AudioCodes Mediant 1000 User Manual page 620

Mediant 1000B Gateway & E-SBC
The figure below illustrates transcoding between two SIP entities (IP Groups) where one
uses G.711 (LAN IP phone) and the other G.729 (WAN IP phone). The initial SDP offer
received on the inbound leg from the LAN IP phone includes coder G.711 as the supported
coder. In the outgoing SDP offer on the outbound leg to the WAN IP phone, the device
adds extension coder G.729 to the SDP, which is supported by the WAN IP phone. The
subsequent incoming SDP answer from the WAN IP phone includes the G.729 coder as
the chosen coder. Since this coder was not included in the original incoming SDP offer
from the LAN IP phone, the device performs G.729-G.711 transcoding between the
inbound and outbound legs.
Figure 28-5: Transcoding using Extended Coders (Example)
User's Manual 620 Document #: LTRT-27045