Sharpening produce diagonal lines ?

[arminio]

I have B&W VHS source material with very soft picture. I captured it and it loos OK but, as I said too soft. So, I used AviSynth for frameserving and test a two sharpen filer (msharpen and asharp) and both give fine result but with some artefacts - in some scenes, diagonal lines occured!

These lines exists in original source too but they are practically invisible becasue picture is too soft and when I sharpen it, it just make things worser.

Lines look like thos on picture samples at http://www.digitalfaq.com/restoration/video/videorestore.htm

Any ideas how to remove this? I already tried deinterlacing (alhough it is not interlace problem) but without help... are there any AviSynth filters that can fix this?

[Mug Funky]

hmm... interference is a problem. you can cancel it with temporal smoothing, but usually you nuke a lot of the picture at the same time.

i'd love to see some hardcore frequency based filters coded in avisynth, but without sufficient coding or mathematical knowledge, i can't make them (i'm thinking something similar to the statistical FFT noise reduction techniques available in audio).

peachsmoother is good with this kind of interference i think. i haven't used it much on anything but DV material so i can't guarantee that.

[arminio]

>hmm... interference is a problem. you can cancel it with temporal
>smoothing, but usually you nuke a lot of the picture at the same time.

Won't smoothing make picture more soft? This happens after sharpening which I need to make becasue picture is already too soft :(

>peachsmoother is good with this kind of interference i think. i haven't
> used it much on anything but DV material so i can't guarantee that.

I'll try that! Thanks!

[Didée]

You might give a try on LimitedSharpen() (http://forum.doom9.org/showthread.php?s=&postid=482736#post482736). Using this with "soft=true" (important), and either power=0.0 ++ overshoot = 3~5~7~11, or power >= 2.5 perhaps could work out on your material. Or it might not. Be sure to perform a tough denoising peforehand, in any case.

However, your screenshots *after* sharpening to me appear more soft than the input ... perhaps your filtering strategy is, erh, not optimal.


- Didée

edit Wilbert: fixed link :)

edit Didée: Thanks, just saw it ;)

[arminio]

>However, your screenshots *after* sharpening to me appear more soft
>than the input ... perhaps your filtering strategy is, erh, not
>optimal.

These screenshots are not from my material. I gave link only to pictures with simillar problem I have (how diagonal lines looks in some scenes in my material AFTER sharpening).
My material is too soft and I need to sharpen it but then I get visible diagonal lines that does not exists (actually, not visible) in original soft picture.

[jult]

Hey arminio, did you ever find a good filter against this?
I'm suffering from the same problem with converting VHS using an ADVC300 unit. When sharpening is applied, I also increase the constant diagonal stripes that are over the entire screen.

It's weird that there are filters that do a great job on de-interlacing, while an entirely constant distortion like this is not easy to filter out, apparently.. (maybe because it's diagonal, and not horizontal/vertical?)

Anyone?

[Guest]

Try defreq() before sharpening.