Polycom 1725-11530-200 Rev A1 manual Voice Activity Detection

Administrator’s Guide - SoundPoint® IP / SoundStation® IP Features

urable for different network environments. When packets are lost, a concealment algo- rithm minimizes the resulting negative audio consequences.

Central	Configuration file:	Set the jitter buffer tuning parameters including minimum
	sip.cfg	and maximum size and shrink aggression.
(boot
		• For more information, refer to 4.6.1.8.1.2 Codec Pro-
server)
		files <profiles/> on page 109.
	Web Server	Set the jitter buffer tuning parameters including minimum
	(if enabled)	and maximum size and shrink aggression.
		Navigate to: http://<phoneIPAddress>/coreConf.htm#au
Local		Changes are saved to local flash and backed up to <Ethernet
		address>-phone.cfg on the boot server. Changes will perma-
		nently override global settings unless deleted through the
		Reset Local Config menu selection.
	Local Phone User	None.
	Interface

3.3.3 Voice Activity Detection

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 pack- ets, efficiently regenerating a facsimile of the background noise at the remote end.

Central	Configuration file:	Enable or disable VAD and set the detection threshold.
(boot	sip.cfg	• For more information, refer to 4.6.1.8.10 Voice Activity
server)
		Detection <VAD/> on page 118.
	Web Server	None.
Local	(if enabled)
	Local Phone User	None.
	Interface

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