tv wall and home made video matrix

[AberNStein]

i'm doing tech for a school production of macbeth, and the director wants a 'tv wall' as well as two projected screens on stage.
i've pretty much figured out what i want to do, but i found this forum and thought i may as well post my plan and see if anyone has any suggestions.

so, to get one image split up into ten pieces for the pyramid of tvs she wants, i'm going really lo-fi, and am going to point cameras at different parts of one tv. we're using little security cameras, which won't turn off when idle, and will be easy to attach to some sort of frame. we're gonna use rg6 coaxial cable with f-type to rca adapters on the ends to get the video from the booth to sidestage, where the tv-and-video-cameras contraption will be.
(got the idea from http://maybevideodoes.de/sites/mosaic.html and we've tested it out on a small scale. the scan lines look really cool and the refresh rate wasn't an issue.)

to project onto a screen at the back of the stage, we're going to mount a projector on the proscenium bar, using a projector mount made for mounting on trusses. again, coaxial with rca ends to get the video from the booth to the projector.

the other projector is to be rear-projected. i've never done it, but apparently wax paper works well for a screen. the guys making the set pieces and the pyramid to hold the tvs are making the screen and all that.

i'm going to be making my own video matrix, because i want to be able to output video from any of three dvd players to any of the three screens (treating the tv wall as a single screen). to make the video matrix i'll be using one three-way video splitter, one rca y-adapter, and three three-way input selectors (leaving one input blank).

with that setup, i'll be able to have one image on each screen, the same image on all screens, or any combination of two on one and one on the other.
i.e.
111
121
123
211
113

the only thing i haven't figured out yet is how to send a blank signal to the projectors, so that they won't go to a 'no input' message or something. i think i heard once that you can send audio into the video input and it will just give a blank image. is this true? is there a better way to send a dummy blank signal?

any suggestions anyone has would be great
thanks

p.s. we're pretty settled on the cameras-and-tv method for the video wall. everything else was too expensive (though we were close to using a linux cluster; big tvs are easier to find than computer monitors).

[Footer]

I would spend some cash and rent a video mixer, doing an ABC switch for switching live video is going to drive you up a tree, and the projectors/TV as well. Each time you switch video the projecter will have to re-sync to that source, you WILL get video jumps, and possible blue screens. Remember, ABC switches are just simple contact closures. I am also concerned that you are going to lose your video signal with all that splitting and cable runs, might want to look into some composite amplifiers. I would also take a long and hard look at the wax paper screen thing, paper products have high and low spots, I don't think its going to look the best for an RP screen.

You might also want to attempt to go to PC based content instead of DVD, I think you might be much happier. You can get 3 pc's, link them together using a program called synergy, http://synergy2.sourceforge.net/, and be able to cue them all at the same time. Either that, or put the same content on all 3 DVD players, and only cue the one you need at the time. So, DVD 2 and 3 would have the content that would be played from DVD 1 when you want the same content on all 3. That would take out a lot of the difficulty.

Just a side note, real world you would use a watchout system to do this, this is what that technology was made for. I would also be interested in seeing what the video wall thing turns out looking like. Also, keep in mind "video black", no matter what you send those TV's and projectors, they will still be spitting out light, so blackouts will not be possible in this production without dousers on everything.

[AberNStein]

thanks
re: the switcher and the projectors, we may well have to rent a video mixer. good point.
re: signal loss, my plan is to try it out and if necessary buy a couple signal boosters. i know for the projectors if the signal's not strong enough they won't display anything.
re:wax paper, i'm skeptical too, but it's not my job to make that happen. i just know right now they're looking at stuff that's cheaper than buying/renting a proper RP screen.
re:video black, I think we'll be ok; as far as I know, there aren't any blackouts called for, and the transitions will be videos.

thanks again

[Van]

My only input on this will be on the screen, there are much more qualified Vidiots < no offense intended, it's like "crescent wrench", a trade name> I have extolled, on many occasions, the virtues of Tricot < Tree-coh>. It's a stretch fabric, great for front or rear projection. It's cheap, available in many colors, and widths. You might really want to suggest this to the carps building your screen. It can usually be found in the Wedding, or Undergarments department of any decent fabric store.
I'd say it sounds like you've put a lot of thought in on this project, I'd love to see a ground plan of the set and a little more in-depth explanation as to how the video will be used in this production of the "Scottish Play".

Make a post in the new members Forum and tell us a bit more about yourself and your theatre.

[AberNStein]

thanks
i've passed on your suggestion about Tricot

the idea behind our production is that the witches represent the Media (specifically, their influence on Mac == the everpresent influence of the Media upon youth in today's society)
the play will begin with a 'video overture' (war footage, tv commercials, etc.), and the video screens will be used throughout the play as backgrounds and to set up the atmosphere of each scene.
Banquo's ghost will appear on screen, and the witches will be doing scary stuff on the tv wall (as well as appearing on stage)
I think a couple deaths are happening on screen, and possibly a fight scene.

[Van]

Very cool concept.

[museav]

Given the intended use I would be very wary of the screens and their locations. Not only do you want to be sure that the screens and projectors have appropriate physical relationships for throw distance and angles and are of the correct size for the audience area, but it sounds as though light on the screens and maintaining a usable contrast ratio may be a concern.

This is one area where the wax paper screens really concerns me. Other concerns on that include how fragile the screen material is, how well it prevents hot spotting, what kind of viewing angles you get and what it does to the light output from the projector. The overall issue is making sure that the entire audience can see what is on the screens and not have it washed out or impossible to tell what it is.

The video 'wall' idea is interesting. I looked at the link you provided for the concept and it sounds like it is not actually a video wall where you split an image across multiple screens as much as it is ten different shots of the same image; different angles, portions of the image, etc. If this is wrong and the idea really is a video wall with a single image across multiple displays, then there may be some problems with the proposed approach.

Another consideration is that the application shown in the link provided was for a single person viewing from a short distance from the displays. Not knowing anything about your venue, you may want to consider how that translates to a larger audience. It is possible that some audience member further away may not be able to discern much from the images, they may just be a blur of color and brightness. It is even possible that this could become more of a distraction for some, not really being able to discern the images but drawing them away from other activities on stage. This is very venue and application dependent so it may not be an issue for you, but sometimes things that work wonderfully in smaller settings simply do not translate well for larger venues.

As noted, you will have some resyncing occurring at the projectors when you switch between sources. Using switcher/scalers or seamless switchers could prevent this but would also be more expensive and require running RGBHV/VGA to the projectors. The concept of putting the same files on each DVD is interesting, but unless the DVD players are synchronized you would have differences between them.

Which goes to an important point for your particular application, that you may not care about many of these aspects. In fact, having images poorly registered, delays between different images, hot spots, etc. may actually be a desired 'effect' for this use. And you may not care if the effects differs over the audience area. The one area that may be of concern is making sure that the images are easily visible over the audience area so you might need to verify the screen material, projector brightness and locations and how lighting and set pieces impact the projected images.

[AberNStein]

as i understand it, they'll be experimenting with the rear projection screen until they get something useable and cheap. i've never built a rear projection screen (let alone set one up), but we'll be able to control the light hitting it, so contrast should hopefully be OK

the image quality and definition on the 'tv wall' is not an issue. figures and faces will be discernible, and the 'grungy' look of a video camera filming a tv is exactly what we want

the only thing i'm really concerned about right now is the input switching for the three screens. i may well have to get just one continuously playing dvd for each screen, and then put them all in identical dvd players and press play with a remote to synchronize.
i feel like i'd need to rent three video mixers to do what I need

[Footer]

Originally Posted by AberNStein

as i understand it, they'll be experimenting with the rear projection screen until they get something useable and cheap. i've never built a rear projection screen (let alone set one up), but we'll be able to control the light hitting it, so contrast should hopefully be OK
the image quality and definition on the 'tv wall' is not an issue. figures and faces will be discernible, and the 'grungy' look of a video camera filming a tv is exactly what we want
the only thing i'm really concerned about right now is the input switching for the three screens. i may well have to get just one continuously playing dvd for each screen, and then put them all in identical dvd players and press play with a remote to synchronize.
i feel like i'd need to rent three video mixers to do what I need

Give the DVD players a try, its worth it. You can even cover up the IR reciever on one if you need to play two, it works...

[museav]

Perhaps I misunderstood, but is a continuous signal from the DVDs practical? Is the show timing such that everything else can match to the DVDs? It would seem to be potentially awkward during rehearsals or if something happened during a show.

Speaking of which, if you have to stop or pause the DVD players, will they stay in pause indefinitely or do they stop after a short time, causing you to recue them all? How would you cue and control the DVD players? This may be planning for "what ifs" but it is one area where a real matrix router would be beneficial as you could have one local monitor that could be fed from any DVD player for cueing and monitoring.

You also did not mention how you are addressing audio related to the DVD sources, are the three switchers handling that or are you running each DVD output directly to the mixer? With the DVDs continuously running the latter approach might mean muting different DVDs at different times (you don't want three sources of the same audio active) or maybe putting all the related audio on one disc.