By default, all IP Office IP trunks and extensions use automatic codec negotiation. The default negotiation order varies depending on the type of SD card configured.

• With an IPO MU_LAW SD card, the default negotiation order is G711.MU_LAW, G711 A_LAW, G729a, and G723.1.
• With an IPO A_LAW SD card, the default negotiation order is G711.A_LAW, G711.MU_LAW, G729a, and G723.1.

Calls to and from IP devices can require conversion to the audio codec format being used by the IP device. For IP Office systems, this conversion is done by voice compression channels. The voice compression channels support the common IP audio codecs G711, G723 and G729a. For more information about configuring codecs and voice compression channels, see Deploying Avaya IP Office™ Platform as an Enterprise Branch with Avaya Aura® Session Manager.

The following table lists the default codecs available and the other options you can select for each codec.

Some calls and media flows do not consume WAN, but others do. For calls that consume WAN bandwidth, codec selection is an important factor in determining the amount of bandwidth consumed and the audio quality of the call. The G729 codec consumes less bandwidth but can result in reduced audio quality. Depending on the needs of the enterprise, the audio quality with the G729 codec may not be acceptable. The G711 codec provides optimal audio quality, but consumes more bandwidth. The amount of bandwidth consumed by different codecs is the same for Avaya Aura® Communication Manager and IP Office.