Prioritizing Coder List in SDP Offer

In addition to restricting the use of coders using Allowed Audio Coders Groups (see Configuring Allowed Audio Coder Groups), you can also prioritize the coders listed in the SDP offer. This feature is referred to as Coder Preference and applies to both SBC legs:

■

Incoming SDP offer: The device arranges the coder list in the incoming SDP offer according to the order of appearance of the Allowed Audio Coders Group that is associated with the incoming dialog. The coders listed higher up in the group take preference over ones listed lower down. To configure this, configure the 'Allowed Coders Mode' parameter in the associated IP Profile to Preference or Restriction and Preference. If you configure the parameter to Preference, the coders in the SDP offer that also appear in the Allowed Audio Coders Group are listed first in the SDP offer, and the coders in the SDP offer that do not appear in the Allowed Audio Coders Group are listed after the Allowed coders in the SDP offer. Therefore, this setting doesn't restrict coder use to Allowed coders, but uses (prefers) the Allowed coders whenever possible.

■

Outgoing SDP offer: If only Allowed coders are used, the device arranges the coders in the SDP offer as described above. However, if Extension coders are also used, the coder list is arranged according to the SBCPreferencesMode parameter. Depending on the parameter's settings, the Extension coders are added after the Allowed coders according to their order in the Allowed Audio Coders Group, or the Allowed and Extension coders are arranged according to their position in the Allowed Audio Coders Group.