openwebrx-clone/csdr/chain/demodulator.py
2021-07-19 19:48:18 +02:00

57 lines
1.8 KiB
Python

from csdr.chain import Chain
from pycsdr.modules import Shift, FirDecimate, Bandpass, Squelch, FractionalDecimator
from abc import ABCMeta, abstractmethod
class Demodulator(Chain, metaclass=ABCMeta):
@abstractmethod
def setLastDecimation(self, decimation: Chain):
pass
class DemodulatorChain(Chain):
def __init__(self, samp_rate: int, audioRate: int, shiftRate: float, demodulator: Demodulator):
self.shift = Shift(shiftRate)
decimation, fraction = self._getDecimation(samp_rate, audioRate)
if_samp_rate = samp_rate / decimation
transition = 0.15 * (if_samp_rate / float(samp_rate))
self.decimation = FirDecimate(decimation, transition)
bp_transition = 320.0 / if_samp_rate
self.bandpass = Bandpass(transition=bp_transition, use_fft=True)
self.squelch = Squelch(5)
if fraction != 1.0:
demodulator.setLastDecimation(Chain(FractionalDecimator(fraction)))
workers = [
self.shift,
self.decimation,
self.bandpass,
self.squelch,
demodulator
]
super().__init__(*workers)
def setShiftRate(self, rate: float):
self.shift.setRate(rate)
def setSquelchLevel(self, level: float):
self.squelch.setSquelchLevel(level)
def setBandpass(self, low_cut: float, high_cut: float):
self.bandpass.setBandpass(low_cut, high_cut)
def _getDecimation(self, input_rate, output_rate):
if output_rate <= 0:
raise ValueError("invalid output rate: {rate}".format(rate=output_rate))
decimation = 1
target_rate = output_rate
while input_rate / (decimation + 1) >= target_rate:
decimation += 1
fraction = float(input_rate / decimation) / output_rate
return decimation, fraction