CHAPTER19 Coders and Profiles
Mediant 1000 Gateway & E-SBC | User's Manual
19 Coders and Profiles
This section describes configuration of coders and SIP profiles.
Configuring Coder Groups
The Coder Groups table lets you configure up to 11 Coder Groups. The Coder Group determines the
audio (voice) coders used for calls. Each Coder Group can include up to 10 coders, where the
packetization time (ptime), bit rate, payload type, and silence suppression can be configured per
coder. The first coder in the Coder Group has the highest priority and is used by the device
whenever possible. If the remote side cannot use the first coder, the device attempts to use the
next coder in the Coder Group, and so on.
The Coder Groups table provides a pre-defined Coder Group (index 0) that is configured with the
G.711 A-law coder. If no other Coder Groups are configured, the default Coder Group (which you
can modify) is used for all calls. Alternatively, if you want to use specific coders or coder settings
(e.g., packetization time) for different calls (entities), you need to configure a Coder Group for each
entity and then assign each Coder Group to a Tel Profile (see Configuring Tel Profiles) or an IP
Profile (see Configuring IP Profiles) associated with the entity (IP Group). If an IP Group is not
associated with a Coder Group, the default Coder Group is used.
You can also use Coder Groups for audio coder transcoding of SBC calls. If two SIP entities need
to communicate, but one does not support a coder required by the other, the device can add the
required coder to the SDP offer. The added coder is referred to as an extension coder. For more
information on extension coders, see Coder Transcoding.
To apply a Coder Group for transcoding to a SIP entity:
1. Configure a Coder Group in the Coder Groups table (see description below).
2. In the IP Profile associated with the SIP entity (see Configuring IP Profiles):
● Assign the Coder Group (using the IpProfile_SBCExtensionCodersGroupName
parameter).
● Enable the use of the Coder Group for transcoding (by configuring the IpProfile_
SBCAllowedCodersMode parameter to Restriction or Restriction and Preference).
● For supported audio coders, see Supported Audio Coders.
● Some coders are license-based and are available only if included in the License
Key installed on your device. For more information, contact the sales
representative of your purchased device.
● Only the packetization time of the first coder listed in the Coder Group is declared in
INVITE/200 OK SDP even if multiple coders are configured. The device always
uses the packetization time requested by the remote side for sending RTP
packets. If not specified, the packetization time is assigned the default value.
● The value of some fields is hard-coded according to common standards (e.g.,
payload type of G.711 U-law is always 0).
● The G.722 coder provides Packet Loss Concealment (PLC) capabilities, ensuring
higher voice quality.
● For more information on V.152 and implementation of T.38 and VBD coders, see
Supporting V.152 Implementation.
● The G.729 coder refers to G.729A if silence suppression is disabled, or G.729AB if
silence suppression is enabled.
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