lofi.h

Word-length reduction. bits may be fractional -- 3.5 bits is a perfectly good step size, and sweeping the control through integers only would step. At 24 bits the step is below float's own resolution and this is transparent.

Sample-rate reduction by sample-and-hold, to any rate, including one that does not divide the host's. A phase accumulator decides when to take a new sample, so 11.025 kHz inside 48 kHz holds for 4.35 samples on average rather than snapping to 4 or 5 and sounding like a different rate.

Triangle wavefolding: what goes past +/-1 is reflected back, as many times as it takes. Pushing a sine into it adds harmonics that a clipper cannot -- a clipper flattens the top of the wave, a folder puts a new wave on it -- and the timbre keeps changing with drive long after a clipper has become a square.

fold() is the closed form of "reflect until inside": the input mapped onto a triangle wave of period 4, which is one fmod and one abs per sample instead of a loop that runs longer the harder it is driven.

bias shifts the input before folding. A symmetric fold makes odd harmonics only; a little bias breaks the symmetry and lets the even ones in.

Any per-sample shaper, run at 2^Stages times the rate.

The wrapper owns the shaper (reach it through shaper() to set its controls) and the half-band cascade from resample.h. The shaper must be a plain float process(float); its own state, if any, advances at the OVERSAMPLED rate, which is right for a memoryless shape and something to know about for one with a time constant.

latencySamples() is the cascade's delay at the base rate, an integer by construction (see resample.h for why 32x is the ceiling), and it is the number the plugin must report. The IIR flavour has none, at the cost of phase linearity -- OversampledIir<> for when a parallel path does not need to null.