Black flecks on video tape?

[Hushpower]

Hello again all,

I would be grateful if I could have some opinions on what may be the cause of the black flecks in this screenshot of a VHS tape capture?

For example, tape, VCR, ES15 (I have NR off), capture card or Virtual Dub/Lagarith codec. Also, can it be corrected with a filter in VDub? It doesn't occur on some parts of the tape, which is a mish-mash compilation of all sorts of stuff.

Thanks a lot!

Cheers, Al

[hodgey]

This sort of artifact is something can occur during modulation/demodulation of the video signal to/from the frequency modulated signal that is recorded on tape, it's sort of like clipping, but on the RF signal. If it happens only on this section on this tape it may be something that happened when the tape was recorded. If they are on the recording they will show up in the exact same spot every time.

It can have several causes, recording VCR issues, worn video heads, video signal on the being very low, issues with video IC or other VCR components and others. I've found that JVC VCRs in particular can be a bit suspectible to showing these if tracking is off or the video signal is very low. There is some other distortion around the area as well on your image which may be related, so maybe tracking is a bit off.

I would check adjusting tracking on the section has any effect on the specks and noise, and if possible see if you get the same effect in a different VCR.

If it's embedded in the recording, there are some avisynth plugins that can help, like DePulse or (various versions of) RemoveDirt/RemoveSpots though I've never managed to make that work well without destroying detail.

[lordsmurf]

That's often a sign of extreme head wear, if not seen on another deck.

[Hushpower]

Thanks for the replies. I did some experimenting and found if I used the default VDub interlace filter, I could get rid of most of the flecks, so it seems as though they are (depending on the clip) only in one field, if I understand correctly, because they completely disappear if I use "Interpolate using Yadif" and "Keep Top Field". NeatVideo also reduces their effect.

I did try my other VCR, with much worse results, but that is a tracking problem methinks. I've posted on another thread a question about that.

I'll live with the flecks.

-- merged --

I've just pored through the video again and have only just noticed that the flecks are mostly in a band of very faint static lying horizontally across the screen, about 20% below the top. I'll look at fiddling with the tracking (as mentioned by Hodgey).

Thanks.

[lordsmurf]

I have Avisynth scripts to near-completely remove the issue from interlaced footage. But note that it's a powerful filter, and can just as easily cause more damage if not tweaked properly. Must be used on small sections, the reviewed carefully.

If you're seeing this on only 1 field, I think that suggests head damage is likely.

Comparison to another VCR, for process of elimination, is needed.

Deinterlacing is not really the solution.

[Hushpower]

Thanks everyone, I'll look for another VCR to compare. I did adjust the tracking on my good VCR, but the flecking effect didn't go away. I suspect it may have been put on the tape by the original machine.