Quantcast Advanced VCR adjustments for VHS capture? - digitalFAQ Forum
  #1  
12-29-2012, 10:52 PM
JasonCA JasonCA is offline
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Some VCR's have advanced VCR adjustments that are not easy to adjust. For example:

1) SYNC Phase
2) SC Phase
3) Y/C Delay

To adjust these, I would need to use a Phillips head screw driver since there is no knob. But my real question is first, what do each of these three do?

1) What does SYNC Phase do if it were adjusted?
2) What does SC Phase do if it were adjusted?
2) What does Y/C delay do if it were adjusted?

Also, are these adjustments those which you can just eyeball and adjust? Or, if these three on your VCR have not been set correctly, you would have to send the VCR in for some kind of professional calibration? I'm a bit hesitant to stick a Philips head screw driver in to adjust each of these to see what the behavior is.

In terms of Y/C delay, my understanding is that it has to do with the color shifting or bleeding along edges.

Also, is it possible to use test patterns to then adjust the "Sync Phase", "SC Phase" and "Y/C delay" at least for testing purposes to get the VCR calibrated as closely as possible?

Or?
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  #2  
12-30-2012, 11:51 AM
juhok juhok is offline
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As far as I understand (which in this case might not be so far) Sync Phase and Subcarrier Sync Phase are related to adjusting Genlock and if you don't know what they/that means, you have no need to adjust them. Y/C Delay works like you said I think.
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  #3  
12-30-2012, 04:02 PM
JasonCA JasonCA is offline
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Ahhhh I see. So "SYNC Phase" and "SC Phase" have to do with GenLocking on some external unit. So it has nothing to do with controlling the video signal...which is what I originally thought.

Thanks for your input juhok!
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  #4  
12-30-2012, 07:08 PM
jmac698 jmac698 is offline
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I understand what these terms mean, but I don't know why you had to adjust them, in the 80's workflow.

y/c delay will shift the color relative to the b/w version of the image. The colors are much wider than the edges, so a good compromise is to align the colors to bleed evenly on both sides of an edge. This can be done easily in software though.

sc phase means subcarrier phase, which is a fancy way of saying tint. You would use colorbars to adjust this so that the tints of the bars are good. If you can't get a great match, just make faces look the right color. This is also easy to do in software.

Sync phase, my guess is that would move the picture left and right. Use colorbars and make them look centered. This has some use to capture most of the image with your capture device.

To know more, find a manual for any old broadcast video device, like a TBC or VCR. There's a post in another forum with copies of manuals.

If you really want to calibrate these, record color bars from the Avia test dvd, then adjust them in playback. Slight problem, is knowing if the way you're viewing the playback is reliable. You could use an oscilloscope to remove all doubt, or go through a process of verifying the capture device's capture window, and that it's tint settings match a standard etc. For pc capture cards, the capture window varies quite a bit, so you can't really be sure of it. It can vary by driver or be changed by registry settings or UI controls.
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  #5  
12-31-2012, 02:23 AM
JasonCA JasonCA is offline
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Quote:
Originally Posted by jmac698 View Post
I understand what these terms mean, but I don't know why you had to adjust them, in the 80's workflow.

y/c delay will shift the color relative to the b/w version of the image. The colors are much wider than the edges, so a good compromise is to align the colors to bleed evenly on both sides of an edge. This can be done easily in software though.
Ok, so it sounds like I can leave this to software then to correct.

Quote:
Originally Posted by jmac698 View Post
sc phase means subcarrier phase, which is a fancy way of saying tint. You would use colorbars to adjust this so that the tints of the bars are good. If you can't get a great match, just make faces look the right color. This is also easy to do in software.

So this "SC Phase" does not have to do with an external source then. It does modify the video...in this case...help to correct the tint levels. But again, sounds like I can also leave this for software to correct.

Quote:
Originally Posted by jmac698 View Post
Sync phase, my guess is that would move the picture left and right. Use colorbars and make them look centered. This has some use to capture most of the image with your capture device.
Ok, in genrel, it sounds like the SYNC Phase adjustment is then sort of like the controls are your monitor/lcd (one of my LCD displays call it the H-Position). You can move your window left or right to help ensure what you want to be captured.

Quote:
Originally Posted by jmac698 View Post
To know more, find a manual for any old broadcast video device, like a TBC or VCR. There's a post in another forum with copies of manuals.
I will continue to investigate this.

Quote:
Originally Posted by jmac698 View Post
If you really want to calibrate these, record color bars from the Avia test dvd, then adjust them in playback. Slight problem, is knowing if the way you're viewing the playback is reliable. You could use an oscilloscope to remove all doubt, or go through a process of verifying the capture device's capture window, and that it's tint settings match a standard etc. For pc capture cards, the capture window varies quite a bit, so you can't really be sure of it. It can vary by driver or be changed by registry settings or UI controls.
You raise a good point. Isn't it true that even if you calibrated your VCR to spec, there can be VHS tapes that were recorded out of spec whereby you would need to make adjustments for a specific VHS tape on the VCR on a case by case basis? I suppose what you are saying is the calibration helps to make sure the VCR does what it should do according to some spec first. But, you don't necessarily mean the each VHS tape you use as a source will adhere to the spec due to most VHS tapes having not been recorded correctly to the spec to begin with.

Also, based on what has been said, it seems like I can leave "SYNC Phase", "SC Phase, and "Y/C delay" alone then once they have been set correctly? I don't need to adjust them on a tape by tape basis. I suppose that's why those require a Philips head to adjust them. If anything, it seems like I can make corrections to these 3 via software?

The other controls actually have nobs that I can turn...which are "SET UP", "CHROMA" and "HUE". It seems like I would need to adjust these last 3 on a per tape basis?

I'm trying to establish, if possible, what I should be fiddling with on the VCR each time I capture from a different VHS sources. And, I'm trying to establish which ones I can adjust and eyeball and which ones I should only adjust via perhaps a test pattern or otherwise.

I've still not played with the "SYNC Phase", "SC Phase" or "Y/C delay" on the VCR out of fear I would not be able to set it back to what it properly should be.
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  #6  
12-31-2012, 06:25 AM
juhok juhok is offline
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"SYNC Phase", "SC Phase" and "Y/C delay" might only affect recording, ie. calibrating the VCR to the feeding device. This is how it's done in many manuals in other devices. Turning them might not affect playback picture at all, unlike CHROMA and HUE knobs which will probably have an effect.

Even if the phase knobs worked, you're correct that home made VHS tapes are all over the map and fine tuning these settings will not help you much if not at all even if they did something. CHROMA and HUE can be adjusted per tape basis depending on your taste or left at unity gain and do it in software later.

jmac698: In the analog workflow you had to adjust them because not every - if any - device was built and kept 100% to the spec?
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  #7  
12-31-2012, 11:30 AM
jmac698 jmac698 is offline
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Similar thoughts here, when you mentioned the separate tint control I started thinking I didn't quite get it right.. well, I think those controls are for making two analog signals closer in spec in order to mix them together, like fade between two sources.

https://en.wikipedia.org/wiki/SCH_Phase_Display

Now I think that changing this would have no effect, if the tint is measured relative to the color burst whereever it is. It makes a difference mixing because the sources are literally added together, so they have to be perfectly in sync or they could partially cancel each other out.
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  #8  
01-01-2013, 09:56 PM
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Yea, that makes good sense. I don't have anything to add to that really.
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