spafe.utils.cepstral¶
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spafe.utils.cepstral.
cep2spec
(cep, ncep, nfreq, dct_type=2)[source]¶ Reverse the cepstrum to recover a spectrum.
Parameters: - cep (array) – cepstral data to convert to spectral data.
- ncep (int) – number of cepstrals.
- nfreq (int) – number of points to reconstruct in spectrum.
- dct_type (int) – the discrete cosine transform type. Default is 2.
- Returns
- 2d-array spec, spectrum matrix 2d-array idctm, the IDCT matrix that spec was multiplied by to give cep.
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spafe.utils.cepstral.
cmn
(x)[source]¶ Mean normalization.
Parameters: x (array) – input data. Returns: array with the mean normalized data.
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spafe.utils.cepstral.
cms
(x)[source]¶ Mean Substraction: Centering
Parameters: x (array) – input data. Returns: array with the centered data.
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spafe.utils.cepstral.
cmvn
(x)[source]¶ Mean Variance Normalisation
Parameters: x (array) – input data. Returns: array with the mean and variance normalized data.
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spafe.utils.cepstral.
cvn
(x)[source]¶ Variance Normalisation: Standardization
Parameters: x (array) – input data. Returns: array with the variance normalized data.
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spafe.utils.cepstral.
deltas
(x, w=9)[source]¶ Calculate the deltas (derivatives) of an input sequence with a W-points window (W odd, default 9) using a simple linear slope. This mirrors the delta calculation performed in feacalc etc. Each row of X is filtered separately.
Parameters: - x (array) – input sequence
- w (int) – window size to use in the derivatives calculation. Default is 9.
Returns: 2d-arrays containing the derivatives values.
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spafe.utils.cepstral.
lifter_ceps
(cepstra, L=22)[source]¶ Apply a cepstral lifter the the matrix of cepstra. This has the effect of increasing the magnitude of the high frequency DCT coeffs.
Parameters: - cepstra (np.array) – the matrix of mel-cepstra, will be numframes * numcep in size.
- L (int) – the liftering coefficient to use. Default is 22. L <= 0 disables lifter.
Returns: liftered cepstra.
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spafe.utils.cepstral.
spec2cep
(spec, ncep=9, dct_type=2)[source]¶ Calculate cepstra from spectral samples (in columns of spec).
Parameters: - spec (array) – spectral data to convert to cepstral.
- ncep (int) – number of cepstrals. Default is 9.
- dct_type (int) – the discrete cosine transform type. Default is 2.
- Returns
- 2d-array ncep, cepstral rows 2d-array dctm, the DCT matrix that spec was multiplied by to give cep.