EVS Configuration Detail

This section discusses aspects of OCSBC configuration that you must consider in addition to typical transcoding configuration for EVS.

Payload Type Mapping

The user enables EVS AMR-WB IO payload type mapping using the media-manager-config option audio-payload-type-mapping=yes. If the option is not present, EVS AMR-WB IO payload type mapping is disabled.

media-manager
 …
 options
audio-payload-type-mapping=yes

Furthermore, the payload-type is not critical as long as the audio-payload-type-mapping=yes option is configured. Normally the PTI used in the network is configured in the payload-type field. But the OCSBC matches against codec name/string instead of payload-type.

Adding Codecs on Egress

When there is a codec update or re-negotiation from the original codec list, the user must ensure that use of the new codecs being offered is supported by the configuration of the add-codecs-on-egress field.

codec-policy
 name CoreFacingCodecs
 allow-codecs *
add-codecs-on-egress AMR-WB::NMS:(AMR-WB::NMS)
AMR::NMS:(AMR::NMS) AMR- WB::MSC:(!AMR::MSC)
AMR::MSC:(!AMR-WB::MSC)
order-codecs AMR-WB::NMS:(AMR-WB::NMS)
AMR::NMS:(AMR::NMS) * AMR-WB::MSC AMR::MSC

In the above example, AMR::MSC and AMR-WB::MSC are media-profiles defined for AMR and AMR-WB respectively, with the specifics of the new codecs being offered for the media update or re-negotiation.

EVS Call Flow Example

The flow depicted below provides an example that uses the audio-payload-type-mapping=yes to enable payload type mapping. In addition, the flow uses add-codecs-on-egress configuration in the egress codec policy configured as EVS::PT98. The offer contains EVS in AMR-WB IO mode and the SBC adds EVS AMR-WB IO with a different payload type. The answer uses the added EVS. The offer and answer are both octet-aligned and they have intersecting mode-sets, so transcoding is not required and payload type mapping is used.

The EVS Call Flow diagram is described above.

Media Management

Additionally, mm-in-realm should be enabled in the core realm to enable transcoding for SRVCC deployments. Oracle also recommends that the user enable codec-manip-in-realm for these deployments.