as a hands on learner in pursuit of figuring out how stuff, works one great method is to look at older stuff. looking at this older version of the core ladder filter is pleasantly baking my noodle in this regard
first thing that jumped out was it seems to be a 4 pole with 3x oversampling, not 3 pole with 4x as the macro info states. lol.
also the decision to oversample a saturating filter while only passing though the unsaturated signal to the subsequent stages seems a bit silly unless it was necessary for some reason
but the true head scratcher and thing i'm most interested to discuss is the method of oversampling itself. instead of a polyphase filter it elects for linear interpolation?
but the only thing i can point to that seems obviously wrong is the lack of any kind of decimation filter (not pictured: doesn't exist)
aside from all that though, it points to something about the method of oversampling filters employed today that i have always found confusing: the chaining of OBC elements between stages
i get that that z-1 elements need to share state for oversampling to work properly, but how does that work when, say for four stages, there are four chained "write" elements all being clocked at sample rate. which "state" is being passed though the obc chain? do they fight over it? take turns??? hopefully someone knows, to me it simply makes no sense