Film-Tech Forum ARCHIVE: Can I Get RGB into Composit-Only Equipemnt

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Posted by Frank Angel (Member # 248) on 12-13-2004, 01:48 AM:

I have an ancient Advent Videobeam, three tube CRT projector (circa 1978) which, amazingly, still produces a very decent picture that has barely degraded by time from what it was producing when it was new, which was when they were first put on the market -- mine is model 1000. It only needed a green tube to be replaced very early on in its life because of a bad manufacture's batch, and then a flyback xformer a few years later; other than that it simply chugs away, producing a very impressive 8ft diagonal, bright, clear, unpixilated image with real (I mean REAL) blacks. I've loved it since I first got it and hooked it up to a Sony U-Matic 3/4in VCR -- back then there was no consumer video decks of any kind.

It was designed so that almost any parameter that you'd want to tweak is tweakable on site, including an 8x8 matrix grid for aligning the three guns in each of those points for very accurate convergence -- and they are right on the control panel along with volume and the standard TV set video controls.

Unfortunately in those days, even on all but studio broadcast level equipment, composite input was all that was offered; that was considered "high end" compared to RF. My question is this: is there any way (sure there is....I guess I mean any EASY way) to inject either an Svid or even a component signal into this beloved piece of equipment? I really want to keep it until it dies. An interesting recent development with anamorphic DVDs now coming out which make me love it even more: the "Beam" allows easy horizontal control right up on the front. It was intended just as a normal video height adjustment, but it has enough range so that I can "squash" the anamorphic image enough so as correct the anamorphic distortion and produce a "letterboxed" image on the screen, but in fact unlike regular letterbox, it is using the entire raster so in a real sense, it is producing an image that is native 16:9. Now if only I can take advantage of the RGB output from my DVD player....

The VBeam has RGB circuitry that is brought right out to the user controls on top of the unit; you can switch each of the three guns and off and adjust their focus and H/V position. I am hoping that it might be a simple task to introduce the three composite signals right there at those switches.

Any of you serious techies have any ideas?

Or should I just be content with what it is and not try to force it to be something it isn't and wait till I break down and buy my first DLP 16:9 native as its replacement when (and if) my Beam finally gives up the ghost? Ah, sorry Mr. Kloss, bad choice of words....his Advent VideoBeam produces no ghosting.

Posted by Mitchell Dvoskin (Member # 751) on 12-13-2004, 09:10 AM:

At one time, and maybe still, computer stores sold little boxes that took the RGB computer monitor signal and converted it to composite video so that you could display computer images (400x600) on your NTSC television.

There are currently boxes available that convert component video to RGB.

/Mitchell

Posted by Stephen Furley (Member # 1277) on 12-13-2004, 11:30 AM:

Mitchel, Frank is trying to get to get improved quality, by using RGB signals, so putting them through an external encoder to convert them to composite vigeo isn't going to help him, unless the external encoder was of better quality than the one built into the DVD player, in which case he might see a slight improvement.

Frank, there were consumer video recorders available long before 1978. There were several models introduced as far back as the mid to late '60s, but they were very expensive, and almost nobody bought them.

U-Matic was intended as a home format when first introduced, whereas the Philips 1500 machine, was intended more for educational/institutional use, but it was the Philips system which was more widely (still not common) used in the home.

I am sure that you could get your projector to accept RGB inputs, but I don't think it would be as simple a gob as you hope; you would almost certainly need some extra components, and somebody who knows the circuitry of the projector.

Posted by Chris Trainor (Member # 9) on 12-13-2004, 04:30 PM:

An inexpensive way to take SVideo and put it on composite is just buy the little radio shack converter. They are about $20. Obviously the quality level will be slightly degraded going from S to Composite, but that's what happens when it's a $20 and not a $200 product... [Smile]

As for getting RGB into the thing, no idea... there are many places that make commercial converters but they all run $200+. Tho that particular box should be capable of RGB somehow.. since it's an RGB projector... but it would take some digging thru the innards of the box to find out where to properly inject the RGB signal.

--Chris

Posted by Steve Guttag (Member # 268) on 12-14-2004, 12:42 AM:

In Extron's termanology...they make "Scan Converters" that will take an RGB source and convert it to a lesser form (Component, S or Composite).

You often get some sort of control over the picture too.

They are not cheap though

The VSC500 is their current entry level unit

VSC500

Then there is their USP405 that is sort of a swiss-army-knife like tool. Takes most anything in and turns it to most anything out (Composite, S, Component, RGB, SDI).

USP405

Steve

Posted by Frank Angel (Member # 248) on 12-15-2004, 09:28 PM:

Nice units, Steve. I assume these Pro level units MAY give me a better end resultant image, but would I be correct in also assuming that even these sophistocated units are still heavily processing the video signal and processing it downward to composite. I was thinking more on the lines of what Stephen said -- that if the DVD is outputing RGB, then going directly from that output to inputing those signals directly into the projector as RGB -- the proverbial copper wire from point A to point B -- it would be better than sticking any processing in between, no matter how elegant (or expensive).

Stephen is right, I need to find some who knows the circuitry. Luckily these units a physically quite big and heavy and were primarily intended for industrial installations (bars, hotels, etc.) so they were designed to be repaid on-site everything is on pullout cards like dolby units and an army of repair technicans were trained to repair them. I am sure one of these guys should be able to gerry-rig an RGB input for me.

Posted by Steve Guttag (Member # 268) on 12-16-2004, 08:47 AM:

Scan converting is NEVER the best solution for making the image look good....it is just sometimes the necessary solution for some installations. They are also used to get a composite signal for monitoring purposes if a composite signal is not available from the source...of say a computer.

As one looses data...you never really get it back...so if you take an RGB source and down grade it to component...you've already started to matrix the colors...go to "S" and you have lumped all of the color info in one place...once in composite land...you've lost it all and will start seeing the rainbows of the composite signal. Thus, a scan converter should only be used when the installation so dictates...not just willy nilly.

Steve