AudioCodes Mediant 4000 SBC, User Manual

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CHAPTER 19 Coders and Profiles
Mediant 4000 SBC | User's Manual
Parameter Description
■ [0] RTP Mediation = (Default) Transcoding is done
only ifrequired. If not required, many of the media
settings (such as gain control) are not applied to the
voice stream. The device forwards the RTP packets
transparently (i.e., RTP-to-RTP) without processing the
data; only the RTP headers are re-constructed.
■ [1] Force Transcoding = Transcoding is always done
on the outgoing leg. The device interworks the media
for the SIP entity (as both legs have different media
capabilities), by implementing DSP transcoding. This
enables the device to receive capabilities that are not
negotiated between the SIP entities. For example, it
can enforce gain control to use voice transcoding even
though both legs have negotiated without the device's
intervention (such as Extension coders).
■ [2] RTP Forwarding = If transcoding is not required
and both legs are configured with RTP forwarding, then
RTP packets are forwarded transparently without any
processing. This mode is needed when the call parties
pass invalid RTP packets on the RTP port. If you use
this option, you may also need to configure the global
parameters 'Forward Unknown RTP Payload Types' to
Handle as Valid Packet , and 'Forward Invalid RTP
Packets' to Forward Packets .
Note:
■ To implement transcoding, you must configure the
number of required DSP channels for transcoding
(using the MediaChannels parameter). Each
transcoding session uses two DSP resources.
■ The corresponding global parameter is
TranscodingMode.
'Extension Coders Group'
sbc-ext-coders-group-
name
[IpProfile_
SBCExtensionCodersGroupNa
me]
Assigns a Coder Group for extension coders, which are
added to the SDP offer in the outgoing leg for the SIP entity
associated with the IP Profile. This is used when
transcoding is required between two IP entities (i.e., the
SDP answer from one doesn’t include any coder included
in the offer previously sent by the other).
For more information on extension coders and transcoding,
see
Coder Transcoding . To configure Coder Groups, see
Configuring Coder Groups .
'Allowed Audio Coders'
allowed-audio-coders-
group-name
[IpProfile_
SBCAllowedAudioCodersGroup
Name]
Assigns an Allowed Audio Coders Group, which defines
audio (voice) coders that can be used for the SIP entity
associated with the IP Profile.
To configure Allowed Audio Coders Groups, see
Configuring Allowed Audio Coder Groups . For a description
of the Allowed Coders feature, see Restricting Coders .
'Allowed Coders Mode' Defines the mode of the Allowed Coders feature for the SIP
entity associated with the IP Profile.
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