To install the G.729 codec, you must first order licenses from Digium. They will then send you an email with the license key. When you have received this, do:

• /opt/enswitch/current/bin/enswitch_install g729

and follow the menus to register the license key. When finished, add the following line to the bottom of the [general] section in /etc/asterisk/sip.conf:

allow = g729

then restart Asterisk if you have already started it.