Convert AC3 to MP3 in a MKV file

ac3tomp3.sh

#!/bin/bash
# script: convert AC3 to MP3 in MKV container
# author: bert2002 <s.wirth@itbert.de>

FILE=$1
FILENAME=$(basename $FILE mkv)
AC3AUDIO=$(mkvmerge --identify $FILE |grep "AC3" | awk -F':' '{print $1}' | awk '{print $3}')

mkvextract tracks $FILE $AC3AUDIO:${FILENAME}ac3
ffmpeg -i ${FILENAME}ac3 -acodec libmp3lame -ab 160k -ac 2 ${FILENAME}mp3

mkvmerge -o ${FILENAME}NEW.mkv $FILE ${FILENAME}mp3

MP3AUDIO=$(mkvmerge --identify ${FILENAME}NEW.mkv |grep MP3 | awk -F':' '{print $1}' | awk '{print $3}')
mkvmerge -o ${FILENAME}NEW.mkv.tmp -a $MP3AUDIO ${FILENAME}NEW.mkv && mv ${FILENAME}NEW.mkv.tmp ${FILENAME}NEW.mkv