Asterisk as Codec converter


Does anyone now how to setup the Asterisk as a codec converter.

Situation: A VoiP carrier only support the codec G711a and G711u. On a VoIP PABX (3th party brand) 9.000 UA’s are registered. I want to terminate some traffic to this VOIP carrier but there are a variety of codecs used.

The VoIP carrier only support sipconnect v1.0 with G711a and G711u. So there is no connection by E1’s. just voip to voip.

Anny suggestions would be welcome.

Kind regards,


This should work out of the box. Have you tried? If so, and it failed, you’ll need to provide detailed debugging information.

Basically the two sides will negotiate codecs agreeable to them and Asterisk will then try to convert.

In practice, you might want to prevent the PABX using some codecs, by setting allowed and denied ones in sip.conf.

Ideally you should choose between the A and µ variants of G.711 according to in which country the VoIP provider connects to the PSTN and only enable the relevant one, as transcoding between them at the PSTN boundary will cause some, small, extra degradation.