# v_lin2pcma

## PURPOSE

V_LIN2PCMA Convert linear PCM to A-law P=(X,M,S)

## SYNOPSIS

function p=v_lin2pcma(x,m,s)

## DESCRIPTION

    V_LIN2PCMA Convert linear PCM to A-law P=(X,M,S)
        pcma = v_lin2pcma(lin) where lin contains a vector
        or matrix of signal values.
        The input values will be converted to integer
        A-law pcm vlues in the range 0 to 255 and the XORed with m
        (default m=85).

        Input values are multiplied by the scale factor s:

               s        Input Range

               1        +-4096
            2017.396342    +-2.03033976 (default)
            4096        +-1

        Input values outside the selected range will be clipped.

        The default value of the scale factor is 2017.396342 which equals
        sqrt((1120^2 + 2624^2)/2). This factor follows ITU standard G.711 and
        the sine wave with PCM-A values [225 244 244 225 97 116 116 97]
        has a mean square value of unity corresponding to 0 dBm0.

        See also PCMA2LIN, LIN2PCMA, LIN2PCMU

## CROSS-REFERENCE INFORMATION

This function calls:

This function is called by:

- v_writewav V_WRITEWAV Creates .WAV format sound files FIDX=(D,FS,FILENAME,MODE,NSKIP,MASK,MAD)

## SOURCE CODE

    0001 function p=v_lin2pcma(x,m,s)
    0002 %V_LIN2PCMA Convert linear PCM to A-law P=(X,M,S)
    0003 %    pcma = v_lin2pcma(lin) where lin contains a vector
    0004 %    or matrix of signal values.
    0005 %    The input values will be converted to integer
    0006 %    A-law pcm vlues in the range 0 to 255 and the XORed with m
    0007 %    (default m=85).
    0008 %
    0009 %    Input values are multiplied by the scale factor s:
    0010 %
    0011 %           s        Input Range
    0012 %
    0013 %           1        +-4096
    0014 %        2017.396342    +-2.03033976 (default)
    0015 %        4096        +-1
    0016 %
    0017 %    Input values outside the selected range will be clipped.
    0018 %
    0019 %    The default value of the scale factor is 2017.396342 which equals
    0020 %    sqrt((1120^2 + 2624^2)/2). This factor follows ITU standard G.711 and
    0021 %    the sine wave with PCM-A values [225 244 244 225 97 116 116 97]
    0022 %    has a mean square value of unity corresponding to 0 dBm0.
    0023 %
    0024 %    See also PCMA2LIN, LIN2PCMA, LIN2PCMU
    0025
    0026
    0027
    0028 %      Copyright (C) Mike Brookes 1998
    0029 %      Version: $Id: v_lin2pcma.m 10865 2018-09-21 17:22:45Z dmb $
    0030 %
    0031 %   VOICEBOX is a MATLAB toolbox for speech processing.
    0032 %   Home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html
    0033 %
    0034 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    0035 %   This program is free software; you can redistribute it and/or modify
    0036 %   it under the terms of the GNU Lesser General Public License as published by
    0037 %   the Free Software Foundation; either version 3 of the License, or
    0038 %   (at your option) any later version.
    0039 %
    0040 %   This program is distributed in the hope that it will be useful,
    0041 %   but WITHOUT ANY WARRANTY; without even the implied warranty of
    0042 %   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    0043 %   GNU Lesser General Public License for more details.
    0044 %
    0045 %   You can obtain a copy of the GNU Lesser General Public License from
    0046 %   https://www.gnu.org/licenses/ .
    0047 %
    0048 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    0049
    0050 if nargin<3
    0051   s=2017.396342;
    0052   if nargin<2 m=85; end
    0053 end
    0054
    0055 y=x*pow2(s,-6);
    0056 y=(abs(y+63)-abs(y-63))/2;
    0057 q=floor((y+64)/64);
    0058 [a,e]=log2(abs(y));
    0059 d = (e+abs(e))/2;
    0060 p=128*q+16*d+floor(pow2(a,e-d+5));
    0061 if m p=bitxor(p,m); end;