bash script extracting audio from mp4 and conditionaly convert or copy to mp3

convertMp4ToAudioMp3.sh

#http://askubuntu.com/questions/221026/how-can-i-batch-extract-audio-from-mp4-files-with-ffmpeg-without-decompression#221069
mkdir -p outputmp3
# current directory has to contain at least one .mp4 file 
for vid in *.mp4; do
   codec="$(ffprobe -v error -select_streams a:0 -show_entries stream=codec_name -print_format csv=p=0 "$vid")"
   case "$codec" in
    mp3    ) filetype=mp3 ;;
    *      ) filetype= ;;
   esac

   if [ "$filetype" ]; then 
    ffmpeg -i "$vid" -vn -acodec copy outputmp3/"${vid%.*}"."$filetype"
   else
    ffmpeg -i "$vid" -vn -acodec mp3 outputmp3/"${vid%.*}".mp3
   fi
done