Audio Configuration - Cisco 521SG - Unified IP Phone VoIP Administration Manual

Cisco SPA IP Phone Field Reference
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Cisco Small Business SPA300 Series, SPA500 Series, and WIP310 IP Phone Administration Guide

Audio Configuration

A codec resource is considered as allocated if it has been included in the SDP
codec list of an active call, even though it eventually might not be the one chosen
for the connection. So, if the G.729a codec is enabled and included in the codec
list, that resource is tied up until the end of the call whether or not the call actually
uses G.729a. If the G.729a resource is already allocated and since only one
G.729a resource is allowed per device, no other low-bit-rate codec might be
allocated for subsequent calls; the only choices are G711a and G711u. On the
other hand, two G.723. 1 /G.726 resources are available per device.
Therefore it is important to disable the use of G.729a in order to guarantee the
support of two simultaneous uses of the G.723/G.726 codecs.
Parameter
Preferred Codec
Use Pref Codec Only
Second Preferred
Codec
Description
Preferred codec for all calls. (The actual codec used in
a call still depends on the outcome of the codec
negotiation protocol.) Select one of the following:
G711u, G711a, G722, G726-16, G726-24, G726-32,
G726-40, G729a, or G723.
Cisco SPA525G or Cisco SPA525G2: G711u, G711a,
G726-32, G729a, and G722. G.723 (not available on
Cisco SPA300 Series or Cisco SPA500 Series). G722
not available on Cisco WIP310.
Defaults to G711u.
To use only the preferred codec for all calls, select yes.
(The call fails if the far end does not support this
codec.) Otherwise, select no.
Defaults to no.
The second preferred codec when the preferred
codec cannot be used. If
enabled (set to yes), this parameter is not used.
Defaults to Unspecified.
Use Pref Codec Only i
A
s
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