this line is misleading - it seems to be a single interrogation window ncc

[alexlib]

https://github.com/localdevices/ffpiv/blob/e25d5cc8d50fcc58faccedda2717024c348d8307/ffpiv/pnp.py#L28C55-L28C93

[hcwinsemius]

It is not. input is a w, y, x sized array as in the docstring. See tests/test_fft.py::ncc to see it at work.