Nortel Networks NN44470-100 - Manual (Page 19)

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MAS commissioning
Nortel Media Application Server 6.0 for AS 5300
Fundamentals
NN44470-100 01.01 Standard
Release 6.0 03 June 2008
Copyright © 2008, Nortel Networks
SIP registrar servers
A SIP registrar server is a database that contains the location of all user
agents within a domain. MAS registers its applications with all configured SIP
registrars. Registration is optional based on MAS configuration. Digest
authentication is supported.
Media conferencing
MAS supports multimedia conferencing for both audio and video streams. You
can use one of the following conferencing algorithms: basic and premium.
Basic conferencing algorithm
The basic conferencing algorithm mixes the two audio streams with the
highest energy and provides the mixed audio to the remaining participants.
The two participants with the highest energy audio streams receive only the
other active participant's audio so they do not hear themselves. The
participant with the highest energy with of the two highest energy speakers is
known as the primary active speaker. The other participant is the secondary
active speaker. (The system continually monitors the energy of all participants
in a conference, and using threshold algorithms, changes the conference
focus point.)
When some or all of the participants in the conference have corresponding
video streams, the video streams of the primary active speaker are replicated
and sent to those participants. The primary and secondary speakers see only
each other if they have video-enabled clients. The system attempts to provide
video participants with video when possible. If the active speaker does not
have video capabilities, participants receive a configurable replacement video,
which by default is an icon of a megaphone.
Premium conferencing algorithm
A more advanced conferencing algorithm (called premium conferencing)
mixes up to four parties simultaneously. Each channel runs a voice activity
detector (to determine speech versus background noise), an automatic gain
control algorithm, and a dynamic jitter buffer with compaction and packet loss
concealment. This algorithm is suitable for mixing large conferences.
Number of conferences and participants
MAS has no hard limitations on how many simultaneous conferences can
exist on the system, or how many participants can be in each conference. The
maximum number of participants in a single conference, without bridging
multiple conferences together, is limited only by the capacity of the scaled
system, which can vary based on hardware and the operating system.