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import asyncio
import alsaaudio
import numpy as np
import scipy.signal as signal
from rtlsdr import RtlSdr
device = alsaaudio.PCM(alsaaudio.PCM_PLAYBACK, device='default')
device.setchannels(1)
device.setrate(50000)
device.setformat(alsaaudio.PCM_FORMAT_S16_LE)
device.setperiodsize(520)
async def streaming():
sdr = RtlSdr()
sdr.sample_rate = 1.2e6
sdr.center_freq = 91.8e6
prev = None
device.write(np.array([0] * 100000).astype('int16'))
async for samples in sdr.stream():
samples = np.array(samples).astype('complex64')
samples = signal.decimate(samples, int(1.2e6 / 200e3))
if prev is not None:
samples = np.insert(samples, 0, prev)
prev = samples[-1]
samples = np.angle(samples[1:] * np.conj(samples[:-1]))
x = np.exp(-1 / (200e3 * 75e-6))
samples = signal.lfilter([1-x], [1,-x], samples)
samples = signal.decimate(samples, int(200e3 / 50e3))
samples *= 10000
device.write(samples.astype('int16'))
await sdr.stop()
sdr.close()
loop = asyncio.get_event_loop()
loop.run_until_complete(streaming())
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