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m4a is the file extension for the proprietary audio format mostly used by that iTunes thingy. A conversion to more player friendly (usb mp3player for example) formats like mp3 or ogg only works, if the aac's aren't DRM protected. For the conversion you need the following tools installed:

mplayer (with faad2 support compiled in!)
faad2
for mp3: lame
for ogg: oggenc (vorbis-tools)

[edit] aac/m4a to wav

In case you only want to convert a single file:

mplayer -ao pcm inputfile.m4a -ao pcm:file="outfile.wav"

or - if you want to use faad:

faad inputfile.aac

If you want to convert all files in a directory, you can use this little script:

#!/bin/bash
# 
# m4a2wav
# 
for i in *.m4a; do
   # out=$(echo $i | sed -e 's/.m4a//g')
    mplayer -ao pcm "$i" -ao pcm:file="${i%.m4a}.wav"
done

This also seems to work for converting all aac/m4a files in a directory (please note that this will also search sub-directories):

find -name '*.m4a' -exec faad '{}' ';'

Note: the inputfiles shouldn't contain spaces (maybe we should sed those away too in the script? :))

[edit] wav to mp3

Now we can convert the wav's to mp3 or ogg or whatever we like. For example to convert to mp3 we can use this second script:

#!/bin/bash 
# 
# wav2mp3
# 
for i in *.wav; do
    #out=$(ls $i | sed -e 's/.wav//g')
    #out=$(echo $i | sed -e 's/.wav$//')
    #lame -h -b 192 "$i" "$out.mp3"
    lame -h -b 192 "$i" "${i%.wav}.mp3"
done

That's it ;)

[edit] mp3 to wav

Now we can convert mp3 to wav.

mpg123 -w output.wav input.mp3

[edit] aac2ogg script

There is also a python script available at http://www.samsix.com/scripts/aac2ogg for converting to ogg vorbis with tags intact. It will also automatically determine the bitrate of the original file and use an appropriate quality setting to match. This is based on the perl script http://zarb.org/~zerodogg/scripts/aac2ogg.

[edit] aac2mp3 script

Ok here is a little script that does all that in one step. THX to Nico for a good working one, and BIG thanks to Reto L. for a new improved version that comes with switches for program paths, bitrate and more useful options! see 'aac2mp3 -h' for a help text ;)

#!/bin/bash

#
# $Id: aac2mp3,v 1.2 2005/08/22 15:32:34 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}`

AAC2WAV="/usr/bin/mplayer"
WAV2MP3="/usr/bin/lame"

EXT="m4a"
BITRATE="192"

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 "  -l /path/app  Specify the location of lame(1)"
  echo "  -m /path/app  Specify the location of mplayer(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 "  -s            Keep intermediate .wav file(s)"
  echo "  -v            Verbose output"
  echo "  -h            This information"
  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_wav() {  # use mplayer(1) to convert from AAC to WAV
  file_overwrite_check "${2}"

  test $VERBOSE && echo -n "Creating intermediate WAV file"

  ${AAC2WAV} -really-quiet -ao pcm "${1}" -ao pcm:file="${2}"
  if [ $? -ne 0 ]
  then
    echo ""
    echo "Conversion to WAV (${AAC2WAV}) failed."
    do_cleanup
    do_error "Exiting"
  fi

  test $VERBOSE && echo ".  OK"
  }

create_mp3() {  # use lame(1) to convert from WAV to MP3
  file_overwrite_check "${2}"

  test $VERBOSE && echo -n "Creating output MP3 file"

  ${WAV2MP3} -h -b ${BITRATE} -S "${1}" "${2}"
  if [ $? -ne 0 ]
  then
    echo ""
    echo "Conversion to MP3 (${WAV2MP3}) failed."
    do_cleanup
    do_error "Exiting"
  fi

  test $VERBOSE && echo ".  OK"
  }

do_cleanup() {  # Delete intermediate and (optionally) original file(s)
  test $VERBOSE && echo -n "Deleting intermediate file"
  test ${SAVEWAV} || rm -f "${2}"
  test ${RMM4A}   && rm -f "${1}"
  test $VERBOSE && echo ".  OK"
  }

do_set_bitrate() {
  test $VERBOSE && echo -n "Setting output 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
    -l) LAME=$2 ; shift ; shift ;;
    -m) MPLAYER=$2 ; shift ; shift ;;
    -b) do_set_bitrate $2 ; shift ; shift ;;
    -e) EXT=$2 ; shift ; shift ;;
    -f) FORCE="yes" ; shift ;;
    -c) RMM4A="yes" ; shift ;;
    -s) SAVEWAV="yes" ; shift ;;
    -v) VERBOSE="yes" ; shift ;;
    -h) do_usage ;;
    --) shift ; break ;;
     *)  do_usage ;;
  esac
done

test -f $LAME    || do_error "$LAME not found. Use \"-l\" switch."
test -f $MPLAYER || do_error "$MPLAYER 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 "No files with extension ${EXT} in this directory."
    fi

    OUT=`echo "${IFILE}" | sed -e "s/\.${EXT}//g"`

    create_wav "${IFILE}"   "${OUT}.wav"
    create_mp3 "${OUT}.wav" "${OUT}.mp3"
    do_cleanup "${IFILE}"   "${OUT}.wav"

  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_wav "${IFILE}" "${OUT}.wav"	 
    create_mp3 "${OUT}.wav" "${OUT}.mp3"	 
    do_cleanup "${IFILE}" "${OUT}.wav"	 
  done	 
fi	 
exit 0

[edit] aac2mp3 - faster

This script, based on the above, is faster because it uses ffmpeg for conversion. ffmpeg converts directly to mp3, and does not create an intermediate wav file. You will have to compile ffmpeg with LAME enabled; check ffmpeg's ./configure --help to enable proper libs.

#!/bin/bash
#
# $Id: aac2mp3,v 1.2  03/30/2008 10:00 Daniel Tavares (dantavares@gmail.com) - 
# 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

[edit] ogg2mp3

cf. http://forums.gentoo.org/viewtopic-t-463068-highlight-.html for my bash script

[edit] Set the Tags on .mp3 Files After Conversion

This little script is handy to set the artist, album, and song information on all the .mp3 files in a directory, after you have converted them from some other format, or because the tags are screwed up, causing your mp3 player to sort the songs incorrectly.

#!/bin/bash
# tagmp3
# Tags every .mp3 in the directory with the band and
# album names, and creates a song title by stripping
# the .mp3 extension from the file name.
# Call like this:
# tagmp3 bandname albumname
for i in *.mp3; do
    SONG=`basename "$i" .mp3`
    id3v2 --album "$2" --artist "$1" --song "$SONG" "$i"
done

[edit] Convert m4a to mp3, setting tag information

This script converts all the .m4a files in a directory to .mp3, setting the artist and album info to the values you specify on the command line, and setting the title info using the file name. Glues together several of the above scripts

#!/bin/bash
# m4a2mp3
# Convert all m4a to mp3, assign tags, delete intermediary
# wav files
# Tags every .mp3 in the directory with the band and
# album names, and creates a song title by stripping
# the .mp3 extension from the file name.
# Call like this:
# m4a2mp3 bandname albumname
m4a2wav
wav2mp3
tagmp3 "$1" "$2"
rm *.wav

[edit] aac/m4a/mp4/rm/ram/any to mp3

Using mplayer and lame :

#! /bin/bash
#
# Converts an Audio file to a MP3 and adds an ID3 tag.
#
# Usage: audio2mp3 infile [outfile]
#
IFS=";" title_author=(`mplayer -vc null -vo null -ao pcm:fast -ao pcm "$1" -ao pcm:file="$1.wav" 2>&1 | awk -F: 'BEGIN { ORS = ";" } ; $1 ~ /name|author/ { print $2 }'`)
author=${title_author[0]}
title=${title_author[1]}
echo "Author: $author"
echo "Title: $title"
lame "$1".wav "$2" --tt "$title" --ta "$author"
rm "$1".wav

Enjoy ;-)

[edit] Suse 11.1 bash script mp4 to mp3

Using mplayer and lame :

#! /bin/bash
#
# Converts all MP4 files in the current directory to MP3s.
#
for f in *.MP4; do
 newname=`echo $f | tr ' ' '_' `
 mv "$f" $newname
 f=$newname
 mplayer $f -ao pcm:file=tmp.wav
 lame -b 128 -q 2 tmp.wav ${f/.MP4/.mp3}
 rm -f tmp.wav
done

Howto:convert aac/mp4 to wav/mp3/ogg on Linux

From Linux Multimedia Wiki

Contents

[edit] aac/m4a to wav

[edit] wav to mp3

[edit] mp3 to wav

[edit] aac2ogg script

[edit] aac2mp3 script

[edit] aac2mp3 - faster

[edit] ogg2mp3

[edit] Set the Tags on .mp3 Files After Conversion

[edit] Convert m4a to mp3, setting tag information

[edit] aac/m4a/mp4/rm/ram/any to mp3

[edit] Suse 11.1 bash script mp4 to mp3

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