On searching for how to do it, I found this page: http://www.g2support.com/how-to-enable-mp3-voicemails-in-freepbx/#comment-6728
Credit and kudos to Oliver Marshall. However, there are some errors to the script that is posted, and I will note them here, along with posting steps to enable. 99% comes from that page, but I want to post here for safekeeping for all.
GET LAME
wget http://sourceforge.net/projects/lame/files/lame/3.99/lame-3.99.5.tar.gz/download
UNTAR
tar download
GO TO LAME DIRECTORY AND MAKE IT / INSTALL
cd lame-3.99.5
./configure
make
make install
CREATE sendmailmp3 in /usr/sbin/ (below)
#! /bin/sh
# Asterisk voicemail attachment conversion script
# Revision history :
# 22/11/2010 – V1.0 – Creation by N. Bernaerts
# 07/02/2012 – V1.1 – Add handling of mails without attachment (thanks to Paul Thompson)
# 01/05/2012 – V1.2 – Use mktemp, pushd & popd
# 08/05/2012 – V1.3 – Change mp3 compression to CBR to solve some smartphone compatibility (thanks to Luca Mancino)
# 01/08/2012 – V1.4 – Add PATH definition to avoid any problem (thanks to Christopher Wolff)
# set PATH
PATH=”/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin”
# save the current directory
pushd .
# create a temporary directory and cd to it
TMPDIR=$(mktemp -d)
cd $TMPDIR
# dump the stream to a temporary file
cat >> stream.org
# get the boundary
BOUNDARY=`grep “boundary=” stream.org | cut -d'”‘ -f 2`
# cut the file into parts
# stream.part – header before the boundary
# stream.part1 – header after the bounday
# stream.part2 – body of the message
# stream.part3 – attachment in base64 (WAV file)
# stream.part4 – footer of the message
awk ‘/’$BOUNDARY’/{i++}{print > “stream.part”i}’ stream.org
# if mail is having no audio attachment (plain text)
PLAINTEXT=`cat stream.part1 | grep ‘plain’`
if [ “$PLAINTEXT” != “” ]
then
# prepare to send the original stream
cat stream.org > stream.new
# else, if mail is having audio attachment
else
# cut the attachment into parts
# stream.part3.head – header of attachment
# stream.part3.wav.base64 – wav file of attachment (encoded base64)
sed ‘7,$d’ stream.part3 > stream.part3.wav.head
sed ‘1,6d’ stream.part3 > stream.part3.wav.base64
# convert the base64 file to a wav file
dos2unix -o stream.part3.wav.base64
base64 -di stream.part3.wav.base64 > stream.part3.wav
# convert wav file to mp3 file
# -b 24 is using CBR, giving better compatibility on smartphones (you can use -b 32 to increase quality)
# -V 2 is using VBR, a good compromise between quality and size for voice audio files
lame -m m -b 24 stream.part3.wav stream.part3.mp3
# convert back mp3 to base64 file
base64 stream.part3.mp3 > stream.part3.mp3.base64
# generate the new mp3 attachment header
# change Type: audio/x-wav to Type: audio/mpeg
# change name=”msg—-.wav” to name=”msg—-.mp3″
sed ‘s/x-wav/mpeg/g’ stream.part3.wav.head | sed ‘s/.wav/.mp3/g’ > stream.part3.mp3.head
# generate first part of mail body, converting it to LF only
mv stream.part stream.new
cat stream.part1 >> stream.new
cat stream.part2 >> stream.new
cat stream.part3.mp3.head >> stream.new
dos2unix -o stream.new
# append base64 mp3 to mail body, keeping CRLF
unix2dos -o stream.part3.mp3.base64
cat stream.part3.mp3.base64 >> stream.new
# append end of mail body, converting it to LF only
echo “” >> stream.tmp
echo “” >> stream.tmp
cat stream.part4 >> stream.tmp
dos2unix -o stream.tmp
cat stream.tmp >> stream.new
fi
# send the mail thru sendmail
cat stream.new | sendmail -t
# go back to original directory
popd
# remove all temporary files and temporary directory
rm -Rf $TMPDIR
MAKE IT EXECUTABLE
chmod +x /usr/sbin/sendmailmp3
Go to Settings > Voicemail Admin
Scroll down and find the mailcmd setting. Change this to “/usr/sbin/sendmailmp3″ (without the quotes)
Submit your settings and be sure to click the Apply Config button.
Don’t send me mail on how the script works, I didn’t write it, so you make ask the original author here: http://www.g2support.com/how-to-enable-mp3-voicemails-in-freepbx/#comment-6728
Any issues with installing it, let me know. I will try and help, but I am not very patient with newbie questions, so if you don’t know your way around linux, TAR, MAKE or what chmod is, don’t bother.
Enjoy!