pctolsf.3

speech signal process tools

.\" Copyright (c) 1986-1990 Entropic Speech, Inc.
.\" Copyright (c) 1991 Entropic Research Laboratory, Inc. All rights reserved.
.\" @(#)pctolsf.3	1.5 29 Jul 1991 ESI/ERL
.ds ]W (c) 1991 Entropic Research Laboratory, Inc.
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.TH PC_TO_LSF \3-ESPSsp 29 Jul 1991
.SH NAME

pc_to_lsf \- convert linear prediction coefficients to line spectral frequencies
.SH SYNOPSIS
.ft B
int
pc_to_lsf(pc, lsf, order, bandwidth, freq_res)
.br
float   pc[], bandwidth, lsf[], freq_res;
.br
int     order;
.SH DESCRIPTION
This routine computes the line spectral frequencies
.I lsf
(see [1]) that correspond to the input vector
.I pc
of linear prediction coefficients,
also known as autoregressive filter coefficients
or prediction-error filter coefficients.
The convention adopted is that the first such coefficient is \-1,
and it does not appear in the input vector.
The argument
.I order
is the analysis filter order\*-i.e. the number of explicitly given input
.I pc
parameters and output 
.I lsf
parameters\*-and
.I bandwidth
should equal one-half the sampling frequency of the original sampled data.
The function uses a search with a frequency spacing
.I freq_res.
Legitimate values for
.I freq_res
range between 1 and 100 Hz for a signal bandwidth of 4000 Hz.
.SH REFERENCES
[1] G. S. Kang and L. J. Fransen,
.I
Low-Bit Rate Speech Encoders Based on Line-Spectrum Frequencies (LSFs),
NRL Report 8857, Naval Research Laboratory, Washington, D.C., January, 1985.
.SH AUTHOR
Manual page D. Burton