What filter do I need? Is this artifact halo?

[mikansei]

So I have this DVD with an artifact I haven't worked with yet. I've marked with red circles for you to see the artifact I mean: there's this colored shadow around the characters...
I guess this may be a halo artifact but would really appreciate if anyone could confirm and recommend me a filter for it. Do you recommend dehalo or something else?

[Scintilla]

I think most of those are just crappy chroma bleeding (possibly chroma ghosting?) rather than actual haloing, in which case I'm not sure there's really all that much you can do about it.

I've seen filters that (in the process of trying to correct some other problem) can make chroma bleeding worse, but I don't remember ever seeing a filter that corrected the bleeding.

[mirkosp]

Yeah, there's haloing and chroma bleeding. For haloing you can try something like dehalo_alpha(darkstr=0,brightstr=0.8), whereas for the chroma bleeding your best bet is oversharpening only on the chroma (possibly warpsharpening could help in such a case), so using some strong sharpener within a mergechroma(), since, like scintilla said, there is no filter exactly thought out for chroma bleeding, afaik.

[mikansei]

Thank you for your replies! I tried both dehalo_alpha and mergechroma (warpsharp) with only a slight improvement, barely noticable... :S

[Zarxrax]

The Chromashift filter might be able to help some.
I used to use it all the time on tv captures back in the day, as the chroma was almost always shifted a bit on them. I very rarely found a use for it on dvd sources though, as they rarely had such problems.

[mirkosp]

It's not shifted chroma in this case, tho... just bleeding.

[mikansei]

These are the different tests I've done:

In each picture I've written which filter I've used.






I haven't appreciate any change in the image using dehalo, mergechroma or both together. With Chromashift I've appreciate that the chroma bleeding moves from right to left but doesn't disappear

[mirkosp]

I had just given some basic parameters as a start, you were supposed to tweak them depending on the needs, you know...
Since I have more time now, here's something I put together. Please note that there are more instances of dehalo_alpha at a low strength and with different radii values because they are targeted at different halos and because different strength parameters give different results, so it is often better to call it more times at a lower strength than it is to just increase the strength.

Code: Select all

dehalo_alpha(darkstr=0,brightstr=0.6,rx=2,ry=2)
dehalo_alpha(darkstr=0,brightstr=0.2,rx=2,ry=2)
dehalo_alpha(darkstr=0,brightstr=0.8,rx=2,ry=2)
dehalo_alpha(darkstr=0,brightstr=0.8,rx=1.2,ry=0.45)
dehalo_alpha(darkstr=0,brightstr=0.4,rx=1.2,ry=0.45)
dehalo_alpha(darkstr=0,brightstr=0.6,rx=1.2,ry=0.45)
mergechroma(awarpsharp2(depth=48))

Source Frame:

Filtered Frame:


Values are possibly overdone, especially for the warpsharpening. I suggest you tweak them further.

[Mister Hatt]

Either that dehalo setting is off or there is some luma floating going on. I'm thinking the former as the latter is ridiculously uncommon on a DVD or TV or pretty much anything other than remastered analog B&W conversions with a separate chroma clip, and as far as I am aware there are only like 4 films where people were dumb enough to do that. Maybe try camembert for autohax and pray for lack of jaggies? Tweaking dehalo_alpha is super annoying. Could also be some luma ghosting from the previous frame or field, a bit hard to tell with only the one shot.

[mikansei]

>mirkosp

Oh! Much better indeed! Thank you!
I didn't know I had to tweak it. Filter's syntax is difficult to understand for me. Now I'm reading the filter's tweak options but don't understand what each is for. Anyway, I will start tweaking the options to see which is best.

I have a couple of doubts:
- about dehalo:

Code: Select all

dehalo_alpha(darkstr=0,brightstr=0.6,rx=2,ry=2)
dehalo_alpha(darkstr=0,brightstr=0.2,rx=2,ry=2)
dehalo_alpha(darkstr=0,brightstr=0.8,rx=2,ry=2)
dehalo_alpha(darkstr=0,brightstr=0.8,rx=1.2,ry=0.45)
dehalo_alpha(darkstr=0,brightstr=0.4,rx=1.2,ry=0.45)
dehalo_alpha(darkstr=0,brightstr=0.6,rx=1.2,ry=0.45)
mergechroma(awarpsharp2(depth=48))

do i have to put all the options you have written down for tweaking the video? or i have to choose just one? In case I need all of them, why is that?

- about mergechroma: here it gives a few examples of how to use it: http://avisynth.org/mediawiki/MergeChroma
I used this example for the sample images I posted yesterday:

Code: Select all

Chromavid = SpatialSmoother(2,3) 
MergeChroma(chromavid,0.5)

but I see you have used just mergechroma(awarpsharp2(depth=48)) without using the "Chromavid". Is there any difference?

Frequently, when checking the help information for some filters, I find that the information about how to use the filter is not enough for me to understand since I don't know anything about programming language. Dehalo_alpha or Mergechroma would be an example... By just checking at http://avisynth.org/mediawiki/MergeChroma I may learn the tweaking options posted there but... how can I find out new ones like the one you posted? Do I need to be an expert or how do you guys learn tweaking options not posted there?