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Filters.py
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import numpy as np
from scipy.signal import freqz
class IirFilter:
def __init__(self, b=[1.0], a=[1.0]):
self.b = np.array(b)
self.a = np.array(a)
self.inputs = np.zeros(len(b))
self.outputs = np.zeros(len(a))
self.gain = 1.0
def set_gain(self, gain):
self.gain = gain
def tick(self, in_sample):
self.outputs[0] = 0.0
self.inputs[0] = in_sample * self.gain
for i in range(self.inputs.size - 1, 0, -1):
if i < self.b.size: # See note in `set_b_coefficients`.
self.outputs[0] += self.b[i] * self.inputs[i]
self.inputs[i] = self.inputs[i-1]
self.outputs[0] += self.b[0] * self.inputs[0]
for i in range(self.a.size - 1, 0, -1):
self.outputs[0] += -self.a[i] * self.outputs[i]
self.outputs[i] = self.outputs[i-1]
return self.outputs[0]
def set_b_coefficients(self, b):
# Allow growing and shrinking the b coefficients with minimal noise caused by 0s in history
# by keeping inputs as the max length of any b coefficients that have been set.
if len(b) > len(self.inputs):
self.inputs = np.concatenate([self.inputs, np.zeros(len(b) - len(self.inputs))])
self.b = np.array(b)
# Convenience method wrapping around scipy.signal.freqz
def freqz(self):
return freqz(self.b, self.a)
class OneZeroFilter:
def __init__(self, zero=-1.0):
self.in1 = self.in2 = self.out1 = 0.0
self.set_zero(zero)
def tick(self, in_sample):
self.in1 = in_sample
self.out1 = self.b1 * self.in2 + self.b0 * self.in1
self.in2 = self.in1
return self.out1
def set_zero(self, zero):
# Normalize coefficients for unity gain
self.b0 = 1.0 / (1.0 + zero) if zero > 0 else 1.0 / (1.0 - zero)
self.b1 = -zero * self.b0
# TODO could be broken
def phase_delay(self, frequency, fs=44100):
omega_t = 2 * np.pi * frequency / fs
real = 0.0
imag = 0.0
real += self.b0 * np.cos(0)
imag -= self.b0 * np.sin(0)
real += self.b1 * np.cos(omega_t)
imag += self.b1 * np.sin(omega_t)
phase = np.arctan2(imag, real)
phase = -phase % (2 * np.pi)
return phase / omega_t
def set_coefficients(self, b0, b1):
self.b0 = b0
self.b1 = b1
def clear(self):
self.in1 = self.in2 = self.out1 = 0.0
# One-pole lowpass with feedback coefficient of 0.5
class OnePoleFilter:
def __init__(self, g=0.5, p=0.5):
self.z_1 = 0 # memory for single pole lowpass filter at bridge
self.g = g
self.p = p
def tick(self, in_sample):
out_sample = self.g * in_sample + self.p * self.z_1
self.z_1 = out_sample
return out_sample
def clear(self):
self.z_1 = 0.0
class TwoZeroFilter:
def __init__(self):
self.set_coefficients()
self.in1 = 0.0
self.in2 = 0.0
def tick(self, in_sample):
out_sample = self.b2 * self.in2 + self.b1 * self.in1 + self.b0 * in_sample
self.in2 = self.in1
self.in1 = in_sample
return out_sample
def set_coefficients(self, b0=1.0, b1=0.0, b2=0.0):
self.b0 = b0
self.b1 = b1
self.b2 = b2
def get_coefficients(self):
return [self.b0, self.b1, self.b2]
def clear(self):
self.in1 = 0.0
self.in2 = 0.0
class PoleZeroFilter():
def __init__(self, b0=1.0, b1=0.0, a1=1.0):
self.set_coefficients(b0, b1, a1)
self.out1 = 0.0
self.in1 = 0.0
def tick(self, in_sample):
out_sample = self.b0 * in_sample + self.b1 * self.in1 - self.a1 * self.out1
self.in1 = in_sample
self.out1 = out_sample
return out_sample
def set_coefficients(self, b0=1.0, b1=0.0, a1=1.0):
self.b0 = b0
self.b1 = b1
self.a1 = a1
def set_block_zero(self, pole=0.99):
self.b0 = 1.0
self.b1 = -1.0
self.a1 = -pole
def clear(self):
self.in1 = 0.0
self.out1 = 0.0
class NoOpFilter:
def tick(self, in_sample):
return in_sample
def clear(self):
return self