generic.py 文件源码

def inv_preemphasis(x, coef=0.97):
    """Inverse operation of pre-emphasis

    Args:
        x (1d-array): Input signal.
        coef (float): Pre-emphasis coefficient.

    Returns:
        array: Output filtered signal.

    See also:
        :func:`preemphasis`

    Examples:
        >>> from nnmnkwii.util import example_audio_file
        >>> from scipy.io import wavfile
        >>> fs, x = wavfile.read(example_audio_file())
        >>> x = x.astype(np.float64)
        >>> from nnmnkwii import preprocessing as P
        >>> x_hat = P.inv_preemphasis(P.preemphasis(x, coef=0.97), coef=0.97)
        >>> assert np.allclose(x, x_hat)
    """
    b = np.array([1.], x.dtype)
    a = np.array([1., -coef], x.dtype)
    return signal.lfilter(b, a, x)