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Spectralink 84-Series Series Wireless Telephones Administration Guide
1725-86984-000_P.docx
September 2016
264
Reason for Null setting
The reg.1.server.1.port, reg.1.server.2.port, reg.1.server.1.transport, and
reg.1.server.2.transport values in this example are set to null to force NAPTR lookups.
Voice Activity Detection
The purpose of voice activity detection (VAD) is to detect periods of silence in the transmit data
path so the handset
doesn’t have to transmit unnecessary data packets for outgoing audio. This
process conserves network bandwidth. VAD must be turned on in the PBX for it to work
properly.
For compression algorithms without an inherent VAD function, such as G.711, the handset 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
handset 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.
These settings control the performance of the voice activity detection (silence suppression)
feature.
Table 11-12: Voice Activity Detection (VAD) Parameters
Parameter
Permitted Values
Default
voice.vad.signalAnnexB
1
0 or 1
1
If 0, there is no change to SDP. If 1, Annex B is used and a new line is added to SDP depending on the setting of
voice.vadEnable
.
If
voice.vadEnable
is set to 1, add parameter line
a=fmtp:18 annexb="yes"
below
a=rtpmap
…
parameter line (where '18' could be replaced by another payload).
If
voice.vadEnable
is set to 0, add parameter line
a=fmtp:18 annexb="no"
below
a=rtpmap
…
parameter line (where '18' could be replaced by another payload).
voice.vadEnable
1
0 or 1
0
If 0, voice activity detection (VAD) is disabled. If 1, VAD is enabled.
voice.vadThresh
1
integer from 0 to 30
15
The threshold for determining what is active voice and what is background noise in dB. Sounds louder than this
value will be considered active voice, and sounds quieter than this threshold will be considered background noise.
This does not apply to G.729AB codec operation which has its own built-in VAD function.
1
Change causes handset to restart or reboot.