features_online.py 文件源码

def _lpc(x,order):
    """Linear predictor coefficients. Supports 1D and 2D arrays only through
    iteration."""

    x = np.asarray(x)
    if x.ndim == 1:
        m = x.size
        X = fft(x,n=nextpow2(m))  # TODO nextpower of 2
        R = np.real(ifft(np.abs(X)**2)) # Auto-correlation matrix
        R = R/m
        a = _levinson(r=R, order=order)[0]
        a = np.hstack((1., a))
    elif x.ndim == 2:
        m,n = x.shape

        X = fft(x,n=nextpow2(m), axis=0) 
        R = np.real(ifft(np.abs(X)**2, axis=0)) # Auto-correlation matrix
        R = R/m
        a = np.ones((order+1,n))
        for col in range(n):
            a[1:,col] = _levinson(r=R[:,col], order=order)[0]
    else:
        raise ValueError('Supported for 1-D or 2-D arrays only.')

    return a