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  #16  
Old 05-06-2008, 12:11 AM
andy andy is offline
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  #17  
Old 05-06-2008, 07:31 AM
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Quote:
Originally Posted by t0nito View Post
Good thing we in "PAL" land don't need or have any tint controls. Colour is natural as it should be...
Although PAL does correct for phase errors, it comes at a substantial cost. The phase errors are replaced with saturation errors, which if bad enough become Hanover Bars, and the PAL system cuts the vertical color resolution in half. With the stability of modern equipment, NTSC can actually provide a better color picture.
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  #18  
Old 05-08-2008, 02:10 PM
Ralph S Ralph S is offline
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This is for Jeff: The VIR signal you're talking about was usually generated at the station or mastering house using a Tektronix 1441 VIR signal Deleter/Inserter. The signal could be inserted on line 19 or 20 to give an absolute reference for amplitude and phase characteristics of a color TV program or recording. The signal placed a sample subcarrier burst of 40 IRE at 70% video level followed by a sample unmodulated 50% video pulse on the selected line. The receiver could use these two samples to lock the color reception of the set without worry about transmission distortions which might occur at or near "0" IRE where line burst reference is placed in NTSC. In essence the VIR signal was placed well above sync/subcarrier and the potential distortions which can occur in analog broadcasting.
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  #19  
Old 05-10-2008, 10:13 AM
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The original thought with VIR was that it could be inserted early in the signal path and allow correction for all that happened along the way. But then people started to reinsert it along the way, and I believe, even just before the transmitter so that it could be used to adjust the transmitter. Of course, it had no relation to all the preceding distortions then, and became useless in a consumer set. I remember doing competitive analysis of a GE set some time after VIR had been around for a while, and much of the time you would prefer to turn it off.

[EDIT - I mean turn off the VIR - but maybe you would prefer to turn off the set too! ]
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  #20  
Old 05-10-2008, 12:57 PM
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Quote:
Originally Posted by old_tv_nut View Post
The original thought with VIR was that it could be inserted early in the signal path and allow correction for all that happened along the way. But then people started to reinsert it along the way, and I believe, even just before the transmitter so that it could be used to adjust the transmitter. Of course, it had no relation to all the preceding distortions then, and became useless in a consumer set. I remember doing competitive analysis of a GE set some time after VIR had been around for a while, and much of the time you would prefer to turn it off.

[EDIT - I mean turn off the VIR - but maybe you would prefer to turn off the set too! ]
My great-uncle had a GE TV with VIR in the early 1970s--the first television with that feature I ever saw in my life (haven't seen another since, even on eBay). I don't honestly know, however, if he even knew the feature was there. This frequently happens with functions on TVs such as auto-color, VIR and the like--people just turn on the set and watch their programs, with little or no regard for those extra buttons, knobs, etc. for other functions (this also applies to Sears Silvertone's "Chromix" control on a few of their higher-end sets of the '60s-'70s that was supposed to inject a soft blue hue into monochrome pictures; most people simply set the control to black and white and forgot about it). It's just as well; most auto-color correction schemes didn't work all that well, as has been discussed in this thread previously.

Most if not all color televisions worked better with these systems turned off and disregarded, anyway. I shut off the auto-color control on my RCA CTC185 some time ago as it isn't needed, given today's rock-stable chroma circuits in the sets themselves (all televisions manufactured in the last decade or so, not just RCAs) and the vastly improved stability of the signals from TV stations, especially if you are on cable.
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  #21  
Old 05-10-2008, 01:10 PM
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Did anyone even insert the VIR signal? Does anyone even do it anymore?
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  #22  
Old 05-10-2008, 01:51 PM
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Not to incite the debate between PAL and NTSC, just remember, People Are Lavender.

With digital processing and transport in the signal path to the average consumer receiver, NTSC is vastly better than in the past.

I can't however stand artifacts of digital compression. Don't even get me started on message crawls and dogs/bugs on the bottom of the screen.
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  #23  
Old 05-10-2008, 02:22 PM
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The first set I saw with VIR was a mid to late '70's GE console. I think it used the "YM" chassis. I also saw a Curtis-Mathes with the feature. On both sets, the picture looked better with VIR turned off. It was sometime in the mid '90's when I had these sets. Most of the "auto color" systems I saw were a switch that would disable the front panel adjustments and enable preset controls that were hidden inside the set. In some sets, the user controls would have limited effect with the auto color switch on. Our old '77 RCA ColorTrak 19" had a photocell that would adjust the picture according to room light. I think RCA continued to use the photocell in their better sets up until the early '90's. I've ran into plenty of Thomson era RCA's that have an auto color setting in the user menu. I really couldn't tell any difference in the picture no matter if it was on or off. Like has already been said, most TV broadcast signals are much more stable with less error than they used to be.
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  #24  
Old 05-10-2008, 11:02 PM
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We had a GE VIR set in the 80s; I never saw a great difference either way. (I was never crazy about that set; I preferred its tube predecessor) I have also seen ads for "VIR II" but I don't know the scoop on that.

Did you know that the General won an actual Emmy award for VIR?
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Last edited by bgadow; 05-10-2008 at 11:04 PM. Reason: clarify
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  #25  
Old 05-11-2008, 02:10 PM
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Quote:
Originally Posted by bgadow View Post
We had a GE VIR set in the 80s; I never saw a great difference either way. (I was never crazy about that set; I preferred its tube predecessor) I have also seen ads for "VIR II" but I don't know the scoop on that.

Did you know that the General won an actual Emmy award for VIR?
Bryan, I found some information (by doing a Google search) on GE's VIR/VIR II automatic color correction that seems quite interesting; it describes what the VIR (vertical interval reference) signal actually was and its effect on the TV picture (on GE sets equipped with VIR processing circuitry, of course). The VIR signal itself was inserted in the 19th line of each field of video and was quite simple, only containing a chroma reference, luminance (Y) reference, and a reference signal for black level. The TV's VIR decoding circuitry used this signal to correct the differences, if any, between the references in the VIR signal and the tint, color and brightness of the transmitted TV signal. GE hailed this system as one that would truly automate color level tint and black level adjustments (requiring no intervention on the part of the viewer), but it didn't quite live up to its expectations; as a result, the feature was dropped from GE TVs a few years later. I don't know much about VIR II, the second generation of the original VIR system, but I don't think it was that much better than the first. As I said in my first post regarding VIR, most viewers probably did not realize the feature existed on their GE televisions; even if they knew the VIR on/off switch was there, they did not pay much attention to it, leaving it set at the off position. The Chromix control on many high-end Sears Silvertone TVs of the '70s was treated the same way by most set owners; the control injected a soft blue hue into monochrome pictures, but most viewers found the adjustment confusing, too critical in most cases, and not of much value, so they usually just set the control to black and white and forgot about it. The same thing happened with most auto-color correction schemes; the viewers just watched their programs, with little or no regard for the extra buttons, dials, etc. on the front panels of their TVs. I know at least one person who does not bother with the color controls on her TV--she just turns on the set, watches her programs, and turns off the set when the shows are over. That's it. She doesn't know or care about anything else regarding her television set or how it works.

GE's VIR system was a novel experiment, but it just didn't catch on with the viewing public. In fact, I'm downright surprised the system won an Emmy, since it was nowhere near the greatest thing to happen to television since color. For that matter, IMO, neither was RCA's ColorTrak system, which did not rely on signals transmitted in the vertical blanking interval but used a photocell under the CRT to adjust color and black level according to room light conditions. Magnavox, in its high-end color consoles of the '70s, had a similar system it called "Total Automatic Color" which also used a photocell to adjust the same parameters of the picture, again according to room lighting conditions. These systems, however, were not infallible; the ColorTrak system, for example, could well be "fooled" into raising the black level abnormally high (taking the color saturation with it) if, again for example, the set were being viewed in a dark or dimly-lit room. I hate to imagine what some of these ColorTrak sets' pictures may have looked like under such lighting conditions. There are people who enjoy watching television in the dark, much to the horror of eye doctors, who have been warning people for generations against watching TV in a totally-darkened room because of the very real risk of eyestrain. I guess, however, that most people who insisted on watching their TV sets in darkness or dimly-lit rooms would just turn off the ColorTrak or TAC functions of their sets, or, if they left them on, tolerated the horribly overbright, oversaturated color picture that likely resulted when the circuits were bamboozled into lowering the CRT bias to near zero and raising the color level to maximum.
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  #26  
Old 05-11-2008, 02:28 PM
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I am glad most or all of those "automatic"/dynamic circuits and buttons are long gone. A display device should be properly adjusted, once, for correct levels, and then left alone until it might need recalibration. The room lighting should be adjusted to allow for good display viewing, not the reverse.
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  #27  
Old 05-11-2008, 03:20 PM
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  #28  
Old 05-11-2008, 03:38 PM
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Degauser?

I remember using a little round plastic degauser that I plugged in to the wall outlet on my folks first color tv (RCA), about 1966. It was always fun to watch the weird color patterns it caused, but I'm not sure it really did anything?
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  #29  
Old 05-11-2008, 04:59 PM
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Quote:
Originally Posted by tubesrule View Post
Although PAL does correct for phase errors, it comes at a substantial cost. The phase errors are replaced with saturation errors, which if bad enough become Hanover Bars, and the PAL system cuts the vertical color resolution in half. With the stability of modern equipment, NTSC can actually provide a better color picture.
You should not forget that the stability of modern equipment does also reduce saturation errors of the PAL system. But the halved vertical color resolution is the disadvantage of PAL. Especially when you watch a video recording of a PAL broadcasting.

But on the other hand, the color subcarrier of PAL is 4.43 MHz, the color subcarrier of NTSC is only 3.58 MHz. PAL does provide a much larger video bandwidth, and together with 25 frames per second, while NTSC has nearly 30 frames per second, the horizontal resolution is much better than with NTSC.

If you watch the same video content with a PAL and with a NTSC receiver, you will find the PAL display much sharper and detailed than the NTSC display. On the other hand, with larger displays, you can notice more flicker with PAL.

The color reproduction of NTSC with a proper adjusted NTSC color tv set might be much better than with a PAL set due to the higher color resolution.

- Eckhard
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  #30  
Old 05-11-2008, 10:26 PM
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Quote:
Originally Posted by rek100 View Post
I remember using a little round plastic degauser that I plugged in to the wall outlet on my folks first color tv (RCA), about 1966. It was always fun to watch the weird color patterns it caused, but I'm not sure it really did anything?
They are an important tool in the repair of older color tv sets, to remove any magnetism from the crt. By the late 60s all but the cheapest sets had built-in automatic degaussing. A magnetized screen will have blotchy color, so that a picture that is supposed to be all white will have some pink in one corner, some green up top, some blue over on the other side, etc.

I discovered that the crt monitor on my work computer has a manual deguassing feature in the on-screen menu. So when I get really bored I will go on and do it, just to see the special effects!
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