.\" Copyright (c) 1987 Entropic Speech, Inc.; All rights reserved.\ @(#)cepstrum.3	1.2 21 Jun 1988 ESI.TH CEPSTRUM 3\-ESPSsp 21 Jun 1988.ds ]W "\fI\s+4\ze\h'0.05'e\s-4\v'-0.4m'\fP\(*p\v'0.4m'\ Entropic Speech, Inc..SH NAMEafc2cep \- transform autoregressive filter coefficients into cepstrum coefficients.PPcep2afc \- transform cepstrum coefficients into autoregressive filter coefficients.SH SYNOPSIS.ft B.brint .brafc2cep (afc, cep, order).brint order;.brfloat *afc,*cep;.sp.PP.ft B.brint.brcep2afc (cep, afc, order).brint size;.brfloat *afc,*cep;.SH DESCRIPTIONEach function transforms a set of coefficients that contain spectralinformation into an equivalent set of coefficients. .PP.I Afc2ceptransforms the input autoregressive filter coefficients (\fIafc\fR) into the cepstrum coefficients (\fIcep\fR).\fIOrder\fR is the number of inputand output parameters. .PP.I Cep2afctransforms the \fIcep\fRs into\fIafc\fRs.\fIOrder\fR is the number of input and output parameters..SH WARNINGS.PPThe first cepstral coefficient = ln{sqrt[residual power]} is not returned in the cep[] array by \fIafc2cep\fR, nor is it passed into \fIcep2afc\fR. The first autregressivefilter coefficient (= 1) is neither passed into \fIafc2cep\fRnor returned by \fIcep2afc\fR..SH DIAGNOSTICS.PPNone..SH EXAMPLES.nf    /*     * Convert afc to cep    */	int size = 3;	static float afc[] = {.9, .5, .1};	float cep[3];	/* Ready to Convert */	(void)afc2cep(afc, cep, size);		.		.		.    /*     * Convert back to afc    */	(void)cep2afc(cep, afc, size);.fi.SH BUGSNone known..SH SEE ALSO.PPrc_reps(3-ESPSsp), spectrans(1-ESPS), transpec(1-ESPS).SH AUTHORManual page and code by David Burton