audiosr/lowpass.py

from scipy.signal import butter, lfilter
import torch
from scipy import signal
import librosa
import numpy as np

from scipy.signal import sosfiltfilt
from scipy.signal import butter, cheby1, cheby2, ellip, bessel
from scipy.signal import resample_poly


def align_length(x=None, y=None, Lx=None):
    """align the length of y to that of x

    Args:
        x (np.array): reference signal
        y (np.array): the signal needs to be length aligned

    Return:
        yy (np.array): signal with the same length as x
    """
    assert y is not None

    if Lx is None:
        Lx = len(x)
    Ly = len(y)

    if Lx == Ly:
        return y
    elif Lx > Ly:
        # pad y with zeros
        return np.pad(y, (0, Lx - Ly), mode="constant")
    else:
        # cut y
        return y[:Lx]


def bandpass_filter(x, lowcut, highcut, fs, order, ftype):
    """process input signal x using bandpass filter

    Args:
        x (np.array): input signal
        lowcut (float): low cutoff frequency
        highcut (float): high cutoff frequency
        order (int): the order of filter
        ftype (string): type of filter
            ['butter', 'cheby1', 'cheby2', 'ellip', 'bessel']

    Return:
        y (np.array): filtered signal
    """
    nyq = 0.5 * fs
    lo = lowcut / nyq
    hi = highcut / nyq

    if ftype == "butter":
        # b, a = butter(order, [lo, hi], btype='band')
        sos = butter(order, [lo, hi], btype="band", output="sos")
    elif ftype == "cheby1":
        sos = cheby1(order, 0.1, [lo, hi], btype="band", output="sos")
    elif ftype == "cheby2":
        sos = cheby2(order, 60, [lo, hi], btype="band", output="sos")
    elif ftype == "ellip":
        sos = ellip(order, 0.1, 60, [lo, hi], btype="band", output="sos")
    elif ftype == "bessel":
        sos = bessel(order, [lo, hi], btype="band", output="sos")
    else:
        raise Exception(f"The bandpass filter {ftype} is not supported!")

    # y = lfilter(b, a, x)
    y = sosfiltfilt(sos, x)

    if len(y) != len(x):
        y = align_length(x, y)
    return y


def lowpass_filter(x, highcut, fs, order, ftype):
    """process input signal x using lowpass filter

    Args:
        x (np.array): input signal
        highcut (float): high cutoff frequency
        order (int): the order of filter
        ftype (string): type of filter
            ['butter', 'cheby1', 'cheby2', 'ellip', 'bessel']

    Return:
        y (np.array): filtered signal
    """
    nyq = 0.5 * fs
    hi = highcut / nyq

    if ftype == "butter":
        sos = butter(order, hi, btype="low", output="sos")
    elif ftype == "cheby1":
        sos = cheby1(order, 0.1, hi, btype="low", output="sos")
    elif ftype == "cheby2":
        sos = cheby2(order, 60, hi, btype="low", output="sos")
    elif ftype == "ellip":
        sos = ellip(order, 0.1, 60, hi, btype="low", output="sos")
    elif ftype == "bessel":
        sos = bessel(order, hi, btype="low", output="sos")
    else:
        raise Exception(f"The lowpass filter {ftype} is not supported!")

    y = sosfiltfilt(sos, x)

    if len(y) != len(x):
        y = align_length(x, y)

    y_len = len(y)

    y = stft_hard_lowpass(y, hi, fs_ori=fs)

    y = sosfiltfilt(sos, y)

    if len(y) != y_len:
        y = align_length(y=y, Lx=y_len)

    return y


def stft_hard_lowpass(data, lowpass_ratio, fs_ori=44100):
    fs_down = int(lowpass_ratio * fs_ori)
    # downsample to the low sampling rate
    y = resample_poly(data, fs_down, fs_ori)

    # upsample to the original sampling rate
    y = resample_poly(y, fs_ori, fs_down)

    if len(y) != len(data):
        y = align_length(data, y)
    return y


def limit(integer, high, low):
    if integer > high:
        return high
    elif integer < low:
        return low
    else:
        return int(integer)


def lowpass(data, highcut, fs, order=5, _type="butter"):
    """
    :param data: np.float32 type 1d time numpy array, (samples,) , can not be (samples, 1) !!!!!!!!!!!!
    :param highcut: cutoff frequency
    :param fs: sample rate of the original data
    :param order: order of the filter
    :return: filtered data, (samples,)
    """

    if len(list(data.shape)) != 1:
        raise ValueError(
            "Error (chebyshev_lowpass_filter): Data "
            + str(data.shape)
            + " should be type 1d time array, (samples,) , can not be (samples, 1)"
        )

    if _type in "butter":
        order = limit(order, high=10, low=2)
        return lowpass_filter(
            x=data, highcut=int(highcut), fs=fs, order=order, ftype="butter"
        )
    elif _type in "cheby1":
        order = limit(order, high=10, low=2)
        return lowpass_filter(
            x=data, highcut=int(highcut), fs=fs, order=order, ftype="cheby1"
        )
    elif _type in "ellip":
        order = limit(order, high=10, low=2)
        return lowpass_filter(
            x=data, highcut=int(highcut), fs=fs, order=order, ftype="ellip"
        )
    elif _type in "bessel":
        order = limit(order, high=10, low=2)
        return lowpass_filter(
            x=data, highcut=int(highcut), fs=fs, order=order, ftype="bessel"
        )
    # elif(_type in "stft"):
    #     return stft_hard_lowpass(data, lowpass_ratio=highcut / int(fs / 2))
    # elif(_type in "stft_hard"):
    #     return stft_hard_lowpass_v0(data, lowpass_ratio=highcut / int(fs / 2))
    else:
        raise ValueError("Error: Unexpected filter type " + _type)


def bandpass(data, lowcut, highcut, fs, order=5, _type="butter"):
    """
    :param data: np.float32 type 1d time numpy array, (samples,) , can not be (samples, 1) !!!!!!!!!!!!
    :param lowcut: low cutoff frequency
    :param highcut: high cutoff frequency
    :param fs: sample rate of the original data
    :param order: order of the filter
    :param _type: type of filter
    :return: filtered data, (samples,)
    """
    if len(list(data.shape)) != 1:
        raise ValueError(
            "Error (chebyshev_lowpass_filter): Data "
            + str(data.shape)
            + " should be type 1d time array, (samples,) , can not be (samples, 1)"
        )
    if _type in "butter":
        order = limit(order, high=10, low=2)
        return bandpass_filter(
            x=data,
            lowcut=int(lowcut),
            highcut=int(highcut),
            fs=fs,
            order=order,
            ftype="butter",
        )
    elif _type in "cheby1":
        order = limit(order, high=10, low=2)
        return bandpass_filter(
            x=data,
            lowcut=int(lowcut),
            highcut=int(highcut),
            fs=fs,
            order=order,
            ftype="cheby1",
        )
    # elif(_type in "cheby2"):
    #     return bandpass_filter(x=data,lowcut=int(lowcut),highcut=int(highcut), fs=fs, order=order,ftype="cheby2")
    elif _type in "ellip":
        order = limit(order, high=10, low=2)
        return bandpass_filter(
            x=data,
            lowcut=int(lowcut),
            highcut=int(highcut),
            fs=fs,
            order=order,
            ftype="ellip",
        )
    elif _type in "bessel":
        order = limit(order, high=10, low=2)
        return bandpass_filter(
            x=data,
            lowcut=int(lowcut),
            highcut=int(highcut),
            fs=fs,
            order=order,
            ftype="bessel",
        )
    else:
        raise ValueError("Error: Unexpected filter type " + _type)