_,,,^..^,,,_ said:

At the end, I found "the peace of mind" thanks also to all your feedbacks, and now I want to follow a new philosophy, "less is more"... in other words, use as few filters as I can - to not overprocessing as I did with my former script.

But, anyway, should I add a derainbow filter?

If there's rainbowing, then I'd give it a try. I've had limited/poor results using some of these filters in the past, and I believe if your comb filter is doing a good job then you should have minimal rainbowing already.

With laserdiscs, after median/averaging captures, I simply use DeGrainMedian for noise reduction (and it does a nice job for the most part), Msharpen used subtly to bring back some small details, if I upscale then a combination of nnedi3_rpow2 and a Spline64 or 36 resize, depending on my needs. If there is visible colour banding then a dithering filter (like GradFun3) can help.

I occasionally add and remove filters as needed, but those tend to do a nice enough job. Using an MT version of AviSynth helps a lot. If you have a dual core CPU then I'd try it, it should greatly increase your render speed and give that idle core something to do ;)