std.MakeDiff(clip clipa, clip clipb[, int[] planes])

Calculates the difference between clipa and clipb and clamps the result. By default all planes are processed. This function is usually used together with MergeDiff, which can be used to add back the difference.

Unsharp masking of luma:

blur_clip = core.generic.Blur(clip, planes=0)
diff_clip = core.std.MakeDiff(clip, blur_clip, planes=0)
sharpened_clip = core.std.MergeDiff(clip, diff_clip, planes=0)