Luma ringing, halo, raster?

[jssilva]

Hello,

I'm seeking for help to improve the quality of this 20 year old family video clip. I've managed to improve it to this point with avisynth, with which I have a reasonable acquaintance.

The problem now is a luma ringing, halo, raster (I don't know how to call it) that I can't get rid of, despite many hours of searching this forum and others.

Please notice the dark edges on the left side of both child's arms, in opposite direction of the same effect after the bucket. This happens all over the clip when there is a strong high to low luma transition. I guess this has nothing to do with chroma because it is still noticeable when I cut sat to zero. It also happens on the date figures. The picture is my source without even deinterlacing.

It is probably relevant to say this clip was shot with an analogue Canon Handicam Video8 and then unthougtfully copied to a VHS tape to reuse the 8mm tape, from which I captured with a Pinnacle PCTV usb2, a Sanyo 6 head VCR, VirtualDub with utvideo, with which setup I have had good results otherwise.



Looking forward to any help you are able / willing to provide,
TIA
jssilva

[sanlyn]

Without a sample of the actual video it's difficult to prescribe in detail, but the effect shown in the image is halo. Try Dehalo_Alpha for starters.

[jagabo]

Those halos are caused by the analog sharpening filter in the VCR. The best way to get rid of them is to turn down (or off) the sharpening filter in the VCR and capture again. Or use a VCR without a sharpening filter.

[jssilva]

Thank you both for your help.

@sanlyn:
Tried the Dehalo_alpha_mt, played with the settings and concluded it was not designed for such wide halos. It doesn't work for this.

@jagabo:
Went through all the clips, 2 full hours, and concluded that only the beach scene has this problem, I wonder why. Fact is I have some footage which didn't go through the VHS stage and doesn't show this problem, which might lead us to think that the culprit was the VCR used for video8->VHS copying.
But there is also footage that went through the VHS stage, also shot outdoors, which doesn't show this problem. So, no conclusion.
Concerning modification of my VCR, I don't have the schematics and you are talking, probably, of an active filter if not an RC network connected to some dedicated chip which I've not the time nor the will to look for. Thank you, all the same. Anyway, as I said, I had good results with it in the past.

So, if there's no easy way to improve it, I guess I'll just leave it as it is. After all, it's just a five minute scene.

Thanks again
jssilva

[sanlyn]

jagabo has the better idea (don't VCR sharpening down or off). Dehalo_Alpha will work with wide halos, but you have to tweak the settings. FixVHSoversharp gets even wider (works in YUY2 only), can clean left or right oversharpening. Sometimes you just have to experiment the first time around.

However, halos aren't the only problem. Look at the edges of high-contrast objects and you'll see dot crawl and aliasing (jaggies), and a problem on the left edge of the boy's arms.. Both filters mentioned will work on those, but for jaggies you need other line cleaners as well.

[jagabo]

Concerning modification of my VCR, I don't have the schematics and you are talking, probably, of an active filter if not an RC network connected to some dedicated chip which I've not the time nor the will to look for.

No, I meant look for an existing sharpness control and turn it down or off.

[jssilva]

Thank you for your continued support.

@jagabo:
Sorry, I misunderstood you; no, it doesn't have a sharpenining on/off switch, just the usual controls plus a tuner; I guess it's not that good.

@sanlyn:
Concerning jaggies and artifacts, as I said before, that was my source. After getting it through FieldDeInterlace(), levels(), tweak(), RemoveDirtMC(), unsharpmask(), autolevels(), coloryuv() and some crop/resize, I brought it as far as this, which almost satisfies me, if it wasn't for that halo.



Concerning DeHalo_alpha_mt(), I played with all the parameters much beyond the limits the author defines, left and right, with no acceptable results.
Concerning your suggestion for fixVHSoversharp(), I also played with all the parameters, also left and right, and it puzzles me because I can't see any change on the image. I even tried to come down to 10 on the luma contrast detection threshold, with no change at all; I double-checked the clip flow to be sure it doesn't get stucked somewhere; can't be the case because I tried another filter just to test the flow; this is why it took me so long to reply to your posts.

Thank you again,
jssilva

[jagabo]

FieldDeInterlace()

I suggest you use a better deinterlacer. Like QTGMC(). And leave the frame rate at 50 fps for smoother motion.

Concerning DeHalo_alpha_mt(), I played with all the parameters much beyond the limits the author defines, left and right, with no acceptable results.

Try reducing the frame size to 360x576 or 352x576 and playing with dehalo algorithms again. Then resize back to 720x576 (or whatever your final intended frame size is).

[jssilva]

Thank you, QTGMC() seems better.

So, I got everything I had before out of the way and set up QTGMC().convertToYV12() and:

Lanczos4Resize(360,576).DeHalo_alpha_mt(rx=2,ry=2, darkstr=2,brightstr=0,lowsens=50,highsens=50,ss=1. 5).Lanczos4Resize(720,576)

as you said. Played with the parameters but couldn't do better than this, which is nicer than before but still awfull, mainly the left arm (on the right side).

Rx and ry can't be wider because light halo starts to show up. Brightstr should be 0, I think, because originally there isn't bright halo, just dark. Lowsens and Highsens don't make much difference except near the limits. Coudn't understand how ss (Supersample) works.

Thanks,
jssilva

[2Bdecided]

Be careful - you've made the kid's hair look like plastic. (Q)TGMC has this tendency, as does dehaloing (which I've never been happy with), and does limitedsharpen.

In the past, I've managed to create clean sharp pictures that just looked weird - and even less natural when burnt to DVD and viewed on a modern TV. Whereas the original noisy blurry video looked normal (though noisy and blurry!). The "best" compromise is sometimes to leave some of the imperfections in (or mix them back in).

Cheers,
David.