salvus.data.processing.trace_processing

def zerophase_chebychev_lowpass_filter(
    trace: obspy.Trace, freqmax: float
) -> None: ...

Custom Chebychev type two zerophase lowpass filter useful for decimation filtering.

This filter is stable up to a reduction in frequency with a factor of 10. If more reduction is desired, simply decimate in steps.

This has proven to work well in the past.