Polycom Version 1.4.x 17 manual Local Conference Mixing, Voice Activity Detection VAD

Administrator Guide - SoundPoint® IP / SoundStation® IP Features

Central	Configuration file:	Set the jitter buffer tuning parameters including minimum
	ipmid.cfg	and maximum size and shrink aggression.
(boot
		• For more information, see 4.6.1.6.1.2 Codec Profiles
server)
		<profiles/> on page 79.
	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 per-
		manently override global settings unless deleted via the
		Reset User Settings menu selection.
	Local Phone User	None.
	Interface

3.3.3 Local Conference Mixing

The phone’s audio processing subsystem contains a flexible three-party conferencing

capability2. This feature can be used to set up local three-party conferences where no external protocol signaling is involved.

3.3.4 Voice Activity Detection (VAD)

The purpose of VAD is to conserve network bandwidth by detecting periods of rela- tive “silence” in the transmit data path and replacing that silence efficiently with spe- cial 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 com- fort noise (CN) payload format (or bit-stream) for G.711 use in packet-based, multi- media 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.

Central (boot server)

Configuration file: ipmid.cfg

Enable or disable VAD and set the detection threshold.

•For more information, see 4.6.1.6.10 Voice Activity Detection <VAD/> on page 86.

422. On SoundStation IP® 4000, Cconferencespyright © are2004notPolycom,availableIncif.the G.729 codec is enabled on the phone. This restriction will be removed in future releases.