EasyAac is an easy to use shell script which converts MP3 files in an M3U playlist to AAC+.
Usage: easyaac.sh playlist.m3u bitrate
Please note that bitrate is specfied in kbps
This script requires lame, aacplusenc and MP4Box installed. In most Linux distributions, MP4Box is provided by the package "gpac"
it can be installed in Ubuntu by issuing following command
sudo apt-get install gpac
very easy to use