Some of my library was in m4a files, which I have problems to play, furthermore I prefer having everything in mp3 format.

So I wrote the following script:

echo "Dependencies: mplayer and lame"
if [ $# -lt 1 ]; then
	echo "Usage: sh m4a2mp3.sh '/path/to/files'"
else 
	echo "This could take sometime. Converting to 320kbps MP3 files..."
	sleep 1
	cd "$1"
	for i in *.m4a; do mplayer -ao pcm "$i" -ao pcm:file="$i.wav"; done
	for i in *.wav; do lame -h -b 320 "$i" "$i.mp3"; done
	echo "Cleaning the house..."
	rm -rf *.m4a
	rm -rf *.wav
fi
echo "All files converted. Thank you."

Usage is pretty straightforward:

sh m4a2mp3.sh /path/to/your/songs

The only dependencies, as you can see also in the script are mplayer and lame

You can install them with the following command:

# Yum based (Fedora, CentOS, SuSE)
yum install mplayer lame
# Apt based (Debian, Ubuntu, Mint) (NOT TESTED)
apt-get install mplayer lame

As always, you also can find the script on my Github.