[INFO] DeRing vs DeHalo?

[shijan]

I usually prefer do not use DeHalo filters because they are known for additional artifacts, especially if there are huge solid black areas or black frames. But same time i really hate those oversharpened edges on DVDs and DVs. So i experiment with DeRing filters and seems they clean up things way better.
Just curios what is the fundamental difference between DeRing vs DeHalo? They seems do the same - detect edges and filter things around them somehow.
So what are "correct" situations to using each of those filters?
Any risks if use DeRing as essential filter for DVDs (in similar way as Deblocker)?

Here are some examples (SD upscaled to 1080p with NNEDI3):

[Selur]

Halo: A bright ring (halo, the thing angels have above their head)
Halos in digital video: A bright ring around edges (caused by edge enhancement)
Ringing: Noise or unwanted alteration around edges in general
Ringing in analog video: Edge-echo/ghost (but not caused by edge enhancement)
Ringing in image/audio compression: High-frequency distortion caused by quantization

They are very similar. "ringing" usually refers to Gibb's phenomenon occuring within DCT blocks (or other transforms, like in wavelet or h.264 codecs which aren't only 8x8 DCT), where "haloes" are most often caused by some kind of frequency filtering, either in analog or digital (oversharpening).

Halo is usually the white/black additional line around an edge.
Reinging is usually reffered to as moving noise around edge.

But they often look quite similar and are often used to describe the same visual effect.

Just curios what is the fundamental difference between DeRing vs DeHalo?

DeRinging is usually more aggressive than DeHalo, also DeHalo mainly aimss to remove the halo itself and not necessarily the

So what are "correct" situations to using each of those filters?

If you don't have rining, usually you should not apply de-ringing. If there's no halo do not apply dehalo.
If you only have a halo try first dehaloing filters, if they are not aggressive enough try deringing filters.
If you only have ringing, use a ringing or denoise filter. (ringing filter = basically a masked filter)

Any risks if use DeRing as essential filter for DVDs (in similar way as Deblocker)?

Like (basically) all filters they destroy/change image information, so yes blinbly applying filters without cause is not a good idea if you want to preserve details/information.

Cu Selur

Ps.: There should be tons of documentation about this on the net.

[zspeciman]

I'm glad to have found this topic.  I need some guidance on this subject.  Source is analog VHS-C tape.  Attached is a short clip and image capture
Is this Halo?  It effect both sides of the column. 
If it is Halo, what DeHalo settings do you recommend to use?
If I have several tapes from the same camcoder, will a single setting apply to all tapes or it is different for each scene?

[Selur]

I do not recommend using this source.
Looks like some capture where tons of sharpening was applied, that caused ringing and halos, so I would re-capture it. (and turn that damn sharpening off)
I would probably start with some masked aWarpsharpen + DeHalo_alpha +Santiag + DPIR
image: https://imgsli.com/Mjc3MjE3
script: https://pastebin.com/96gpQKUb
the values are used need to be tweaked.


Cu Selur

[zspeciman]

Thank you so much for working on this clip and your advice, you're a true video guru.
It works quite well for the clip.  Once faces are introduces in the video (not included in this clip) it doesn't do as well.
Best to recapture it as you've suggested.
I was using a simple usb device WinTV-HVR-950Q with the wintv software.  Looking thru the software menu I couldn't locate any sharpening, enhancement etc.  I didn't see it in the vcr either.  I was trying to capture it as raw as possible.  I am wondering if it is the limitation of the capture device, the vcr itself, the bad settings on the camcoder when the video was taken, or the capture software. 
Is there a video capture software that is the "go to" gold standard that you recommend?

[Selur]

About capturing&co best look over at https://forum.videohelp.com/forums/41-Restoration or https://www.digitalfaq.com/forum/video-restore/ both have lots of members who can better advise on this.