stream.py 文件源码

def _analog_filter(self,
                       ftype,
                       highpass=None,
                       lowpass=None,
                       order=3,
                       zerophase=True):
        ' Use a classic analog filter on the data, currently butter or bessel'
        from scipy.signal import butter, bessel
        filter_types = {'butter': butter, 'bessel': bessel}
        afilter = filter_types[ftype]
        if highpass is None and lowpass is not None:
            b, a = afilter(order, lowpass / (self.sr / 2), btype='lowpass')
        elif highpass is not None and lowpass is None:
            b, a = afilter(order, highpass / (self.sr / 2), btype='highpass')
        elif highpass is not None and lowpass is not None:
            if highpass < lowpass:
                b, a = afilter(order,
                               (highpass / (self.sr / 2),
                                lowpass / (self.sr / 2)),
                               btype='bandpass')
            else:
                b, a = afilter(order,
                               (lowpass / (self.sr / 2),
                                highpass / (self.sr / 2)),
                               btype='bandstop')
        if zerophase:
            return self.filtfilt(b, a)
        else:
            return self.lfilter(b, a)