rctrnfrm.3

speech signal process tools

.\" Copyright (c) 1986-1990 Entropic Speech, Inc.
.\" Copyright (c) 1991 Entropic Research Laboratory, Inc. All rights reserved.
.\" @(#)rctrnfrm.3	1.8 01 May 1997 ESI/ERL
.ds ]W (c) 1991 Entropic Research Laboratory, Inc.
.TH RC_TRNFRM 3\-ESPSsp 01 May 1997
.SH NAME

rc_reps \- transform reflection coefficients into other spectral parameter sets
.br
reps_rc \- transform spectral parameter sets into reflection coefficients
.SH SYNOPSIS
.ft B
#include <esps/anafea.h>
.sp
.br
int 
.br
rc_reps(rc, output, output_type, size, bwidth, frq_res)
.br
int size, output_type;
.br
float *rc, *output, bwidth, frq_res;
.sp
.br
int
.br
reps_rc(input, input_type, rc, size, bwidth)
.br
int size, input_type;
.br
float *input, *rc, bwidth;
.SH DESCRIPTION
Each function transforms a set of coefficients that contain spectral
information into another equivalent set of coefficients. 
Valid spectral types are defined in \fIanafea.h\fR under \fIspec_reps[]\fR, 
but they include
reflection coefficients (RC), log area ratios (LAR), normalized
autocorrelations (AUTO), autoregressive filter coefficients (AFC),
cepstrum coefficients (CEP), and line spectral frequencies (LSF).
\fIrc_reps\fR starts with RCs and 
converts them into LARs, AFCs, AUTOs, CEPs, or LSFs; 
\fIreps_rc\fR transforms LARs, AFCs, AUTOs, CEPs, or
LSFs into RCs.
.PP
.I rc_reps
transforms the input \fIrc\fRs into the parameter type \fIoutput_type\fR
and returns them in \fIoutput\fR. \fISize\fR is the number of input
and output parameters. \fIBwidth\fR and \fIfrq_res\fR are parameters
that are only used when transforming to LSFs. \fIBwidth\fR should
equal the bandwidth (Nyquist frequency) 
of the data that was used in estimating the RCs.
\fIFrq_res\fR specifies the resolution of the search grid that
is used in finding the LSFs.
For signal bandwidths of 4000 Hz., \fIfrq_res\fR between 2 and 50 Hz.
are reasonable.
.PP
.I reps_rc
transforms the \fIinput\fR from \fIinput_type\fR parameters into
RCs and returns them in \fIrc\fR.
\fISize\fR is the number of input and output parameters.
\fIBwidth\fR is the Nyquist frequency of the source sampled data
and is only used when converting from LSFs.
.SH WARNINGS
.PP
The leading \-1 for AFCs and the leading 1 for normalized AUTOs
are not included in the input or output vectors.
Neither is the first term = ln{sqrt[residual power]} for CEPs.
.SH DIAGNOSTICS
.PP
Both functions return 0 for normal completion, and they return \-1 if
they encounter invalid spectral types.
If input and output parameters are both RCs, a warning is issued,
but RCs are returned in the output array.
.SH EXAMPLES
.nf
    /*
     * Convert RCs to LARs
     */
	#include <esps/anafea.h>
	int size = 3, output_type = LAR, input_type = LAR;
	static float rc[] = {.9, .5, .1};
	float lar[3], bwidth, frq_res;

	/* Ready to Convert */

	if((rc_reps(rc, lar, output_type, size, bwidth, frq_res)) == \-1) {
	    TROUBLE WITH CONVERSION
	}


    /*
     * Convert back to RCs
     */

	if((reps_rc(lar, input_type, rc, size, bwidth) == \-1){
	    TROUBLE WITH CONVERSION
	}
.fi
.SH BUGS
None known.
.SH SEE ALSO
auto_pefrc(3-ESPSsp), pc_to_lsf(3-ESPSsp), 
.br
lsf_to_pc(3-ESPSsp)
.SH FUTURE CHANGES
Add cepstrum and area functions to the allowable spectral types.
.SH AUTHOR
Manual page and code by David Burton