Core Issue
Cisco Conference Connection only supports G711 u-law. Using any other codec requires the use of a transcoder.
Resolution
There are a number of methods for accessing the transcoding resource for Cisco Conference Connection. The most common is the Cisco Catalyst 6000 Family Voice T1 and E1 and services modules (product number WS-X6608).
For more information, refer to Cisco bug ID CSCdw28983.
Other devices include the Cisco Catalyst 4604 Access Gateway card or the Cisco VG200 Series Gateway with a Digital Signal Processor (DSP) populated card.
For more information, refer to these documents: