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

Merges back the difference in clipb to clipa and clamps the result. By default all planes are processed. This function is usually used together with MakeDiff, which is normally used to calculate the difference.

Unsharp masking of luma:

blur_clip = core.std.Convolution(clip, matrix=[1, 2, 1, 2, 4, 2, 1, 2, 1], planes=[0])
diff_clip = core.std.MakeDiff(clip, blur_clip, planes=[0])
sharpened_clip = core.std.MergeDiff(clip, diff_clip, planes=[0])