People sometimes send me m4a files to upload to my song database which only really supports mp3. I keep forgetting what command I use to convert so here is a record of it:
for i in *.m4a; do avconv -i "$i" -b:a 128k "${i%m4a}mp3"; done
for i in *.m4a; do avconv -i "$i" -b:a 128k "${i%m4a}mp3"; done
for i in *.m4a; do avconv -i "$i" -b:a 128k "${i%m4a}mp3"; done