Super nerdy DSP content warning.
If you program audio DSP effects, you have undoubtedly heard of Robert Bristow-Johnson. If you haven’t heard of him, get yourself a copy of his Audio-EQ Cookbook. This is a succinct little document, that provides coefficient generation formulas for pretty much any second order filter building block you would ever need: lowpass, highpass, allpass, peak EQ, notch, shelving filters, etc. Today, I am implementing these formulas for my own code, but I know I’ve implemented them in at least 3 prior DSP environments. Really good stuff.
A quick Google search doesn’t turn up a ton on Robert Bristow-Johnson (or RBJ, as he is often abbreviated). He worked at Eventide, Fostex, Young Chang (Kurzweil), and Wave Mechanics. RBJ has a few AES papers as well, all of which are worth reading, covering topics ranging from PSOLA pitch shifting (made famous by AutoTune) to filter design to interpolation for oversampling.
If anyone out there knows RBJ, send him my thanks!
thanks for the ego-inflation. i don’t need it. the cookbook is a little thing. i haven’t yet been able to walk on water.
also, the PSOLA method (i would call it “Lent’s algorithm”) is not used, as far as i understand, by Autotune. but it *is* used by Pitch Doctor.
RBJ is amazing. Every DSP programmer I know (and I know several) all agree.
I remember trying out a formant-correcting/altering pitch-shifter plug-in he had done at Wave Mechanics. This would have been at AES around 1996-1997. It was absolutely amazing. Never heard one as good or as interesting since.
RBJ, I salute you!