Artifacts from a commercial DVD

[Altruo]

Allo

I've just purchased some DVDs that were badly edited and I am trying to find out a way to make them visualy better. There is a lot of artifacts mainly in dark areas and I wonder if there's is anything to do about it.

So far this script give me some acceptable results. But I wonder, you guys as pros, what do you think of that video and what kind of approch would you have on it ? Any recommandations would be highly appreciated.

SetMemoryMax(512)
SetMTMode(5,3)
Mpeg2Source("C:\Users\VTS_01_5.d2v", cpu2="oooxx")
SetMTMode(2,0)

TFM(order=1, mode=1, slow=2)
TDecimate()
HQDeringmod()
MosquitoNR(strength=16, restore=128, radius=2, threads=0)
super = MSuper(pel=2, sharp=1)
backward_vec2 = MAnalyse(super, isb = true, delta = 2, overlap=4)
backward_vec1 = MAnalyse(super, isb = true, delta = 1, overlap=4)
forward_vec1 = MAnalyse(super, isb = false, delta = 1, overlap=4)
forward_vec2 = MAnalyse(super, isb = false, delta = 2, overlap=4)
MDegrain2(super, backward_vec1,forward_vec1,backward_vec2,forward_v ec2,thSAD=300)
MergeChroma(last, aWarpSharp(depth=10))
LSFmod(strength = 20)
AddGrainC(var=1.5, uvar=0.0, hcorr=0.0, vcorr=0.0, seed=-1, constant=false, sse2=true)

Adding grains seem to covers some of the artifacts in dark areas, mainly after compression, but it just covers the problem...

Here's a sample of the video. It's not compressed, it's a zone 2 dvd but comes out as a ntsc video ? The sample is a bit big, but I wanted to show different aspect of it, with different kind of artifact. On a PC screen it's hard for me to see the artifacts, on vcl or mpc-hd the video come out much darker than on my TV so artifact are less visible but so are many of the details (ex. on my pc I don't see anymore the clouds in the dark sky). ON tv screen details come out alright, but artifacts are very bad.

I don't know much about avisynth nor it's filters. I base my self on try and error, so excuse my lack of knowledge...

Thanks for your help