I was reading this paper on optical flow, which as apart of the algorithm makes use Walsh-Hadamard transform on image patches of size 2r+1. So far, where ever I have looked, I could only find that WHTs require matrices of orders of powers of 2. In a footnote, they have mentioned splitting the patches in the middle for this purpose into sizes of r and r+1 which is something that I don't understand.
here, is a link to that paper: https://arxiv.org/pdf/1703.02563.pdf
