CHAPTER19 Coders and Profiles
Mediant 4000 SBC | User's Manual
Configuring Various Codec Attributes
The following procedure describes how to configure various coder attributes such as bit rate.
➢ To configure codec attributes:
1. Open the Coder Settings page (Setup menu > Signaling & Media tab > Coders & Profiles
folder > Coder Settings).
2. Configure the following parameters:
● AMR coder:
◆ 'AMR Payload Format' (AmrOctetAlignedEnable): Defines the AMR payload format
type:
● SILK coder (Skype's default audio codec):
◆ '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.
● Opus coder:
◆ 'Opus Max Average Bitrate' (OpusMaxAverageBitRate): Defines the maximum
average bit rate (in bps) for the Opus coder.
3. Click Apply.
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. 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.
For example, assume the following:
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