How can an administrator determine which codec is being used between two endpoints while a
call is in progress?

A.
Run the codec trace in Cisco Unified Communication Manager.

B.
Use Cisco Unified Serviceability network trace.

C.
Can only be seen in Cisco SDI traces.

D.
Can only be seen in a sniffer trace.

E.
Press the ? button twice on one of the IP phones.

Explanation:
pressing the button (?) twice in quick succession during an active call. The display
shows you receive and transmit statistics for the call
Link: http://docwiki.cisco.com/wiki/Cisco_Unified_Communications_–_One-Way_Audio