Programmer Guide/SPU Reference/LPSPECTRUM: Difference between revisions
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This function computes the LPC<nowiki>-</nowiki>smoothed spectrum of the speech signal X. First the inverse filter coefficients are computed using the same method (differentiation and auto-correlation method) as in <code>[[Programmer Guide/SPU Reference/LPCOEFS - linear prediction coefs.|LPCOEFS]]</code> and than the frequency response (amplitudes) for this filter is computed using an FFT. The signal vector <var>x</var> must be windowed before being connected to this atom. Optional pre-filtering (differentiation, if <var>d</var><code>>0</code>) is applied to the signal before the coefficients' iteration. The spectrum computed using this method can be interpreted as the transfer function of the human vocal tract and is mainly used for speech formant (candidate) extraction. | This function computes the LPC<nowiki>-</nowiki>smoothed spectrum of the speech signal X. First the inverse filter coefficients are computed using the same method (differentiation and auto-correlation method) as in <code>[[Programmer Guide/SPU Reference/LPCOEFS - linear prediction coefs.|LPCOEFS]]</code> and than the frequency response (amplitudes) for this filter is computed using an FFT. The signal vector <var>x</var> must be windowed before being connected to this atom. Optional pre-filtering (differentiation, if <var>d</var><code>>0</code>) is applied to the signal before the coefficients' iteration. The spectrum computed using this method can be interpreted as the transfer function of the human vocal tract and is mainly used for speech formant (candidate) extraction. | ||
Type of output spectrum selected by input <var>typ</var>{| | Type of output spectrum selected by input <var>typ</var> | ||
{| | |||
|- | |- | ||
|value of <var>typ</var> | |value of <var>typ</var> | ||
Latest revision as of 11:48, 3 May 2018
LPSPECTRUM - LP smoothed spectrum
Usage:
LPSPECTRUM x n d typ c lfft
Inputs:
| x | signal vector (nx samples) | no default |
| n | number of coefficients | def.=20
|
| d | pre-emphasis (differentiation factor, 0..1) | def.=1
|
| typ | selects the type of output spectrum | def.=LOGARITHMIC
|
| c | spectrum scale factor or offset | def.=1(linear) or 0(dB)
|
| lfft | fft length for spectrum computation | def.=2M>=nx |
Outputs:
| y | LPC-smoothed spectrum (vocal tract transfer function, lfft/2+1 samples) |
| alpha | error energy |
Function:
This function computes the LPC-smoothed spectrum of the speech signal X. First the inverse filter coefficients are computed using the same method (differentiation and auto-correlation method) as in LPCOEFS and than the frequency response (amplitudes) for this filter is computed using an FFT. The signal vector x must be windowed before being connected to this atom. Optional pre-filtering (differentiation, if d>0) is applied to the signal before the coefficients' iteration. The spectrum computed using this method can be interpreted as the transfer function of the human vocal tract and is mainly used for speech formant (candidate) extraction.
Type of output spectrum selected by input typ
| value of typ | type of spectrum stored in y | usage of c |
0 or POWER
|
power spectrum | scaling factor |
1 or LINEAR
|
amplitude spectrum | scaling factor |
2 or LOGARITHMIC
|
logarithmic amplitude spectrum | offset in dB |
