Home Free Library Store
Free Catalog



Save with a Two Year Membership

To post in the forums see the Forum Guidelines.
Join or Renew Today.
New Benefits for all VU Members
Forum Guidelines and FAQ
Main Index Search Posts
Who's Online Log In



Home: Video University Forums: Tech Q & A:
Time Base Correction Problem

 
 


22west
New User

Feb 17, 2005, 9:08 PM

Post #1 of 3 (1205 views)
Shortcut
Time Base Correction Problem Can't Post
I am really struggling with this problem.

I temporarily borrowed a JVC SR-VS30U S-VHS to MiniDV Combo Deck to make a digital copy of an old VHS home video. The copy was fine, a nice clean version of the original.

I have some other old tapes so, using my own digital deck, I decided to set up to make my own copies. The setup is as follows:

JVC HR-S2913U S-VHS to a DataVideo TBC-1000 Time Base Corrector to a Sony DSR-11 to a Sony PVM-14L2 Video Monitor.

The copies are coming out distorted. I get waving verticals, see this link for an example:

http://www.videonics.com/graphics/mixing/time-base-errors-x2.gif

The waving verticals were REALLY bad before I introduced the TBC. Now they are slight but they are still there.

Notes:
When I copy a new VHS tape (like a movie from Blockbuster) the picture is fine.
The time base corrector also has full frame stabilization.
When I take the digital deck out of the setup, and simply play the tape on the monitor, I still see the distortion (ie; the deck is not causing the problem).

See the attached image. On the left is a frame grab from the copy made from the combo deck on the right is a frame grab from the copy made using my setup.



Could it be that the TBC is simply unable to handle the poor video signal coming from the old tape?
If so, why was the combo deck able to produce a good copy?
What does the combo deck have that I dont have? Unimpressed


wilebill
User

Feb 18, 2005, 8:50 AM

Post #2 of 3 (1193 views)
Shortcut
Re: [22west] Time Base Correction Problem [In reply to] Can't Post
It's really hard to diagnose a problem like this without being able to see the exact moving images. However, I have a few thoughts.

First, are you using a scope/wave form monitor to check your IRE (brightness) levels? Seeing as that there is a lot of sky in the shot, it could be that it's way over-exposed in some areas, and that may be part of the problem. Do you have a proc amp in the TBC or do you have one available? If so, you may want to bump down the video level and see if that improves anything. It should help with the waving verticals and the flagging.

Secondly, the jumpy picture is more than likely caused by improper tracking, and that may also be the problem with the flagging. Is the bottom edge of the tape creased or stretched? This will also cause those problems.

One other thing to check is the horizontal phase (SCh) of the signal. If your TBC has that setting, try adjusting that a little to one side or the other. I've seen that improve the waving verticals.

Lastly, some VCRs are just better than others at playing back old tapes.

Regards,
Billy Horton
Video Image Productions

Studio & On-Location Video Production
2 NewTek VT[4.6] Editing Suites


videobear
Veteran


Feb 18, 2005, 6:14 PM

Post #3 of 3 (1170 views)
Shortcut
Re: [22west] Time Base Correction Problem [In reply to] Can't Post
A TBC will not correct mistracking problems. If your playback deck has a manual tracking adjustment, try using it to see if you can improve the picture. Many consumer VHS decks no longer allow the user to vary the tracking. If that's the case, try taking the tape down to the local cable or TV station and see if they can help you out with a professional deck.




Regards,
Doug Graham
Panda Productions