How to convert a m4a sound file to mp3?

The simple way to do it is:

ffmpeg -v 5 -y -i input.m4a -acodec libmp3lame -ac 2 -ab 192k output.mp3

If you want a script to wrap that, try aac2mp3, which should work for you. (The syntax for that last statement was pulled from there.) Inline code included below:

#!/bin/bash
#
# $Id: aac2mp3,v 1.2  03/30/2008 10:00 Daniel Tavares ([email protected]) - 
# Based on Script -  rali Exp $
#
#
# Convert one or more AAC/M4A files to MP3.  Based on a script example
# I found at: http://gimpel.gi.funpic.de/Howtos/convert_aac/index.html
#
ME=`basename ${0}`
FFMPEG="/usr/bin/ffmpeg"
EXT="mp4"
BITRATE="128"
do_usage() {            # explanatory text
 echo "usage: ${ME} [-b nnn] [-e ext] [-f] [-c] [-r] [-v] [-h] [file list]"
 echo "       Convert music from AAC format to MP3"
 echo "  -m /path/app  Specify the location of ffmpeg(1)"
 echo "  -b nnn        bitrate for mp3 encoder to use"
 echo "  -e ext        Use .ext rather than .m4a extension"
 echo "  -f            Force overwrite of existing file"
 echo "  -c            Delete original AAC|M4A file(s)"
 echo "  -v            Verbose output"
 echo "  -h            This information"
 echo ""
 echo "For recursive directory, use: find -name '*.${EXT}' -exec ${ME} "{}" [args]     \;"
 exit 0
 }
do_error() {
 echo "$*"
 exit 1
 }
file_overwrite_check() {
 if [ "$FORCE" != "yes" ]
 then
   test -f "${1}" && do_error "${1} already exists."
 else
   test -f "${1}" && echo "  ${1} is being overwritten."
 fi
 }
create_mp3() {  # use ffmpeg(1) to convert from AAC to MP3
 file_overwrite_check "${2}"
 test $VERBOSE && echo -n "Converting file: ${1}"
 ${FFMPEG} -v 5 -y -i "${1}" -acodec libmp3lame -ac 2 -ab ${BITRATE}k "${2}";
 if [ $? -ne 0 ]
 then
   echo ""
   echo "Error!"
   do_cleanup
   do_error "Exiting"
 fi
 test $VERBOSE && echo ".  OK"
 }
do_cleanup() {  # Delete intermediate and (optionally) original file(s)
 test ${RMM4A} && rm -f "${1}"
 test $VERBOSE && echo ".  OK"
 }
do_set_bitrate() {
 test $VERBOSE && echo -n "Setting bitrate to: $1 kbps"
 BITRATE=$1
 test $VERBOSE && echo ".  OK"
 }
GETOPT=`getopt -o l:m:b:e:cfhrv -n ${ME} -- "$@"`
if [ $? -ne 0 ]
then
 do_usage
fi
eval set -- "$GETOPT"
while true
do
 case "$1" in
   -m) FFMPEG=$2 ; shift ; shift ;;
   -b) do_set_bitrate $2 ; shift ; shift ;;
   -e) EXT=$2 ; shift ; shift ;;
   -f) FORCE="yes" ; shift ;;
   -c) RMM4A="yes" ; shift ;;
   -v) VERBOSE="yes" ; shift ;;
   -h) do_usage ;;
   --) shift ; break ;;
    *)  do_usage ;;
 esac
done
test -f $FFMPEG || do_error "$FFMPEG not found. Use \"-m\" switch."
if [ $# -eq 0 ]
then                    # Convert all files in current directory
 for IFILE in *.${EXT}
 do
   if [ "${IFILE}" == "*.${EXT}" ]
   then
     do_error "Not found ${EXT} in this folder."
   fi
   OUT=`echo "${IFILE}" | sed -e "s/\.${EXT}//g"`
   create_mp3 "${IFILE}" "${OUT}.mp3"
   do_cleanup "${IFILE}" 
 done
else                    # Convert listed files
 for IFILE in "$*"
 do
   test -f "${IFILE}" || do_error "${IFILE} not found."  
   OUT=`echo "${IFILE}" | sed -e "s/\.${EXT}//g"`    
   create_mp3 "${IFILE}" "${OUT}.mp3"
   do_cleanup "${IFILE}"    
 done    
fi   
exit 0

This worked for me on Ubuntu 14.04:

avconv -i input.m4a ouptut.mp3

To obtain the avconv command, install libav-tools :

sudo apt-get install libav-tools

SoundConverter can do this without having to mess around on the command-line, and it's available in the Ubuntu Software Center:

I needed an alternate solution because - my files were sitting in recursive subdirectories - I had spaces in paths.

So I eventually settled for :

 find . -type f -name '*.m4a' -exec bash -c 'avconv -i "$0" "${0/%m4a/mp3}"' '{}' \;

Then deleted the original files :

find . -type f -name '*.m4a' -exec bash -c 'rm "$0"' '{}' \;

I created a script to do this.

My requirements were:

• Must maintain as many tags as possible
• Must retain album artwork if exists
• Must be 320K mp3s

Works on all m4a files in a directory, and outputs the new shiny Mp3s into a folder the script creates called Mp3. Warning; this script overwrites existing Mp3s in the output folder if they have the same name. Also uses files 'metadata.txt' and 'metadata2.txt' as temp files.

You'll need to install avconv if it doesn't exist already.

I couldn't figure out how to persist the 'Year' tag into ID3v1 tags, so I didn't enable that option.

#!/bin/bash
files=*.m4a
#create output folder if it doesnt exist
if [ ! -d Mp3 ]; then
        mkdir Mp3
fi

for file in $files; do
        mp3File=${file/%m4a/mp3}
        avconv -y -i "${file}" -f ffmetadata metadata.txt
        sed -e 's/^date=\(.*\)$/TYER=\1/' -e 's/^major_brand=.*$//' -e 's/^minor_version=.*$//' -e 's/^creation.*$//' -e 's/^compatible.*$//' -e 's/^encoder=.*$//' <metadata.txt >metadata2.txt
        avconv -y -i "${file}" -i metadata2.txt -ab 320k -map_metadata 1 -id3v2_version 3 "Mp3/${mp3File}"
done

Save it as 'convert.b', and then run the script by typing:

% bash convert.b

Sometimes avconv and ffmpeg don't work so cleanly, so:

sudo apt-get install faad lame
faad myfile.m4a -w | lame - myfile.mp3

always works for me.

Old question, but I don't see a very simple solution: Use VLC

In VLC you can load a .m4a file and convert it to .MP3 very easyllie.

1. Open VLC (no need to load any file)

2. Click on Media or press CTRL+R

3. Click on Conver/Save

4. On Profile select MP3

5. Select destination

6. Click on Start and wait. To know if it doing something or not, look at the time bar.

I hope this will be usefull for somebody.

In Ubuntu 20.04 the original command works out of the box:

ffmpeg -i music.m4a music.mp3

You probably need the unrestricted libav packages in medibuntu repository. Personally I would compile the latest ffmpeg with all codecs, as easy as 123 http://ubuntuforums.org/showthread.php?t=786095

On my L-Ubuntu, libav-tools was not available. I installed winff :

sudo apt-get install winff

which provides a graphical tool to convert audio and video files from and into many different formats.

Just tried : it works fine for .m4a to .mp3 :-)

Otherwise vlc also does a great job playing .m4a files :

sudo apt-get install vlc