Installing iLBC codec in Asterisk

Archived from groups: comp.dcom.voice-over-ip (More info?)

Dear all,
Could anyone suggest how to install iLBC codec to be used with Asterisk?
I've heard that it's much better than the standard GSM.
(offers much better quality without much increase in bandwith)

When I change the

allow=gsm ; Allow codecs in order of preference

TO

allow=ilbc ; Allow codecs in order of preference

in "general" section of sip.conf, it simply jumps to the next codec (ulaw).

Any ideas?

Thanks a lot,
Roman Zhovtulya