AC3 to MP3 Converter

Convertion audio in films from AC3 to MP3
#!/bin/bash

if [ $# -eq 0 ]; then
 echo "---------------------------------------------";
 echo "---  AC3 to MP3 video converter script    ---";
 echo "---------------------------------------------";
 echo "Usage: $0 [directory]";
 exit 1;
fi

find "$1" -type f|while read f; do
 if [ `file "$f" | grep -c "audio: Dolby AC3"` == 1 ]; then
  mkdir "$1/_original"
  avconv -async 30 -i "$f" -vcodec copy -acodec libmp3lame -ar 48000 -ab 256k -ac 2 -r 30 "${f%.*}""_mp3.""${f##*.}"
  mv "$f" "$1/_original/"
 fi
done