this script convert m4a audio file to mp3 file

m4a_to_mp3.sh

#!/bin/bash
input=$1

if [[ -z "$input" ]] ; then
    echo "Usage:  $0 [m4a filepath]"
    exit
fi

if [[ -z $(which faad) ]] ; then 
    echo "Can not found faad , please install it"
    exit
fi

if [[ -z $(which lame) ]] ; then 
    echo "Can not found lame , please install lame"
    exit
fi

noext=$(echo $input | sed -e 's/.m4a$//g' )

faad -w "$input" > "$noext.wav"

# -r : for assume raw pcm data
# -V : for varialbe rate
lame -r -h -V 6 "$noext.wav" "$noext.mp3"
# lame -h -b 64 "$noext.wav" "$out.mp3"
rm -v "$noext.wav"