Polycom CX5500 Unified Conference Station Administrator’s Guide 1.1.0
Polycom, Inc. 168
Example Configuration
The following example configuration illustrates how to add a custom sound effect from a sampled audio
file. In the example, the custom audio files MyTone.wav and Chirp.wav have been added as sound
effects 12 and 13. The welcome sound has been customized to use the sampled audio file 13
(Chirp.wav) with the label Birds. Ringtone 19 is named Whistle and is configured to use sampled audio
file 12 (MyTone.wav).
Voice Activity Detection
The purpose of voice activity detection is to detect periods of silence in the transmit data path so the
phone doesn’t have to transmit unnecessary data packets for outgoing audio. This process conserves
network bandwidth. The VAD parameters in the table Voice Activity Detection (VAD) will help you set up
this feature. For compression algorithms without an inherent VAD function, such as G.711, the phone
uses the codec-independent comfort noise transmission processing specified in RFC 3389. The RFC
3389 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, to
efficiently regenerate a facsimile of the background noise at the remote end.
Voice Activity Detection (VAD)
Central Provisioning Server
Specify if G.729 Annex B should be signaled
site.cfg > voice.vad.signalAnnexB
Enable or disable voice activity detection
site.cfg > voice.vadEnable
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