Trying to tame Moire patterns

[grannyGeek]

I doubt there is actually any cure for this (and if not, I’ll just forge ahead) but maybe someone here has a suggestion to improve matters.

Source is vhs retail tape, captured in Vdub with Huffyuv to YUY2.
A few brief scenes have “tv broadcasts” and the film-makers laid on scan-lines to make it more obvious as television. Probably due to the reduced resolution of vhs, these cause a kind of sporadic discolored moire pattern, which is mostly bearable --- but on closeups of faces, it sometimes gives an awful Halloweenish tiger-mask effect.
De-interlace filters didn’t help, because the discoloration is not horizontal, but diagonal streaks.
I tried a number of denoisers, smoothers, and/or blurs, and only managed to soften the picture so that faces look shadowed by venetian blinds.


Here is link for 27 mb unprocessed sample clip compressed with Huffyuv showing the problem. I can make a shorter clip if this file is too big.
http://www.mediafire.com/?fw5icq9mzgh



SCREENSHOTS -- resized from 720x480 to 540x360, just to give you an idea of the problem --
http://img504.imageshack.us/img504/1116/moireef0.png (http://imageshack.us)

[Hellworm]

Did you try defreq?

[grannyGeek]

Thank you. I had not know of DeFreq before.

I see I will have to tweak by trial and error, it is a very compex filter, and I don't understand yet how it works.

Education is a GOOD thing.

Thanks again.

[Mug Funky]

you're probably SOL getting rid of all these patterns. from a signals point of view, this kind of aliasing comes from sampling at a much lower rate than the source (film), and not filtering out the above-max frequencies before capturing. CRT based telecines have this problem a lot.

the point being that once a higher-than-myquist frequency has been sampled this way, it shows up as a much lower frequency in the output. if the camera is moving in this shot, that alias frequency will be changing constantly and defreq will probably not be able to catch it for the whole picture the whole of the time.

there's another filter you can try called "fanfilter" as well that may help you.

[grannyGeek]

Mug Funky, thanks for letting me know about FanFilter.

I gave both filters a real quick try, but haven't been able to find settings that even touch the artifacts.
Maybe this weekend when I have uninterrupted time to study the forum posts and test parameter settings. Many FanFilter posts refer to older versions, and the suggested parameter settings no longer exist.

I wonder if the problem is because FanFilter and DeFreq are designed for broadcast frequency interference, and these discolorations are not caused by that.

At the very least, I'll have a couple of tools available if I have problems capturing broadcast tv, so thank you guys for that.
:)