This Blu-Ray I am working on is getting artifacts in the Reds or certain places for some reason. These are only appearing after I descale it and rescale it with a less soft scaler.
Here is an example comparison image.
Just look at the black lines in her hair where the shadow is around her neck area. For some reason, there is what looks like spreading white appearing all over those lines. It seems to be most visible in the reds and that's the only place bothering me. A dehalo filter is not really helping it. I am assuming this is a chroma based issue, I'm not sure.
Is there a reason for this and anything I can do to stop it?
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Last edited by killerteengohan; 16th Nov 2019 at 07:00.
Those are oversharpening halos in the chroma. If you look at the U and V channels with UtoY() or VtoY() you'll see them all over the place.
I kinda figured the debilinear filter was doing a fairly strong sharpening job. I had to use that mask around the edges to hide those halos lines around the entire outer rim of the video. Ever since I learned about that edgemask from you, it's been a big help on things.
Can I still use that debilinear filter and somehow reduce the visibility of them appearing on the reds after its used? I tried dehalo alpha, but it didn't really reduce it any it for me. Some kind of mask perhaps?
You could merge the original chroma (maybe sharpened a bit) with the new luma.
What would I add into to the script to try that?
Something like MergeChroma(last, source), or MergeChroma(last, source.awarpsharp2(depth=5)), somewhere after Overlay().
I was actually already trying, and using mergechroma(awarpsharp2(depth=3, blur=1, type=1)) at the end. It helped, but barely.
Adding MergeChroma(last, source.awarpsharp2(depth=3, blur=1, type=1)) to the end worked quite well. It looks somewhat softer overall, but it actually looks nice and I will use this. It ended up pretty much perfect to me. Thanks a lot for that!!
Just out of curiosity. Is there another way to sharpen the chroma a little more to help the softness some? When I raise the depth more, colors start getting smeared out place slightly, by moving/bleeding out of lines/edges, and once it reaches a higher setting like 20, it's ruined. Is mergechroma the only way to sharpen chroma?
There are many sharpen filters: http://avisynth.nl/index.php/External_filters#Sharpeners . But keep in mind that YV12 chroma is sampled at half (each dimension) the resolution of the luma. So chroma and luma edges will never match perfectly.
Last edited by killerteengohan; 21st Nov 2019 at 08:15.
I mentioned this is post #2: UtoY() and VtoY().
For YV12 I often use:
StackHorizontal(GreyScale(), StackVertical(UtoY(), VtoY()))
StackHorizontal(GreyScale(), UtoY(), VtoY())
Oh, there's one other technique I occasionally use...
You can't see true colors without the luma component. But you can get a sense of what the colors look like without the luma by setting the luma to a constant value:
ColorYUV(off_y=-255).ColorYUV(off_y=64) # force all Y to 64