Lut2

std.Lut2(vnode clipa, vnode clipb[, int[] planes, int[] lut, float[] lutf, func function, int bits, bint floatout])

Applies a look-up table that takes into account the pixel values of two clips. The lut needs to contain 2^(clip1.bits_per_sample + clip2.bits_per_sample) entries and will be applied to the planes listed in planes. Alternatively a function taking x and y as arguments can be used to make the lut. The other planes will be passed through unchanged. By default all planes are processed.

Lut2 also takes an optional bit depth parameter, bits, which defaults to the bit depth of the first input clip, and specifies the bit depth of the output clip. The user is responsible for understanding the effects of bit depth conversion, specifically from higher bit depths to lower bit depths, as no scaling or clamping is applied.

If floatout is set then the output will be floating point instead, and either lutf needs to be set or function always needs to return floating point values.

How to average 2 clips:

lut = []
for y in range(2 ** clipy.format.bits_per_sample):
   for x in range(2 ** clipx.format.bits_per_sample):
      lut.append((x + y)//2)
Lut2(clipa=clipa, clipb=clipb, lut=lut)

How to average 2 clips with a 10-bit output:

def f(x, y):
   return (x*4 + y)//2
Lut2(clipa=clipa8bit, clipb=clipb10bit, function=f, bits=10)