Below are frequently used videoconferencing-related terms.
AES Encryption (Advanced Encryption Standard) Encryption. 128 bit encryption providing a high level of security, higher than 3DES, for organizations with sensitive security concerns.
Asynchronous Typical transmission method of dial-up modems. Data is transmitted using a start bit at the beginning of a character and a stop bit at the end. The time interval between characters may be of varying lengths. Synchronous data uses an external reference clock to unify both ends of the data circuit.
Analog Signal A type of signal that encodes voice, video, or data transmitted over wire or through the air, and is commonly represented as an oscillating wave. An analog signal can take any value in a range and changes smoothly between values, as opposed to digital signals, which is characterized by discrete bits of information in numerical steps. An analog signal can transmit analog or digital data.
ATM Asynchronous Transfer Mode. A high bandwidth, high speed (up to 155 Mbps), controlled-delay fixed-size packet switching and transmission system integrating multiple data types (voice, video, and data). Uses fixed-size packets also known as "cells" (ATM is often referred to as "cell relay").
Bandwidth Bandwidth is the data capacity of a service, measured in thousands of bits per second (kbps) or millions of bits per second (Mbps). In videoconferencing systems a larger bandwidth is used to spread or "dither" the signal in order to prevent interference.
Baseband The basic direct output signal in an intermediate frequency based obtained directly from a television camera, videoconference television receiver, or video tape recorder. Baseband signals can be viewed only on studio monitors. To display the baseband signal on a conventional television set a "modulator" is required to convert the baseband signal to one of the VHF or UHF television channels which the television set can be tuned to receive.
BRI Basic Rate Interface or BRI ISDN converts your regular telephone wires into three signaling channels. Two 64 kilobit per second (Kbps) Bearer (B) channels each carry user information (voice and data), while one 16Kbps Data (D) channel carries call set-up and signaling information, giving you a maximum capability of 144Kbps. The D Channel also enables X.25 packet applications such as credit card authorizations, automatic teller machine transactions and other short bursty messages that would needlessly tie up a connection over the regular circuit-switched network. The 2 B channels can be combined in one call for such applications as videoconferencing for a total of dedicated 128Kbps bandwidth. [Most high quality ISDN videoconferencing programs are done over 3 BRI lines for a total of 384Kbps].
Bridge In videoconferencing vernacular, a bridge connects three or more conference sites so that they can simultan-eously pass data, voice, or video. Videoconferencing bridges are often called MCU's or multipoint conferencing units.
Broadband A way of transmitting large amounts of data, voice, and video that is greater than telephony networks. In ISDN, broadband channels support rates above the primary rate (1.544 Mbps or 2.048 Mbps).
Cascading Cascading is a method of allowing the number of participants to expand beyond what a single MCU can support. Cascading allows one MCU videoconference to join or be invited into another MCU videoconference. The joining MCU videoconference becomes a participant of the videoconference it joins and is treated like the other participants. The host MCU sends the joining MCU the processed data streams, which the latter distributes to its videoconference participants. In this way, all of the participants in the expanded videoconference receive the same information.
Common Intermediate Format (CIF). An international standard for video display formats developed by TSS. The QCIF format, which employs half the CIF spatial resolution in both horizontal and vertical directions, is the mandatory H.261 format. QCIF is used for most desktop videocon-ferencing applications where head and shoulder pictures are sent from desk to desk.
Codec COder-DECoder. In the videoconferencing world, a video codec converts analog video signals from a video camera to digital signals for transmission over digital circuits, and then converts the digital signals back to analog signals for display.
Compression Compression is a technique that reduces the quantity of bandwidth or bits required to encode a block of information so that it occupies less space on a transmission channel or storage device and a fundamental concept of video communications.
Continuous Presence An optional view on the screen whereby all participants in the meeting are seen at the same time.
D-channel A channel that carries WAN synchronization information on a line using ISDN D-channel signaling.
Decoder A television set-top device which enables the home subscriber to convert an electronically scrambled television picture into a viewable signal. This should not be confused with a digital coder-decoder known as a codec which is used in conjunction with digital transmissions.
Duo Video Duo Video is a feature of TANDBERG videoconferencing systems for one, which allows the codec to send two live video streams simultaneously. This makes communicating easier by allowing a viewer to see the person speaking and the presentation, file or object that the person is speaking about, at the same time.
Fractional T-1 Service offering data rates between 64 kbps (DS0 rate) and 1.536 Mbps (DS1 rate), in specified intervals of 64 kbps. It is typically provided by a carrier in lieu of a full T-1 connection and is a point-to-point arrangement. A specialized multiplexer is used by the customer to channelize the carrier's signals.
FTP File Transfer Protocol. The Internet protocol (and program) used to transfer files between hosts.
Full-Duplex Audio 2-way audio simultaneously transmitted and received without any interference or "clipping." A common feature of room-based videoconferencing systems.
Full-Motion Video In the videoconferencing world, the term "full-motion video" is often used and misunderstood. Videoconferencing systems cannot provide 30 fps for all resolutions at all times nor is that rate always needed for a high-quality, satisfying video image. Picture quality must sometimes be sacrificed to achieve interactive visual communication economically. Videoconferencing vendors often use "full motion video" to refer to any system that isn't still-frame. Most videoconferencing systems today run 10 to 15 fps at 112 Kbps. Full motion video is equivalent to broadcast television video with a frame rate of 30 fps for NTSC signals or 25 fps for PAL signals. Images are sent in real time and motion is continuous. Also known as continuous-motion video.
Gateway Gateways are points of entrance to and exit from a communications network. Viewed as a physical entity, a gateway is that node which translates between two otherwise incompatible networks or network segments.
H.264 H.264 is an ITU standard describing protocols, services and equipment for multimedia communication over Internet protocols (IP). H.264 uses a compression algorithm that allows for higher data transfer speeds requiring only 384 Kbps, giving superior capture and display on low bandwidth.
H.320 H.320 is an ITU standard describing protocols, services and equipment for multimedia communication over ISDN, narrow-band visual telephone systems and terminal equipment. The standards cover three types of media: audio, video and data.
H.323 H.323 is an ITU standard describing protocols, services and equipment for multimedia communication over Internet protocols (IP). The standards cover three types of media: audio, video and data.
H.350 A relatively new video compression standard developed by the Internet2 Middleware Initiative Video Working Group and the Video Development Initiative (ViDE), that provides a "light directory access protocol" (LDAP) object class specification designed to store and locate information related to video and voice over Internet Protocol (VoIP) in enterprise directories. H.350 supports H.320, H.323, session initiation protocol (SIP), and non-standard protocols including IP addresses, aliases and other connection related details.
Hub A network’s or system’s signal distribution point where multiple circuits convene and are connected. Some type of switching or information transfer can then take place.
IP (Internet Protocol) Internet protocols are used to communicate across any set of interconnected networks. Internet protocols can be used to specify common applications such as electronic mail, terminal emulation, and file transfer. Internet protocols were first developed in the mid-1970s, when the Defense Advanced Research Projects Agency (DARPA) became interested in establishing a packet-switched network that would facilitate communication between dissimilar computer systems at research institutions.
ISDN Integrated Services Digital Network. An international standard for end-to-end digital transmission of voice, data, and signaling—providing simultaneous voice, video, and text transmission between individual desktop videoconferencing systems and group (room) videoconferencing systems.
Isochronous Pronounced “I-sockronous” Data transmission where timing is derived from the signal carrying the data. No timing or clock lead is provided at the customer interface. In Isynchronous data transmission, data has no embedded timing—send it slower and it is still valid, only late. Voice and video are intimately tied to timing. With TMD (Time Division Multiplexing) services, there is a direct relationship between the signal rate used to digitize the voice and samples and the bearer channel rate, allowing accurate reconstruction of the voice (or other signals) at the far end. In packet technol-ogies, no such relationship exists. Services like ATM must use care in transferring such signals so timing can be recovered since it cannot be derived from the ATM bearer channel.
LAN Local Area Network. Most LANs are confined to a single building or group of buildings and connect workstations, printers, and other devices. LAN's enable to access data and devices anywhere on the LAN so that users can share equipment and data. A system of connected LANs is called a wide-area network (WAN).
Leased Line A dedicated circuit typically supplied by the phone company.
Multiplexing The combination of two or more signals from two or more channels into a single output. For example, in ISDN, three BRI lines (6 channels) are normally used to create a single 384 kbps connection. This is the minimum standard speed for higher end videoconferencing. The multiple channels must be multiplexed or de-multiplexed with a Network Terminating (NT-1) device (see below). These are usually built-in to videoconferencing systems.
MCU Multipoint Control Unit (also called a bridge). TANDBERG Videoconferencing equipment that allows more than three individual videoconference units to connect together to form a multiparty videoconference session. The MCU uses fast switching techniques to patch the presenters or speaker's input to the output ports representing the other participants.
MultiSite The TANDBERG MultiSite feature on a videoconferencing system allows multiple participants from multiple sites to join in a meeting-by telephone or by video. When this feature is built-in to a vidconferencing system, there is no need to use an external bridge or bridging service.
Network A group of stations (computers, telephones, or other devices) connected by communications facilities for exchanging information. Connection can be permanent, via cable, or temporary, through telephone or other communications links.
Natural Presenter Package (NPP) The Natural Presenter Package (NPP) is a package of the most frequently used videoconferencing features. It is available only on TANDBERG videoconferencing systems, and consists of Duo Video, PC Presenter, PC SoftPresenter, and Digital Clarity. This software package provides users with the ability to communicate more effectively using powerful presentation and communication tools.
NT1 Single ISDN BRI network termination device for use with 128Kbps BRI circuits. Converts U-Interface that comes from the telephone company to a S/T-Interface to provide video conferencing systems access to BRI ISDN services.
NT3 Triple ISDN BRI network termination device for use with up to three 128Kbps BRI circuits. Converts U-Interface that comes from the telephone company to a S/T-Interface to provide videoconferencing systems access to BRI ISDN services.
NT4 Quad ISDN BRI network termination device for use with up to four 128Kbps BRI circuits. Converts U-Interface that comes from the telephone company to a S/T-Interface to provide videoconferencing systems access to BRI ISDN services.
PBX Private Branch Exchange. A telephone switch, usually located on a customer’s premises, connected to the telephone network but operated by the customer. A PBX provides pooled access to a given number of inside (extension) lines in a smaller number of outside lines (trunks). Ingoing and outgoing calls are handled by an operator or switched automatically by the PBX software.
PRI (Primary Rate Interface) A PRI circuit that provides (up to) 23 64kbps clear channels for voice, video or data and a single 64kbps channel for dialing.
Simultaneous Support for H.323/H.320 Embedded support for H323 and H320 means that the video-conferencing systems allows users to choose whether they wish to run videoconferencing over IP or over ISDN. Automatic IP/ISDN dialing ensures that the system will automatically detect whether it is an IP or ISDN call.
Streaming Streaming media technology allows real time or on demand delivery of audio, video and multimedia. Digital media (video, voice, data) is received in a simultaneous, continuous stream. These applications can start displaying video immediately or play as soon as enough data has been received and stored in the receiving station’s buffer.
Switched 56 A dial-up network-based service providing a data channel operating at a rate of 56 kbps. Also a type of network access line, used to provide access to switched 56 network services.
10Base-T Standard ethernet. A variant of IEEE 802.3 allowing stations to be attached via twisted pair cable.
T1 T-1 is a carrier signal for DS1 or PRI ISDN digital line services.
T.120 A standard for audiographics exchange. While H.320 does provide a basic means of graphics transfer, T.120 will support higher resolutions, pointing and annotation. Users can share and manipulate information much as they would employ if they were in the same room, though they are working over distance and using a PC platform. T.120 will allow audio bridge manufacturers to add graphics to their products in support of a wide range of applications.
T3 Channel (DS-3) In North America, a digital channel which communicates at 45.304 Mbps.
VNC Virtual Network Computing. A free software-based application allowing pc-based control over another network device.