HOW TO CONVERT MP4 FILE FOR MP3

First of all, start apt of packet:

sudo apt-get install ffmpeg libavcodec-extra-53

When finish do that:

ffmpeg -i filename.mp4 filename.mp3

ffmpeg -i filename.mp4 -b:a 192K -vn filename.mp3 

if you want create a script do that;

############################START SCRIPT ##############################################

#!/bin/bash
MP4FILE=$(ls ~/Music/ |grep .mp4)
for filename in $MP4FILE
do 
 name=`echo "$filename" | sed -e "s/.mp4$//g"`
 ffmpeg -i ~/Music/$filename -b:a 192K -vn ~/Music/$name.mp3
done

############################END SCRIPT ##############################################