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Videoconferencing Standards Protocol
H.261: ITU standard for video coding for videoconferencing. H.261 is a
discrete cosine transform (DCT) based algorithm for video in the 64kb/s to 2mb/s
range. All H.323 compliant video conferencing systems are required to support
this codec.
H.263: ITU standard for video coding within videoconferencing. H.263
offers better compression than H.261, particularly in the low bit rate range
used by modems.
H.320: Suite of standards for multimedia conferencing on narrowband
switched digital networks. Commonly used with ISDN service.
H.321: Suite of standards used for ATM narrowband conferencing. (See
narrowband)
H.323: Suite of standards for multimedia conferencing on traditional IP
networks.
VPN: Virtual Private Network. A virtual private network (VPN) is a way to
use a public telecommunication infrastructure, such as the Internet, to provide
remote offices or individual users with secure access to their organization's
network. Videoconferencing Terms
Bridge: In telecommunication networks, a bridge is a product that
connects a local area network (LAN) to another local area network that uses the
same protocol (for example, Ethernet or Token Ring). In Video conferencing, a
bridge is a product that connects an endpoint or codec to another endpoint or
codec that uses the different protocol or that is on a different network.
CIF: A video format that supports both NTSC and PAL signals. CIF is part
of the ITU H.261 videoconferencing standard. It specifies a data rate of 30
frames per second (fps), with each frame containing 288 lines and 352 pixels per
line.
Codec: Coder-Decoder. A device that "codes" analog signals into digital
bit streams for transmission over digital circuits then "decodes" the bits into
analog waves at the receiving end. A Codec in videoconferencing is usually the
users endpoint.
Continuous Presence: Videoconferencing that allows the participants to
see all of the other participants at the same time in the videoconference.
Echo suppression: Echo suppression is a crucial portion of video
conferencing. This avoids, the person speaking from hearing his own audio coming
back from the other end of the circuit, after a small time delay. The fault
always lies with the far end, as the sound from their speakers are going into
their microphone and being sent “back” to the person the audio came from. Echo
suppression avoids this problem.
LATA: Local Access Transport Areas. There are three LATAs in New Jersey
(Newark/Atlantic City/Mt. Laurel). Telecommunications services between LATA must
be provided by a Long Distance Carrier (Verizon is now a Long Distance carrier
in NJ).
Gatekeeper: A gatekeeper is an H.323 entity on a LAN that provides
address translation and control access to the LAN for H.323 terminals and
gateways. The gatekeeper can provide other services to the H.323 terminals and
gateways, such as bandwidth management and locating gateways. A gatekeeper
maintains a registry of devices in the multimedia network. The devices register
with the gatekeeper at startup and request admission to a call from the
gatekeeper.
Gateway: A gateway is a network point that acts as an entrance to another
network.
IMUX (Inverse Multiplexer): An inverse multiplexer combines multiple
network channels to one aggregate higher speed pipe for transmitting video or
data. It does this dynamically, to provide bandwidth on demand, in multiples of
56 or 64 Kbps. This functionality is used in video conferencing usually with
ISDN equipment to “mux” together ISDN digital lines for 384 K conferencing.
MCU: Multipoint Conference Unit, sometimes referred to as a "bridge."
Multicast: The ability to broadcast to one or many video end points.
Multipoint: A video communications connection between more than two sites
via a Multipoint Conference Unit (MCU) or bridge.
NT-1: Network Termination Adaptor. Used to terminate ISDN equipment to
Tele-Co digital phone lines.
Point-to-Point: Communication that takes place between two video sites.
QCIF: A standard related to CIF, QCIF (Quarter CIF), transfers one fourth
the amount of data and is suitable for videoconferencing systems on slower
connections or telephone lines.
QoS: Quality of service.
Video Broadcast: A one-way transmission of video. This video can be
transmitted to one end point on the LAN/WAN or to many endpoints.
Video Switching: Videoconference where endpoints are switched on
voice-activated audio so you see only participant speaking.
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