Configuring Allowed Audio Coder Groups - AudioCodes Mediant 4000 SBC User Manual

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SILK coder (Skype's default audio codec):
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Opus coder:
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3. Click Apply.
20.2

Configuring Allowed Audio Coder Groups

The Allowed Audio Coders Groups table lets you configure up to 20 Allowed Audio Coders
Groups. For each Allowed Audio Coders Group, you can configure up to 10 audio coders.
The coders can include pre-defined coders and user-defined (string) coders for non-
standard or unknown coders.
Allowed Audio Coders Groups restrict coders for SIP entities. Only coders listed in the
Allowed Audio Coders Group (i.e., allowed coders) that is associated with the SIP entity
can be used. If the coders in the SDP offer ('a=rtpmap' field) of the incoming SIP message
are not listed in the Allowed Audio Coders Group, the device rejects the calls, unless
transcoding is configured, whereby "extension" coders are added to the SDP, as described
in Coder Transcoding on page 465. If the SDP offer contains some coders that are listed in
the Allowed Audio Coders Group, the device manipulates the SDP offer by removing the
coders that are not listed in the Allowed Audio Coders Group, before routing the SIP
message to its destination. Thus, only coders that are common between the coders in the
SDP offer and the coders in the Allowed Audio Coders Group are used. For more
information on coder restriction, see ''Restricting Audio Coders'' on page 464.
For example, assume the following:

The SDP offer in the incoming SIP message contains the G.729, G.711, and G.723
coders.
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The allowed coders configured for the SIP entity include G.711 and G.729.
The device removes the G.723 coder from the SDP offer, re-orders the coder list so that
G.711 is listed first, and sends the SIP message containing only the G.711 and G.729
coders in the SDP.
To apply an Allowed Audio Coders Group for restricting coders to a SIP entity:
1. Configure an Allowed Audio Coders Group in the Allowed Audio Coders Groups table
(see description below).
2. In the IP Profile associated with the SIP entity (see ''Configuring IP Profiles'' on page
418):
User's Manual
'Silk Tx Inband FEC': Enables forward error correction (FEC) for the SILK
coder.
'Silk Max Average Bit Rate': Defines the maximum average bit rate for the
SILK coder.
Figure 20-2: Configuring SILK Coder Attributes
'Opus Max Average Bitrate' (OpusMaxAverageBitRate): Defines the
maximum average bit rate (in bps) for the Opus coder.
Figure 20-3: Configuring Opus Coder Attributes
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Mediant 4000 SBC
Document #: LTRT-40203