The Peeredge Switch currently supports the following audio codecs.
G.711ulaw | G.722 | G.726-32 | G.729.1 | L16 | iLBC |
G.711alaw | G.723 | G.726-40 | G.729D | L20 | PCMA-WB |
G.729 | G.726-16 | G.728 | GSM | L24 | PCMU-WB |
G.719 | G.726-24 | G.729E | L8 | LPC | Speex |
Most PSTN carriers only offer support of the G.711ulaw, G.711alaw, and the G.729 codecs.
For inbound PSTN calls to the customer, by default the Peeredge Switch will only forward the PSTN vendor supported codecs to the customer’s SBC/PBX. The Peeredge Switch can be configured to filter out codecs offered by the upstream carrier and/or add additional codecs in the SIP Invite w/SDP offer to the customer SBC/PBX.
For outbound PSTN calls, by default the Peeredge Switch will always select the first codec in the list of codecs offered in the customer’s SIP Invite w/SDP message that the upstream carrier supports. If there is no upstream carrier supported codecs in the list of codecs offered in the SIP Invite w/SDP message, then transcoding can be enabled on the Peeredge Switch.
Recommendations
Since most PSTN carriers only support the G.711ulaw, G.711alaw, and the G.729 codecs, 46Labs STRONGLY RECOMMENDS only including these codecs in the SIP Invite w/SDP. Our testing with several enterprise SBC/PBX systems has shown there are often “hidden” design challenges in complex call flows when using codecs not supported by upstream carriers.
When voice quality is the primary design consideration, 46Labs recommends using the G.711 codec.
When minimizing network bandwidth usage is the primary design consideration, the G.729 codec can be configured as the preferred codec.
The Peeredge Switches do not support video codecs. Video codecs should not be included in the SDP of any SIP messages sent to the Peeredge Switches.