36 lines
854 B
Nim
36 lines
854 B
Nim
|
## One-pole LPF for smooth parameter changes
|
||
|
|
##
|
||
|
|
## https://www.musicdsp.org/en/latest/Filters/257-1-pole-lpf-for-smooth-parameter-changes.html
|
||
|
|
|
||
|
|
import math
|
||
|
|
|
||
|
|
const TwoPi = PI * 2
|
||
|
|
|
||
|
|
type
|
||
|
|
ParamSmooth* = object
|
||
|
|
a, b, t, z: float
|
||
|
|
fs: float64
|
||
|
|
|
||
|
|
|
||
|
|
proc reset*(self: var ParamSmooth) =
|
||
|
|
self.z = 0.0
|
||
|
|
|
||
|
|
|
||
|
|
proc setSampleRate*(self: var ParamSmooth, sampleRate: float64) =
|
||
|
|
if sampleRate != self.fs:
|
||
|
|
self.fs = sampleRate
|
||
|
|
self.a = exp(-TwoPi / (self.t * 0.001 * sampleRate))
|
||
|
|
self.b = 1.0 - self.a
|
||
|
|
self.z = 0.0
|
||
|
|
|
||
|
|
|
||
|
|
proc process*(self: var ParamSmooth, sample: float): float =
|
||
|
|
self.z = (sample * self.b) + (self.z * self.a)
|
||
|
|
return self.z
|
||
|
|
|
||
|
|
|
||
|
|
proc initParamSmooth*(smoothingTimeMs: float = 20.0, sampleRate: float64 = 48_000.0): ParamSmooth =
|
||
|
|
result.t = smoothingTimeMs
|
||
|
|
result.setSampleRate(sampleRate)
|
||
|
|
|