fm_demod.py

import simpleaudio as sa
from rtlsdr import RtlSdr
import math
import signal

def signal_handler(signum, frame):
    exit(-1)
signal.signal(signal.SIGINT, signal_handler)

# User definable settings
fm_freq = 102.9e6

# Nerdy definable settings
buffer_sec = 1
run_on_gpu = True
audio_fs = 48e3

# Setup SDR stuff
sdr = RtlSdr()
sdr.set_sample_rate(2.4e6)
sdr.set_center_freq(fm_freq)

# Setup GPU
if run_on_gpu:
    import cupy as np
    import cusignal as signal
else:
    import numpy as np
    from scipy import signal

# Receiving loop
def callback(rec_signal, ctx):
    rec_signal = signal.resample_poly(rec_signal, 3, 2, window='flattop')
    rec_signal = np.diff(np.unwrap(np.angle(rec_signal)))
    caudio = signal.resample_poly(rec_signal, 1, (1.5*sdr.sample_rate)//audio_fs, window='flattop')
    caudio *= 65535/math.pi
    sa.play_buffer(np.asnumpy(caudio.astype(np.int16)), 1, 2, int(audio_fs))

sdr.read_samples_async(callback, int(sdr.sample_rate*buffer_sec))

stream.stop_stream()
pa.close()
sdr.close()