Don't know about mpg123 but I found that using a lame script "mlame" coverts all my .wav to .mp3 automatically:
~/kencaz/./mlame -r -o "-v -V 0 -b 112" *.wav *.mp3
This will convert all file in my current foder from .wav to .mp3. I don't remember where I got the script but it's kinda hard to find so I'll include it here. You'll have to save it to a file then change permissions as usual...
#!/bin/bash
#!/usr/local/bin/bash
############################################################################
#
# Run the LAME encoder on multiple files, with option to delete .wav files
# after encoding. "mlame -h" will give instructions.
#
# Robert Hegemann <Robert.Hegemann@gmx.de>
#
############################################################################
mp3coder="lame"
options="-h -d -m j -b 128"
rmsrc=false
helptext="\
\nThis script runs the LAME mp3 encoder on multiple files: \n\n\
$0 [options] <file 1> ... <file n>\n\
\n\
options:\n\
-h this help text\n\
-r remove files after encoding\n\
-o \"<lame options>\" overrides script default options \"${options}\"\n\
\n\
example:\n\
$0 -r -o \"-v -V 0 -b 112\" a*.wav z*.aif\n\
\n\
"
# process command-line options
# this could be extended to fake the
# commandline interface of the mp3encoder
while getopts "
:r" optn; do
case $optn in
o ) options=$OPTARG # replace default options
;;
r ) rmsrc=true
;;
\? ) printf "$helptext"
exit 1
;;
esac
done
shift $(($OPTIND - 1))
# process input-files
for filename in "$@"; do
case $filename in
*[*?]* ) # means shell couldnīt extend *.wav, etc.
echo "warning: no $filename file(s) found"
;;
*[.][wW][aA][vV] )
name=${filename%[.][wW][aA][vV]}
if $mp3coder $options "$filename" "${name}.mp3"
then
if [ $rmsrc = true ]; then
rm -f "$filename"
fi
fi
;;
*[.][aA][iI][fF] )
name=${filename%[.][aA][iI][fF]}
if $mp3coder $options "$filename" "${name}.mp3"
then
if [ $rmsrc = true ]; then
rm -f "$filename"
fi
fi
;;
* )
if $mp3coder $options "$filename" "${filename}.mp3"
then
if [ $rmsrc = true ]; then
rm -f "$filename"
fi
fi
;;
esac
done
