filterer.py

import numpy as np
import scipy.signal as ss

tau = 2 * np.pi

# Filter coefficients from
#
# cs = ss.iirfilter(1, (990, 1010), btype='bandpass', output='sos', fs=48000)
#
# Filter coefficient order is b0, b1, b2, a0, a1, a0. Filter
# sections must be normalized (a0 = 1).
cs = np.array(
    [[
        1.30728645e-03,
        0.00000000e+00,
        -1.30728645e-03,
        1.00000000e+00,
        -1.98029921e+00,
        9.97385427e-01,
    ]],
    dtype = np.float64,
)

state = np.zeros((1, 2))
nchunk = 100
nsamples = 10_000
for base in range(0, nsamples, chunk):
    t0 = base / nsamples
    t1 = (base + nchunk) / nsamples
    t = np.linspace(t0, t1, endpoint=False, dtype=np.float64)
    # https://en.wikipedia.org/wiki/Chirp#Linear
    x = np.sin(0.5 * 0.5 * nsamples * tau * t * t)
    y, state = ss.sosfilt(cs, x, zi=state)
    # now do some processing on y

Please ignore paper-bag bugs in previous revision.