librosa/feature/spectral.py
def rms(y=None, S=None, frame_length=2048, hop_length=512,
        center=True, pad_mode='reflect'):
    '''Compute root-mean-square (RMS) value for each frame, either from the
    audio samples `y` or from a spectrogram `S`.

    Computing the RMS value from audio samples is faster as it doesn't require
    a STFT calculation. However, using a spectrogram will give a more accurate
    representation of energy over time because its frames can be windowed,
    thus prefer using `S` if it's already available.


    Parameters
    ----------
    y : np.ndarray [shape=(n,)] or None
        (optional) audio time series. Required if `S` is not input.

    S : np.ndarray [shape=(d, t)] or None
        (optional) spectrogram magnitude. Required if `y` is not input.

    frame_length : int > 0 [scalar]
        length of analysis frame (in samples) for energy calculation

    hop_length : int > 0 [scalar]
        hop length for STFT. See `librosa.core.stft` for details.

    center : bool
        If `True` and operating on time-domain input (`y`), pad the signal
        by `frame_length//2` on either side.

        If operating on spectrogram input, this has no effect.

    pad_mode : str
        Padding mode for centered analysis.  See `np.pad` for valid
        values.

    Returns
    -------
    rms : np.ndarray [shape=(1, t)]
        RMS value for each frame


    Examples
    --------
    >>> y, sr = librosa.load(librosa.util.example_audio_file())
    >>> librosa.feature.rms(y=y)
    array([[ 0.   ,  0.056, ...,  0.   ,  0.   ]], dtype=float32)

    Or from spectrogram input

    >>> S, phase = librosa.magphase(librosa.stft(y))
    >>> rms = librosa.feature.rms(S=S)

    >>> import matplotlib.pyplot as plt
    >>> plt.figure()
    >>> plt.subplot(2, 1, 1)
    >>> plt.semilogy(rms.T, label='RMS Energy')
    >>> plt.xticks([])
    >>> plt.xlim([0, rms.shape[-1]])
    >>> plt.legend(loc='best')
    >>> plt.subplot(2, 1, 2)
    >>> librosa.display.specshow(librosa.amplitude_to_db(S, ref=np.max),
    ...                          y_axis='log', x_axis='time')
    >>> plt.title('log Power spectrogram')
    >>> plt.tight_layout()

    Use a STFT window of constant ones and no frame centering to get consistent
    results with the RMS computed from the audio samples `y`

    >>> S = librosa.magphase(librosa.stft(y, window=np.ones, center=False))[0]
    >>> librosa.feature.rms(S=S)

    '''
    if y is not None and S is not None:
        raise ValueError('Either `y` or `S` should be input.')
    if y is not None:
        y = to_mono(y)
        if center:
            y = np.pad(y, int(frame_length // 2), mode=pad_mode)

        x = util.frame(y,
                       frame_length=frame_length,
                       hop_length=hop_length)
    elif S is not None:
        x, _ = _spectrogram(y=y, S=S,
                            n_fft=frame_length,
                            hop_length=hop_length)
    else:
        raise ValueError('Either `y` or `S` must be input.')
    return np.sqrt(np.mean(np.abs(x)**2, axis=0, keepdims=True))
def rms(y=None, S=None, frame_length=2048, hop_length=512,
        center=True, pad_mode='reflect'):
    '''Compute root-mean-square (RMS) value for each frame, either from the
    audio samples `y` or from a spectrogram `S`.

    Computing the RMS value from audio samples is faster as it doesn't require
    a STFT calculation. However, using a spectrogram will give a more accurate
    representation of energy over time because its frames can be windowed,
    thus prefer using `S` if it's already available.


    Parameters
    ----------
    y : np.ndarray [shape=(n,)] or None
        (optional) audio time series. Required if `S` is not input.

    S : np.ndarray [shape=(d, t)] or None
        (optional) spectrogram magnitude. Required if `y` is not input.

    frame_length : int > 0 [scalar]
        length of analysis frame (in samples) for energy calculation

    hop_length : int > 0 [scalar]
        hop length for STFT. See `librosa.core.stft` for details.

    center : bool
        If `True` and operating on time-domain input (`y`), pad the signal
        by `frame_length//2` on either side.

        If operating on spectrogram input, this has no effect.

    pad_mode : str
        Padding mode for centered analysis.  See `np.pad` for valid
        values.

    Returns
    -------
    rms : np.ndarray [shape=(1, t)]
        RMS value for each frame


    Examples
    --------
    >>> y, sr = librosa.load(librosa.util.example_audio_file())
    >>> librosa.feature.rms(y=y)
    array([[ 0.   ,  0.056, ...,  0.   ,  0.   ]], dtype=float32)

    Or from spectrogram input

    >>> S, phase = librosa.magphase(librosa.stft(y))
    >>> rms = librosa.feature.rms(S=S)

    >>> import matplotlib.pyplot as plt
    >>> plt.figure()
    >>> plt.subplot(2, 1, 1)
    >>> plt.semilogy(rms.T, label='RMS Energy')
    >>> plt.xticks([])
    >>> plt.xlim([0, rms.shape[-1]])
    >>> plt.legend(loc='best')
    >>> plt.subplot(2, 1, 2)
    >>> librosa.display.specshow(librosa.amplitude_to_db(S, ref=np.max),
    ...                          y_axis='log', x_axis='time')
    >>> plt.title('log Power spectrogram')
    >>> plt.tight_layout()

    Use a STFT window of constant ones and no frame centering to get consistent
    results with the RMS computed from the audio samples `y`

    >>> S = librosa.magphase(librosa.stft(y, window=np.ones, center=False))[0]
    >>> librosa.feature.rms(S=S)

    '''
    if y is not None and S is not None:
        raise ValueError('Either `y` or `S` should be input.')
    if y is not None:
        y = to_mono(y)
        if center:
            y = np.pad(y, int(frame_length // 2), mode=pad_mode)

        x = util.frame(y,
                       frame_length=frame_length,
                       hop_length=hop_length)
    elif S is not None:
        x, _ = _spectrogram(y=y, S=S,
                            n_fft=frame_length,
                            hop_length=hop_length)
    else:
        raise ValueError('Either `y` or `S` must be input.')
    return np.sqrt(np.mean(np.abs(x)**2, axis=0, keepdims=True))
Compute root-mean-square (RMS) value for each frame, either from the
    audio samples `y` or from a spectrogram `S`.

    Computing the RMS value from audio samples is faster as it doesn't require
    a STFT calculation. However, using a spectrogram will give a more accurate
    representation of energy over time because its frames can be windowed,
    thus prefer using `S` if it's already available.


    Parameters
    ----------
    y : np.ndarray [shape=(n,)] or None
        (optional) audio time series. Required if `S` is not input.

    S : np.ndarray [shape=(d, t)] or None
        (optional) spectrogram magnitude. Required if `y` is not input.

    frame_length : int > 0 [scalar]
        length of analysis frame (in samples) for energy calculation

    hop_length : int > 0 [scalar]
        hop length for STFT. See `librosa.core.stft` for details.

    center : bool
        If `True` and operating on time-domain input (`y`), pad the signal
        by `frame_length//2` on either side.

        If operating on spectrogram input, this has no effect.

    pad_mode : str
        Padding mode for centered analysis.  See `np.pad` for valid
        values.

    Returns
    -------
    rms : np.ndarray [shape=(1, t)]
        RMS value for each frame


    Examples
    --------
    >>> y, sr = librosa.load(librosa.util.example_audio_file())
    >>> librosa.feature.rms(y=y)
    array([[ 0.   ,  0.056, ...,  0.   ,  0.   ]], dtype=float32)

    Or from spectrogram input

    >>> S, phase = librosa.magphase(librosa.stft(y))
    >>> rms = librosa.feature.rms(S=S)

    >>> import matplotlib.pyplot as plt
    >>> plt.figure()
    >>> plt.subplot(2, 1, 1)
    >>> plt.semilogy(rms.T, label='RMS Energy')
    >>> plt.xticks([])
    >>> plt.xlim([0, rms.shape[-1]])
    >>> plt.legend(loc='best')
    >>> plt.subplot(2, 1, 2)
    >>> librosa.display.specshow(librosa.amplitude_to_db(S, ref=np.max),
    ...                          y_axis='log', x_axis='time')
    >>> plt.title('log Power spectrogram')
    >>> plt.tight_layout()

    Use a STFT window of constant ones and no frame centering to get consistent
    results with the RMS computed from the audio samples `y`

    >>> S = librosa.magphase(librosa.stft(y, window=np.ones, center=False))[0]
    >>> librosa.feature.rms(S=S)