spectral.py 文件源码

def mel_spectrum(power_spectrum: np.ndarray,
                 mel_fbank: np.ndarray = None,
                 fs: int = None,
                 window_width: int = None,
                 n_filt: int = 40) -> np.ndarray:
    """
    Computes a Mel spectrogram from the specified power spectrogram.

    Optionally, precomputed Mel filter banks can be passed to this function, in which case the n_filt, fs, and 
    window_width parameters are ignored. If precomputed Mel filter banks are used, the caller has to ensure that they
    have correct shape.

    Parameters
    ----------
    power_spectrum: numpy.ndarray
        The power spectrogram from which a Mel spectrogram should be computed
    mel_fbank: numpy.ndarray, optional
        Precomputed Mel filter banks
    fs: int
        Sampling frequency of the signal from which the power spectrogram was computed. Ignored if precomputed Mel
        filter banks are used.
    window_width: int
        Window width in samples that was used to comput the power spectrogram. Ignored if precomputed Mel filter banks 
        are used.
    n_filt: int
        Number of Mel filter banks to use. Ignored if precomputed Mel filter banks are used.

    Returns
    -------
    numpy.ndarray
        Mel spectrogram computed from the specified power spectrogram
    """
    if mel_fbank is None:
        _, mel_fbank = mel_filter_bank(fs, window_width, n_filt)

    filter_banks = np.dot(mel_fbank, power_spectrum)

    return filter_banks