librosa.filters._multirate_fb¶

librosa.filters._multirate_fb(center_freqs=None, sample_rates=None, Q=25.0, passband_ripple=1, stopband_attenuation=50, ftype=’ellip’)[source]¶

Helper function to construct a multirate filterbank.

A filter bank consists of multiple band-pass filters which divide the input signal into subbands. In the case of a multirate filter bank, the band-pass filters operate with resampled versions of the input signal, e.g. to keep the length of a filter constant while shifting its center frequency.

This implementation uses scipy.signal.iirdesign to design the filters.

Parameters:	center_freqs : np.ndarray [shape=(n,), dtype=float] Center frequencies of the filter kernels. Also defines the number of filters in the filterbank. sample_rates : np.ndarray [shape=(n,), dtype=float] Samplerate for each filter (used for multirate filterbank). Q : float Q factor (influences the filter bandwith). passband_ripple : float The maximum loss in the passband (dB) See `scipy.signal.iirdesign` for details. stopband_attenuation : float The minimum attenuation in the stopband (dB) See `scipy.signal.iirdesign` for details. ftype : str The type of IIR filter to design See `scipy.signal.iirdesign` for details.
Returns:	filterbank : list [shape=(n,), dtype=float] Each list entry comprises the filter coefficients for a single filter. sample_rates : np.ndarray [shape=(n,), dtype=float] Samplerate for each filter.
Raises:	ParameterError If center_freqs is None. If sample_rates is None. If center_freqs.shape does not match sample_rates.shape.