horizontal white scratches - VHS capture

[Scott L]

Hi,

I'm looking for a way to remove horizontal white scratches from a capture made from an old VHS tape. They're apparently the result of either damaged tape heads, or maybe just the fact that the tape was old and had been played hundreds of times. Here's an example of what I'm talking about -



The scratches are not static - they skip around a lot (but only horizontally) and vary in length from frame to frame. I've tried many VirtualDub filters (e.g. temporal cleaner, dynamic noise reduction, 2D cleaner, etc.), but with no success.

Any advice would be much appreciated. The VHS capture that I'm trying to restore is of a rare documentary, and I'm really hoping that there's some way to remove those scratches.

Thanks -

Scott

[filmboss80]

It's called dropout, and it happens when oxide particles flake away from the videotape. To best minimize, you'll need to play the video out through a Time Base Corrector (TBC) that has a dropout compensator (replacing white lines with video information from the line above or below it). If the expense of such a device is not feasible for you, you might try some other filters for VirtualDub or Avisynth, but I have not seen any that are very effective. The slow, laborious way would be to go frame by frame and Photoshop out the dropout flaws.

Take your pick: 1. fast and expensive, 2. slow and marginally effective, or 3. perfect but extraordinarily labor-intensive.

[davideck]

Have you tried a different VCR? I have tapes that show this type of dropout on some VCRs but not on others.

[vhelp]

As for what might be the cause.. it could be almost anything, or at least any one of the above
mentioned conditions. However, I have come up against this issue myself. And I can say I
know (in my setup) the cause.. was based from using cheap tapes. Back in the last Olympics,
(I think it was the 2 years ago or so) I used the Sony standard brand. There was also the
RCA standard brand. These two were on sale and dirt cheap, so I bought them in buld for
the Olympics. Never again. I couldn't believe how much those streaks bothered me. So, I
can sympithize with you on this matter.

Could you post a (1 sec) short clip..might help you in the long run. Anyway. I seen a plugin
been worked on for similar issues like this though over on the doom9 forums, in one of their
AVIsynth boards.. I think the first one. It shouldn't be hard to find the discussion.

Anyway. For something like this and vhs, you need the analog capture route.

If you are capturing these tapes from an mpeg encoder I would suggest against it and go
straight to an analog type capture card and set your project for one of the popular codecs
like huffy or lagarith for near lossless images. Then, you stand a better chance at restoring
the tape for what it is. As good as a hardware mpeg encoder is, it still leaves a multitude of
mpeg macro blocks and pixelation and dct type errors, etc., and you want to remove that
variable, otherwise you will be contending with two problems to solve.

-vhelp 4740

[Scott L]

Thank you for your replies. Unfortunately, I don't have the tape from which the capture was made, so I can't do a re-capture.

I'm afraid that manually repairing the dropouts frame by frame might be the only solution, but that would involve working on several hundred thousand frames and would be impractical.

[lordsmurf]

Have you tried a different VCR? I have tapes that show this type of dropout on some VCRs but not on others.

This was the correct answer.

[jagabo]

I have a VCR that sometimes produces "comets" like that. A few whacks on the side make them go away.

[lordsmurf]

I run a "tape cleaner" through one of mine. It's not actually cleaning anything, but it does make it behave better on the real tapes about 90% of the time. I've never had time to try and figure out why that is.