sexist) person who operated the switcher.

 

Update: Just found this picture from a page called switching and video effects

 

http://www.danalee.ca/ttt/images/11/SWRFULL.jpg

 

 

Then we started getting into accessible stuff, and somewhere along the line the term "mixer" was applied to differenciate something cheap that (by the traditional term) switched video (ie could do a wipe), from something even cheaper that really did just select video with a switch.

 

(We just chucked the last of 9 GVG200s - still have the odd GVG110 in service though)

You did what? I do hope not, I hope they went to appreciative homes. A Grass 200 may altogether less portable than a Panny or something, but will continue to do what it does for another few decades if looked after reasonably.

 

In a word - it's not a good idea to send video through XLR.

You're absolutely right, of course, neither should we send intercoms, DMX, mouse buttons, but we do, and it (almost) always works :o

[Bobbsy]

Yeah, dbuckley...but that was a CANADIAN web site. Canada (and I know this cause I'm a Canuck myself) has always called them "switchers" just like the USA.

 

Here in the UK, for as long as I can remember which takes me back to 1976, the production tool you pictured has always been called a "Vision Mixer". Indeed, both the electronics and the person pushing the buttons were both called vision mixers, just as they were both called switchers in North America.

 

As for the GVG200s, I know to my cost that it's hard to find such things good homes. The biggest sticking points is the need to provide all synchronous sources. The modern "prosumer" switcher/vision mixer has a basic synchroniser on each input and can accept free running sources. You need a better class of source to use things like the 200.

 

Bob

[dbuckley]

Yeah, dbuckley...but that was a CANADIAN web site.

I added the link and picture afterwards, I found it through a google image search to support my assertion that vision mixers were generally female :)

 

When I got taught basics of TV production in art school day release in about 1973 they were switchers then.

 

As for the GVG200s, I know to my cost that it's hard to find such things good homes. The biggest sticking points is the need to provide all synchronous sources. The modern "prosumer" switcher/vision mixer has a basic synchroniser on each input and can accept free running sources. You need a better class of source to use things like the 200.

Indeedy.

 

But I believe that some / most? / all? of the modern prosumer "things" :) have a TBC on each bus, not on each input, so you cant switch between sources on a single bus. Well you can, but the picture freezes or blanks as the TBC resyncs. You have to do the non-intuitive technique familiar to everyone who ever used a Grass, switching through preview, so transitions are always bus swaps.

[gnomatron]

But I believe that some / most? / all? of the modern prosumer "things" <_< have a TBC on each bus, not on each input, so you cant switch between sources on a single bus. Well you can, but the picture freezes or blanks as the TBC resyncs. You have to do the non-intuitive technique familiar to everyone who ever used a Grass, switching through preview, so transitions are always bus swaps.

 

The odd thing, is that this is a perfectly intuitive technique to anyone who's tried to use a 2-channel dj mixer with more than 2 sources... my VJ setup has become ridiculous, with 4 inputs to bus on my mixer and the laptop going to the other - the really ridiculous bit, though, is using the laptop as a preview monitor for the other bus, via a capture card. Gives nice flexibility, though.