[SSH4]

Originally Posted by Hotte

I did not experience any relevant color shift with my clips.

Concerning performance Step 1 is very, very fast. 90% of processing time goes into (optional) MDegrain.

I´d be happy if you find things to improve, however I am not experienced enough to translate the code above into Masktools, Tweak or ColorYUV.

It would be great if you could help out with a code example - Thanks!

Looks like you try implement something like this:
Limit amount of overshoot and undershoot from Sharp filter.

src=last
overshoot=4
undershoot=16
blr=0.5

i=src.binomialBlur(varY=blr, varC=0, Y=3, U=2, V=2, useMMX=true)
a=mt_makediff(i,src,u=2,v=2,chroma="128")                                      #equal your substract()
x=mt_makediff(src,a, y=3, U=3, V=3)                                               #equal your second substract() that create Sharp
mt_clamp(x,src,src,overshoot,undershoot)                                         #this line limit amount of previous step no more than +4 and not less than -16 from original pixel value