# v_lpcar2rf

## PURPOSE

V_LPCAR2RF Convert autoregressive coefficients to reflection coefficients AR=(RF)

## SYNOPSIS

function rf=v_lpcar2rf(ar)

## DESCRIPTION

    V_LPCAR2RF Convert autoregressive coefficients to reflection coefficients AR=(RF)

     Input:   ar(:,p+1)  Autoregressive coefficients
     Output:  rf(:,p+1)  Reflection coefficients with rf(:,1)=1

## CROSS-REFERENCE INFORMATION

This function calls:

This function is called by:

- v_lpcar2rr V_LPCAR2RR Convert autoregressive coefficients to autocorrelation coefficients RR=(AR,P)

## SOURCE CODE

    0001 function rf=v_lpcar2rf(ar)
    0002 %V_LPCAR2RF Convert autoregressive coefficients to reflection coefficients AR=(RF)
    0003 %
    0004 % Input:   ar(:,p+1)  Autoregressive coefficients
    0005 % Output:  rf(:,p+1)  Reflection coefficients with rf(:,1)=1
    0006
    0007
    0008 %      Copyright (C) Mike Brookes 1997
    0009 %      Version: $Id: v_lpcar2rf.m 10865 2018-09-21 17:22:45Z dmb $
    0010 %
    0011 %   VOICEBOX is a MATLAB toolbox for speech processing.
    0012 %   Home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html
    0013 %
    0014 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    0015 %   This program is free software; you can redistribute it and/or modify
    0016 %   it under the terms of the GNU Lesser General Public License as published by
    0017 %   the Free Software Foundation; either version 3 of the License, or
    0018 %   (at your option) any later version.
    0019 %
    0020 %   This program is distributed in the hope that it will be useful,
    0021 %   but WITHOUT ANY WARRANTY; without even the implied warranty of
    0022 %   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    0023 %   GNU Lesser General Public License for more details.
    0024 %
    0025 %   You can obtain a copy of the GNU Lesser General Public License from
    0026 %   https://www.gnu.org/licenses/ .
    0027 %
    0028 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    0029
    0030 [nf,p1] = size(ar);
    0031 if p1==1
    0032    rf=ones(nf,1);
    0033 else
    0034    if any(ar(:,1)~=1)
    0035       ar=ar./ar(:,ones(1,p1));
    0036    end
    0037    rf = ar;
    0038    for j = p1-1:-1:2
    0039       k = rf(:,j+1);
    0040       d = (1-k.^2).^(-1);
    0041       wj=ones(1,j-1);
    0042       rf(:,2:j) = (rf(:,2:j)-k(:,wj).*rf(:,j:-1:2)).*d(:,wj);
    0043    end
    0044 end
    0045