Polycom SIP 3.0.2 ユーザーズマニュアル

Administrator’s Guide SoundPoint IP / SoundStation IP 

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The phone employs a high-performance jitter buffer and packet error 

concealment system designed to mitigate packet inter-arrival jitter and 
out-of-order or lost (lost or excessively delayed by the network) packets. The 

jitter buffer is adaptive and configurable for different network environments. 
When packets are lost, a concealment algorithm minimizes the resulting 
negative audio consequences.
Configuration changes can performed centrally at the boot server or locally:

The purpose of voice activity detection (VAD) is to conserve network 
bandwidth by detecting periods of relative “silence” in the transmit data path 
and replacing that silence efficiently with special packets that indicate silence 
is occurring. For those compression algorithms without an inherent VAD 
function, such as G.711, the phone is compatible with the comprehensive 
codec-independent comfort noise transmission algorithm specified in RFC 
3389. This algorithm is derived from G.711 Appendix II, which defines a 
comfort noise (CN) payload format (or bit-stream) for G.711 use in 

packet-based, multimedia communication systems. The phone generates CN 
packets (also known as Silence Insertion Descriptor (SID) frames) and also 
decodes CN packets, efficiently regenerating a facsimile of the background 
noise at the remote end.
Configuration changes can performed centrally at the boot server:

Configuration file: 
sip.cfg

Set the jitter buffer tuning parameters including minimum and 

maximum size and shrink aggression.
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For more information, refer to 

 on 

page 

.

Web Server 
(if enabled)

Set the jitter buffer tuning parameters including minimum and 

maximum size and shrink aggression. 
Navigate to http://<phoneIPAddress>/coreConf.htm#au
Changes are saved to local flash and backed up to <Ethernet 
address>-phone.cfg

 on the boot server. Changes will permanently 

override global settings unless deleted through the Reset Local 

Config menu selection and the <Ethernet address>-phone.cfg is 

removed from the boot server.

Configuration file:  
sip.cfg

Enable or disable VAD and set the detection threshold. 
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For more information, refer to 

 on 

page 

.