All credit to:
Su, Wei, "Decomposition of High-Order FIR Filters and Minimum-Phase Filter Design. " Master's Thesis, University of Tennessee, 2002. https://trace.tennessee.edu/utk_gradthes/2177
This repository contains the c++ code copied out of Wei's thesis document for the decomposition of an FIR filter, as well as an incomplete Python implementation of the same code (thus far, I've only implemented the part I needed, which is decomposition of FIR filters that will certainly be larger than 2nd order, so I skipped some of the initial time saving checks. I may come back and make the more faithful implementation at some point, but the code is here in the meantime in case anyone finds it useful.)