This thread disapeard (seems to be a technical problem). So I just put back the valuable info that I got from it : Posted by: zeus fabianus, A new post has been made to a topic to which you have subscribed on the Elastix Forum forum Subject: 'Re:how to install G729 ?' in Forum: 'Help' Posted by: zeus You can administer your subscriptions by following the 'my profile' link on the forum home page after you have logged in on the site. From your profile you can also unsubscribe from the topic. URL: http://www.elastix.org/index.php?option ... =3708#3708 Post: I successfully added g729 codec to opteron 64 dual core machine. But i read in other posts that may be unstable so follow the guide bellow at your own risk. Adding G.729 For Free If you want to use Digium's official G.729 (low-bandwidth but very decent quality codec, 8KB/sec instead of ulaw's 64KB/sec), you need to buy a license per channel used. However, there's an open source version which seems to work really well. I recommend you install it by doing the following when connected to your Asterisk box as root: cd /usr/lib/asterisk/modules Then do ONLY ONE of the following, depending which architecture your Asterisk box's CPU is: http://kvin.lv/pub/Linux/Asterisk/ Then connect to the Asterisk console with: asterisk -r and type (adjust accordingly): load codec_g729-gcc-athlon-sse.so You should then see something like: Loaded /usr/lib/asterisk/modules/codec_g729-gcc-athlon-sse.so => (G729/PCM16 (signed linear) Codec Translator, based on IPP) == Registered translator 'g729tolin' from format g729 to slin, cost 1 == Registered translator 'lintog729' from format slin to g729, cost 6 Exit from the console with: quit Then use nano to edit /etc/asterisk/sip.conf and just below: allow=ulaw add: allow=gsm allow=g729 Then, if you still want to use G.711 (ulaw) between your box and your trunks (and between your box and your phones) for the time being until you have more time to experiment with it, go to your trunk config pages in FreePBX and add the following to the PEER DETAILS section: disallow=all allow=ulaw On each of your phone extension pages, set disallow to all and set allow to ulaw. This will force them to use only ulaw. Click the red bar and you're done. Now you're set up to use G.729 for free, but only when you're ready to try it out; to do this, you could go to your trunk config and put a semicolon at the beginning of the disallow line, which would then allow the system-wide settings (in sip.conf) to affect that trunk, which then it would start using. You could alternately change allow=ulaw to allow=g729 to force it to use only that codec. To verify what codec you're actually using, while you're on a call connect to the Asterisk console with: asterisk -r and type: sip show channels If all the steps are right g729 should work.