lpf.py

from audiolazy import sHz, sinusoid, Stream, AudioIO, z, pi, chunks
import time, sys

# Basic initialization
rate = 44100
s, Hz = sHz(rate)

# Some time-variant coefficients
cycle_a1 = [.1, .2, .1, 0, -.1, -.2, -.1, 0]
cycle_a2 = [.1, 0, -.1, 0, 0]
a1 = Stream(*cycle_a1)
a2 = Stream(*cycle_a2) * 2
b1 = sinusoid(18 * Hz) # Sine phase
b2 = sinusoid(freq=7 * Hz, phase=pi/2) # Cosine phase

# The filter
filt = (1 + b1 * z ** -1 + b2 * z ** -2 + .7 * z ** -5)
filt /= (1 - a1 * z ** -1 - a2 * z ** -2 - .1 * z ** -3)

# A really simple input
input_data = sinusoid(220 * Hz)

# Let's play it!
api = sys.argv[1] if sys.argv[1:] else None # Choose API via command-line
chunks.size = 1 if api == "jack" else 16
with AudioIO(api=api) as player:
  th = player.play(input_data, rate=rate)
  time.sleep(1) # Wait a sec
  th.stop()
  time.sleep(1) # One sec "paused"
  player.play(filt(input_data), rate=rate) # It's nice with rate/2 here =)
  time.sleep(3) # Play the "filtered" input (3 secs)