extract audio from mp4 files and convert it to mp3 format

avi_to_mp3.sh

#!/bin/bash
#
# extracts audio from all videos in current folder and saves in mp3
# based on http://ubuntuforums.org/showthread.php?t=1411144
#

 
SAVEIFS=$IFS
IFS=$(echo -en "\n\b")
 
for i in `find . -type f -iname "*.avi" -print`; do
echo $i
NAME=`echo $i | sed  -e 's/\.\///' -e  's/\.avi//g' `
echo "doing '$NAME'"
vout=mp3s/${NAME}.mp3

if [ ! -f $vout ]; then
    echo 'converting to mp3'

    mencoder -of rawaudio -ovc copy -oac mp3lame -o "${vout}" "${NAME}".avi
fi
done
 
IFS=$SAVEIFS

convert_mp4_to_mp3.sh

#extracts audio from mp4 files 
#assumes that audio is in acc (m4a) format and converts it to mp3
#mp4 audio format can be checked with ffmpeg -i fss1.mp4

mkdir -p mp3s
mkdir -p m4a 

SAVEIFS=$IFS
IFS=$(echo -en "\n\b")

for i in `find . -type f -iname "*.mp4" -print`; do
echo $i
NAME=`echo $i | sed  -e 's/\.\///' -e  's/\.mp4//g' `
echo "doing '$NAME'"

if [ ! -f m4a/${NAME}.m4a ]; then
    ffmpeg -i $i -vn -acodec copy  m4a/${NAME}.m4a
fi
if [ ! -f mp3s/${NAME}.mp3 ]; then
    echo 'converting to mp3'
    faad --stdio m4a/${NAME}.m4a | lame --preset standard - "mp3s/${NAME}.mp3"
fi
done

IFS=$SAVEIFS