Polycom VSX 7000
Product Reference Guide
October, 2003
4.4. Echo Cancellation, Automatic Noise Suppression and Gain Control
In addition to providing industry-leading technology for audio compression, VSX also delivers several audio
enhancement technologies that truly help to simulate the experience of being in the same room with the far end.
These technologies include:
IDEC
With Integrated Dynamic Echo Cancellation (IDEC), true full-duplex audio is provided, so that interruptions and
doubletalk are possible without any of the echo and cutoffs heard on typical speakerphones and
videoconferencing products.
IDEC continually updates its model of the room environment
, so if the microphone
moves or the room is reconfigured, IDEC will quickly adapt and continue to offer full-duplex audio.
ANS
Automatic Noise Suppression is a technique that reduces the noise level found within the audio channel. The
ANS algorithm can detect the difference between a true audio signal (such as speech) and the background noise
caused by vents, fans, etc. Using the noise model that it constructs for these sources, ANS is able to eliminate
the noise even when speech is present. ANS can produce virtually noiseless audio for most meeting
environments.
AGC
Automatic Gain Control is another algorithm that greatly enhances the audio pickup system of VSX 7000
systems. AGC intelligently normalizes speaking volumes so that persons seated further away from the
microphone sound as loud as those seated close to the microphone. By using sophisticated intelligence, AGC
will keep the volume of a whisper low enough to stop it from being accidentally picked up by the far end, and will
allow a loud speaker to sound as forceful as desired to get his or her point across.
4.5. Far-end Camera Control
Far end camera control is provided via the graphical user interface and in the remote controls. Different
technology is used depending on the network communication protocol:
•
In H.320 calls (ISDN and V.35), the system uses the H.281 protocol for far-end control. H.281 uses a low
speed data channel (under H.224) for the transmission of camera commands.
•
In H.323 calls (IP), the system uses H.323 Annex Q whenever the far-end supports it. If the far-end does
not support Annex Q, the system will use a modified version of the standard which is compatible with the
ViewStation, ViaVideo and (in limited) cases other manufacturers’ product lines.
5. Systems
Management
Two types of management can be combined in any given environment:
•
Browser-based – through WebRemote an administrator can have access to any system on the network simply
via a web browser.
•
Polycom Global Management System – allows administrators to manage their videoconferencing deployment
with a leading edge management tool.
Polycom Confidential
Subject to change without notice
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