Mitel 6867i Administrator's Manual page 240

Mitel 6800 Series SIP Phone Release 4.2.0 Administrator Guide
CUSTOMIZED CODEC PREFERENCE LIST
You can also configure the IP phones to use preferred codecs. To do this, you must enter the
payload value (payload), the packetization time in milliseconds (ptime), and enable or disable
silence suppression (silsupp).
Payload is the codec type to be used. This represents the data format carried within the RTP
packets to the end user at the destination. The default payload setting is to allow all codecs.
You can set payload to use only basic codecs (G.711 u-Law, G.711 a-Law, G.729), and/or
Adaptive Multi-Rate (AMR) and Adaptive Multi-Rate Wideband (AMR -WB) (G.722.2) codecs
(if a license is available), or select from up to 14 codecs for the phones AND customize a codec
preference list of up to 10 codecs. In the Mitel Web UI, codecs 2 through 10 can be set to "None"
if required (no codecs).
Note: In the Mitel Web UI:
• Setting Codec 1 to "All" ignores the packetization interval (ptime). The packetization
interval setting defaults to 30, which is the default for all codecs.
• Setting Codec 1 to "All" automatically sets all other codec preference fields 2 through
10 to "None".
• Setting Codec 1 to "Basic" and all other codec preferences in 2 through 10 to "None",
forces the phone to use only the basic codecs as in previous releases (G.711 u-law,
G.711 a-law, and G.729). If you select an additional codec to use in the codec pref-
erences 2 through 10 fields, those codecs are added to the list of Basic codecs for
the phone to use.
Ptime (packetization time) is a measurement of the duration of PCM data within each RTP
packet sent to the destination, and hence defines how much network bandwidth is used for
transfer of the RTP stream. You enter the ptime values for the customized codec list in
milliseconds. (See table below).
Silsupp is used to enable or disable silence suppression. Voice Activity Detection (VAD) on
the IP phones is used to determine whether each individual packet contains useful speech
data. Enabling silsupp results in decreased network bandwidth, by avoiding the transmission
of RTP packets for any frame where no voice energy was detected by the VAD.
You must enter the values for this feature in list form as shown in the following example:
payload=8;ptime=10;silsupp=on,payload=0;ptime=10;silsupp=off
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