cepstrum.3

speech signal process tools

.\" 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 NAME
afc2cep \- transform autoregressive filter coefficients into cepstrum coefficients
.PP
cep2afc \- transform cepstrum coefficients into autoregressive filter coefficients
.SH SYNOPSIS
.ft B
.br
int 
.br
afc2cep (afc, cep, order)
.br
int order;
.br
float *afc,*cep;
.sp
.PP
.ft B
.br
int
.br
cep2afc (cep, afc, order)
.br
int size;
.br
float *afc,*cep;
.SH DESCRIPTION
Each function transforms a set of coefficients that contain spectral
information into an equivalent set of coefficients. 
.PP
.I Afc2cep
transforms the input autoregressive filter coefficients (\fIafc\fR) 
into the cepstrum coefficients (\fIcep\fR).
\fIOrder\fR is the number of input
and output parameters. 
.PP
.I Cep2afc
transforms the \fIcep\fRs into
\fIafc\fRs.
\fIOrder\fR is the number of input and output parameters.
.SH WARNINGS
.PP
The 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 autregressive
filter coefficient (= 1) is neither passed into \fIafc2cep\fR
nor returned by \fIcep2afc\fR.
.SH DIAGNOSTICS
.PP
None.
.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 BUGS
None known.
.SH SEE ALSO
.PP
rc_reps(3-ESPSsp), spectrans(1-ESPS), transpec(1-ESPS)
.SH AUTHOR
Manual page and code by David Burton