AudioCodes Mediant 1000B User Manual page 601

User's Manual
•
The device does not add extension coders that also appear in the original SDP
offer.
As an example for using allowed and extension coders, assume the following:

Inbound leg:
•
Incoming SDP offer includes the G.729, G.711, and G.723 coders.
m=audio 6050 RTP/AVP 18 0 8 4 96
a=rtpmap:18 G729/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:4 G723/8000
a=fmtp:4 annexa=no
a=rtpmap:96 telephone-event/8000
a=fmtp:96 0-15
a=ptime:20
a=sendrecv
The SDP "m=audio 6010 RTP/AVP 18 0 8 4 96" line shows the coder priority,
where "18" (G.729) is highest and "4" (G.723) is lowest.
•
Allowed Audio Coders Group for coder restriction includes the G.711 and G.729
coders (listed in order of appearance).

Outbound leg:
•
Allowed Audio Coders Group for coder restriction includes the G.723, G.726, and
G.729 coders (listed in order of appearance).
•
Allowed Audio Coders Group for coder extension (transcoding) includes the
G.726 coder.
1. On the inbound leg for the incoming SDP offer: The device allows and keeps the
coders in the SDP that also appear in the Allowed Audio Coders Group for coder
restriction (i.e., G.711 and G.729). It changes the order of listed coders in the SDP so
that G.711 is listed first. The device removes the coders (i.e., G.723) from the SDP
that do not appear in the Allowed Audio Coders Group for coder restriction.
m=audio 6050 RTP/AVP 0 8 18 96
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:18 G729/8000
a=fmtp:4 annexa=no
a=rtpmap:96 telephone-event/8000
a=fmtp:96 0-15
a=ptime:20
a=sendrecv
2. On the outbound leg for the outgoing SDP offer: The SDP offer now includes only the
G.711 and G.729 coders due to the coder restriction process on the incoming SDP
offer (see Step 1).
a. The device adds the extension coder to the SDP offer and therefore, the SDP
offer now includes the G.711, G.729 and G.726 coders.
m=audio 6050 RTP/AVP 0 8 18 96 96
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:18 G729/8000
a=rtpmap:96 G726-32/8000
a=fmtp:4 annexa=no
a=rtpmap:96 telephone-event/8000
Version 7.0 601 Mediant 1000B Gateway and E- SBC
28. SBC Overview