Weird levels from TBC

[JVRaines]

I am working on a reel of EIAJ videotape that is a mere 38 years old. The technical production was poor to begin with and the video is quite unstable. When I go straight into the ADVC110, I get good video levels but lots of dropped frames. So I tried the AVT-8710 TBC. It follows the signal much better, but the levels are blown way up toward white. The processing controls on the 8710 don't help much. Any suggestions? Would a fancier proc amp help?

[edDV]

The original had somewhat high black level



The TBC output has way high gain causing raised black levels and white clipping. There must be a gain control on that TBC or there is a missing termination.

[JVRaines]

Nope, no gain control on the 8710. And it works fine with VHS and U-Matic decks in exactly the same configuration. Do you mean termination on the videotape player? It's an antique with Video Out (UHF), TV (8-pin) and RF (F) outputs. I'm taking the signal from the Video Out terminal; nothing is plugged into TV or RF.

[edDV]

Nope, no gain control on the 8710. And it works fine with VHS and U-Matic decks in exactly the same configuration. Do you mean termination on the videotape player? It's an antique with Video Out (UHF), TV (8-pin) and RF (F) outputs. I'm taking the signal from the Video Out terminal; nothing is plugged into TV or RF.

If it works for other decks, probably not a termination issue.

[2Bdecided]

Here's a guess...

The ADVC110 will AGC the video signal based on the amplitude of the sync pulses.

So if the whole signal level is too high, all in proportion, the ADVC110 will see large sync pulses, and bring the whole signal back down to the correct level.

If you replace the large sync pulses with normal ones (e.g. in a TBC that does this without correcting the overall levels), then the ADVC110 will see normal sync pulses, and digitise the too-high-level video as-is.


It could be a termination issue on the EIAJ deck itself - is it switchable? Can you add a 75 ohm resister somewhere at that end? (Don't blow anything up!).

Cheers,
David.

[JVRaines]

Thanks David. I get what you're saying about the overall level. It doesn't seem like a problem with the deck because some tapes play fine, or even dark.

The AVT-8710 has a small range of adjustments. When I bring down the "contrast," the whites come down at the same rate and turn into gray blobs. Bringing down the "brightness" doesn't expand them either; it just crushes the low end.

Many reviewers have noted that the 8710 isn't much of a proc amp. Do you think a quality amp could help my situation?

[NJRoadfan]

You may be better served with an ancient TBC unit from the early 80s (or earlier!), I wouldn't be surprised if modern equipment is having problems with old video like this. From this page: http://www.videointerchange.com/vintage_video1.htm

"Most modern integrated circuit based TBC's will not lock or process vintage video, owing mainly to the severely deformed sync signals endemic to equipment of that era - plus the vagaries of aging tape. This is one case where a full rack size "vintage TBC" does a much better job than a modern piece of equipment. After all, it was designed to process the typical signals prevalent in it's day and is much more forgiving ! The composite sync tip coming off an old EIAJ machine for example, in many cases only slightly resembles a square wave. Modern day equipment isn't very tolerant of such sloppy signals."

[JVRaines]

Actually the 8710 does a pretty good job locking to the signal. But if the sync is very malformed, it's possible that a less-sophisticated AGC in the TBC is blowing up the gain whereas the ADVC110, with a better AGC, handles it properly. So I'm thinking that I either need a better TBC or some device to shape up the sync/levels before they get to the TBC.

[2Bdecided]

A decent proc amp, or a capture device with adjustable levels, seems unavoidable. At least you'd know you could correct it with one of those, whereas you're just shooting in the dark hoping a particular TBC will work. It would be interesting to try an old school TBC though!

I wonder if it's 29.97 or 30.00 fps? That could cause a headache too - though it's probably not old enough to use the "real" NTSC monochrome frame rate of "exactly" 30fps.

@NJRoadfan - thanks for that fascinating link!

Cheers,
David.

[JVRaines]

Yes, it is old enough! EIAJ was an approximation of the RS170 standard of 30 fps. My player (a Sony AV-8600) can do color, too, but this tape is mono and the deck is set for mono. Switching it to color (which I assume is something like NTSC) doesn't change the symptoms, except to add color artifacts.

I may try the ADVC300 with its built-in TBC and level adjustments. Or I might add the SignVideo proc amp which has a function to normalize sync level.

[lordsmurf]

The ADVC300 won't do anything for you.
The old-school 1980s rack TBC, however, is an excellent idea.

[2Bdecided]

The ADVC300 won't do anything for you.

It'll let him set the levels! Combined with his existing TBC it might be fine in all respects. I agree that on its own there would be no TBC present that will help with such a source.

Cheers,
David.

[sanlyn]

The AVT-8710 has a small range of adjustments. When I bring down the "contrast," the whites come down at the same rate and turn into gray blobs. Bringing down the "brightness" doesn't expand them either; it just crushes the low end.

Many reviewers have noted that the 8710 isn't much of a proc amp. Do you think a quality amp could help my situation?

The AVT8710 wasn't designed as a proc amp. For around $200, it's an excellent TBC. The picture controls are rather basic, but they do help at times and they're clean working.

The image controls can be set to default values by pressing the RESET button for several seconds. Note that if you change any of those settings, the TBC will "remember" them the next time you plug it in, so if you don't reset before turning it off you'll have to do it when you turn back on.

You might note which "System" light is working when you record. If it's on AUTO, the TBC will usually guess what your input is (NTSC, PAL, etc.). Otherwise you have to select the source type yourself. The AV8710 reads several input types, but I don't recognize its buttons as indicating the type of source you describe.

Good standalone proc amps cost $500-plus. Look at the SignVideo PA-1. No, the PA-1 doesn't have a TBC. But it does have a decent level meter that in itself should cost more than the PA-1 itself. Never use a proc amp without an internal or external luma meter. Your eyes can fool you, and if your monitor isn't accurately calibrated you'll set eyeball levels that look OK on your TV but look pretty bad elsewhere.

[JVRaines]

Thanks for the advice everyone. I'm familiar with the button ops on the 8710 and it is in NTSC mode.

Update: I gave the ADVC300 a shot. Like the 110, it properly handles the gain. And its LTBC was actually better than the 8710 on several segments, which came as a surprise. But it still drops a lot of frames, and in fact gets so cranky that it falls out of "play" mode in my capture application.

Putting the AVT8710 back in the chain, I find that the highlights are truly blown all the way to 100 and can't be resurrected. So if I add a proc amp, it will have to go ahead of the 8710 to do any good. Or perhaps I will chase down an old TBC as suggested, though I'm unsure of my chances of finding a decent 25-year-old specimen.

[sanlyn]

I've never had a problem with the 8710 -- well, OK, now and then I get a blue video which I find is cured by unplugging and restarting (saw other comments in the forum concerning that). I've tried others, some more expensive, but always go back to the 8710. Maybe someone in the forum with more egineering expertise can answer that one.

For really problematic tapes, I and many others can't do without the excellent PA-1 proc amp:
http://www.signvideo.com/single_dual_proc-amp_video-processor.htm
Yes, I know. Pricey. I tried others. Then I finally bit the bullet, and never looked back.

[JVRaines]

Okay, I'm convinced. I will try the PA-1 next. When they come back in stock.

[lordsmurf]

The PA-100 for sync?
I don't think that's the same kind of sync.

[sanlyn]

The PA-100 for sync?
I don't think that's the same kind of sync.

The OP mentioned he'd like to look into proc amps, as well as other TBC's.

[JVRaines]

The SignVideo proc amp came today and it makes all the diff! I have much better control of levels, especially with the sync shaper engaged. Thanks to everyone who gave advice.