Avaya Nortel Communication Server 1000 Manual page 216

216 Codecs
When the Call Server sets up a Call Server connection between an IP
Phone-to-IP Phone or IP Phone-to-Voice Gateway Channel Server, the
predefined table determines which codec it selects for that connection. This
information is provided to the system as part of the IP Phone registration
sequence.
For more information about the registration sequence, see Converging the
Data Network with VoIP Fundamentals (NN43001-260).
Codec selection
The systems use this information to set up a speech path and select a
codec that both endpoints support. As part of zone management, the
system further selects the codec based on whether it is trying to optimize
quality (BQ) or bandwidth usage (BB).
Codec refers to the voice coding and compression algorithm used by the
DSPs on the Voice Gateway Media Card. Different codecs provide different
levels of voice quality and compression properties. The specific codecs,
and the order in which they are used, are configured in the LTPS and on
the system.
Table 67 "Supported codecs" (page 216)
on the CS 1000 system.
The G.723.1 codec has bit rates of 5.3 kb/s and 6.3 kb/s. The G.723.1 codec can
only be configured with a 5.3 kb/s bit rate; however, the system accepts both
G.723.1 5.3 kb/s and 6.3 kb/s from the far end.
T.38 is the preferred codec type for fax calls over virtual trunks. However, the
G.711 Clear Channel codec is used if the far end does not support the T.38 codec.
Table 67
Supported codecs
Codec
G.711 a-law, G.711 mu-law, NOVAD
Copyright © 2003–2008, Nortel Networks
.
CAUTION
When voice compression codecs are used, voice quality is
impaired if end-to-end calls include multiple compressions.
ATTENTION
ATTENTION
Payload size
10, 20, and 30 ms
Nortel Communication Server 1000
IP Line Fundamentals
NN43100-500 02.02 Standard
Release 5.5 4 February 2008
shows which codecs are supported