allow python fallback for arbitrary low-pass filter cutoff frequencies

        N, Wn = sig.cheb2ord(fc / (fs / 2), (fc + 500) / (fs / 2), 3, 60)

        b, a = sig.cheby2(N, 60, Wn, "low")

        # Apply the Butterworth filter for each channels, across time axis

        # y = sig.lfilter(b, a, axis=0) # non zero-phase filter

        y = sig.filtfilt(b, a, x, axis=0)  # zero-phase filer, batch processing

        y = sig.filtfilt(b, a, x, axis=0)  # zero-phase filter, batch processing

    else:

        y = x

from pathlib import Path, PurePath

from shutil import copyfile

from typing import Optional, Union

from warnings import warn

from ivas_processing_scripts.audiotools import audio, audioarray, metadata

from ivas_processing_scripts.audiotools.audiofile import write

from ivas_processing_scripts.audiotools.audioarray import lpfilter

from ivas_processing_scripts.audiotools.convert.channelbased import convert_channelbased

from ivas_processing_scripts.audiotools.convert.masa import convert_masa

from ivas_processing_scripts.audiotools.convert.objectbased import convert_objectbased

    """low-pass filtering"""

    if fc is not None:

        try:

            if logger:

                logger.debug(

                    f"Applying low-pass filter with cutoff {fc}Hz using ITU STL filter"

                )

            x.audio = lpfilter_itu(x, fc)

        except NotImplementedError:

            warn(f"Low-pass filter cutoff {fc}Hz not supported by ITU filter. Falling back to python implementation.")

            if logger:

                logger.debug(f" Applying low-pass filter with cutoff {fc}Hz using python")

            x.audio = lpfilter(x.audio, fc, x.fs)

    """MNRU"""

    if mnru_q is not None:

    flt_vals = [1500, 3500, 7000, 10000, 12000, 14000, 20000]

    try:

        flt_type = flt_types[flt_vals.index(fc)]

    except Exception:

        raise ValueError(f"LP cut-off frequency {fc}Hz not supported.")

    except ValueError as e:

        raise NotImplementedError(f"LP cut-off frequency {fc}Hz not supported by ITU filter.") from e

    # resample if samplingrate is not supported

    old_fs = None