Basic filters

Description

Classes for some common filter types.

Files
file	filters.h

Classes
class	signalsmith::filters::BiquadStatic< Sample, cookbookBandwidth >
	A standard biquad. More...

Enums
enum class	signalsmith::filters::BiquadDesign { BiquadDesign::bilinear , BiquadDesign::cookbook , BiquadDesign::oneSided , BiquadDesign::vicanek }
	Filter design methods. More...

Enum Details

BiquadDesign

enum class signalsmith::filters::BiquadDesign

strong

Filter design methods.

These differ mostly in how they handle frequency-warping near Nyquist:

Enumerator
bilinear	Bilinear transform, adjusting for centre frequency but not bandwidth.
cookbook	RBJ's "Audio EQ Cookbook". Based on bilinear, adjusting bandwidth (for peak/notch/bandpass) to preserve the ratio between upper/lower boundaries. This performs oddly near Nyquist.
oneSided	Based on bilinear, adjusting bandwidth to preserve the lower boundary (leaving the upper one loose).
vicanek	From Martin Vicanek's Matched Second Order Digital Filters. Falls back to oneSided for shelf and allpass filters. This takes the poles from the impulse-invariant approach, and then picks the zeros to create a better match. This means that Nyquist is not 0dB for peak/notch (or -Inf for lowpass), but it is a decent match to the analogue prototype.