23 Local Media Playback

Ringback refers to the media playback of a certain tone informing callers that their calls are in progress. In typical deployments, remote endpoints or media servers handle ringback generation, leaving the Oracle Communications Session Border Controller (SBC) to proxy RTP. You can alternatively configure the SBC as the producer for environments where endpoints or media servers do not support ringback generation, or if you require different ringback.

Because you can also use this capability for music-on-hold, announcements, interrupting media for notifications and so forth, this SBC capability is referred to as local medial playback.

When you configure the SBC to generate ringback locally, you enable it to produce RTP media on a media flow called ringback tone (RBT) from a session-agent, sip-interface or realm-config, using typical precedence when determining which configuration to use if there are overlapping configurations. There are other criteria to determine which configuration to use described herein. These are generally characterized as "closest to the target".

The SBC can produce local media playback using one of two methods:

  • Transcoding based playback: The SBC uses local transcoding resources to produce RTP.
  • SPL based playback: The SBC generates RTP using SPL resources.

You can only use one method on an SBC at a time.

There are two components of RBT configuration for both the SPL and transcoding-based methods:
  • Triggers: Specifies when the SBC plays the media file:
    • Transcoding-based RBT: Configured with the ACLI ringback-trigger parameter
    • SPL: Set as parameters to the spl-option
  • Media: Specifies the local media file that the SBC plays:
    • Transcoding-based RBT: Configured with the ACLI ringback-file parameter
    • SPL: Configured with ACLI playback-config elements and applied as a parameter to the spl-option

You can also use local media playback for network announcements alongside transcoding-based RBT (network announcements always use transcoding resources).

You configure network announcements by:

  1. Creating an error-announcement-map on the session router. The entries in this configuration element map SIP and Q.850 response codes to playback files.
  2. Enabling the announcement-on-error parameter on the realm-config or sip-interface of the caller. The same error-announcement-map applies to all realms and interfaces for which this parameter is enabled.

Note:

Transcoding based RBT and network announcements require transcoding resources. Be sure you have a transcoding core configured on your vSBCs to use this feature.

Additional Configuration Consideration

There are issues you may encounter with RBT generation with respect to compliance with RFC 6337, such as 1-way audio after the 200 OK. If the SDP presented in final 200 OK is not consistent with final 200 OK answer from the end station, this departure from RFC compliance may trigger a rejection of the SDP by the endstation. In such cases, the RBT may continue, but the call will fail.

To alleviate this compliance issue, set the unique-sdp-id option in the media-manager. 

ACMEPACKET(media-manager)# options +unique-sdp-id

If you type the option without the plus sign, you will overwrite any previously configured options. In order to append the new options to the realm configuration’s options list, you must prepend the new option with a plus sign as shown in the previous example.