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Glossary of Video Conferencing Terms

Analog: An electrical signal that has a continuous nature rather than pulsed or discrete. An example is the traditional format in which multiplexed video and audio are transmitted using an RF carrier, modulated by changes in amplitude and phase induced by video and audio signals. See digital.

Aspect Ratio: The aspect ratio of an image is its displayed width divided by its height. The aspect ratio of a traditional television screen is 4:3, or 1.33:1. High-definition television and European digital television use an aspect of 16:9, or about 1.78:1. Aspect ratios of 2.39:1 or 1.85:1 are frequently used in cinematography, while the aspect ratio of a sync-sound 35 mm film frame is 1.37:1 (also known as "Academy Aperture" ratio).

Bandwidth: Determines the rate at which information can be transmitted across a medium. The rates are measured in bits (b/s), kilobits (Kb/s), megabits (Mb/s) or gigabits per second (Gb/s). Typical transmission services are 56Kb/s, 64Kb/s, 1.544Mb/s (T1) and 45Mb/s (T3), 10/100/1000Mb/s (Ethernet).

Bonding: Method for making several ISDN BRI lines look like one high-rate line by use of an IMUX (inverse multiplexer).

bps: Bits per second - A unit of measurement of the speed of data transmission and thus of bandwidth (lower case is significant).

BRI: Basic Rate Interface. An ISDN subscriber line, consisting of two 64Kb/s B channels (bearer channels) and one 16Kb/s D channel (used for signaling and synchronization purposes.) - often referred to as 2 B's and a D.

Bridge: An interconnection device that can connect LANs using similar or dissimilar media and signaling systems such as Ethernet, Token Ring and X.25. A bridge is also called a data link relay or level 2 relay. Connects remote sites over dedicated or switched lines to create WANs. Also the device that allows multiple locations (more than 2) to video conference simultaneously. Also sometimes called a MCU.

Codec: COder-DECoder. A video codec converts the analog video signals from a video source to digital signals for transmission over digital circuits, then converts the digital signals back to analog signals for display. An audio codec converts the audio signals to digital signals for transmission over digital circuits, then converts the digital signal back to analog for reproduction.

Compression: The method of taking raw data and processing it so that it may be represented with less information (or bits in the digital world.) Compression falls into two categories: lossless - the original data may be completely recovered - and lossy - the representation of the original data contains errors.

Compressed Video: Processed video images; transmits changes from one frame to the next which reduces the bandwidth to send them over a telecommunications channel which reduces cost. Also called bandwidth compression or bit rate reduction.

Concierge Services: A general term to describe the "white glove" or "high touch" services provided by outside firms to manage very high end video conference or telepresence rooms. All aspects of calls and reservations are handled by an operator, making an interface with and/or an understanding of the technology unnecessary.

Continuous Presence: Continuous Presence (CP) allows you to view multiple participants in one screen at the same time. Incoming participant images are combined into a video image layout set according to the policies of the conferencing service. The range of video layouts available depends on the type of media processing supported.

Control system: An integrated solution that allows the user to control audio, video, conferencing, computer, IP and environmental systems from a single interface, usually a touch screen or touch panel. Control systems can operate as simply as an on/off button or they can utilize intricate complexities, issuing a string of commands and executing multiple assignments automatically at the touch of a button.

CPE: Customer Premise Equipment. Terminal equipment located on the customer premises which connects to the telephone network.

CSU: Channel Service Unit. A device used to connect a digital phone line coming in from a carrier to network access equipment located on the customer premises. A CSU may also be built into the network interface of the network access equipment.

D Channel: The data signaling channel of an ISDN line. This channel is used to carry call control messages between the ISDN terminal and the public switch.

Delay: The time taken for a signal to pass through a video conference from the sending station to the receiving station.

DES: Data Encryption Standard. An algorithm for encrypting (coding) data designed by the National Bureau of Standards so it is impossible for anyone without the decryption key to get the data back in unscrambled form.

Desktop Video conferencing: Video conferencing on a personal computer - Most appropriate for individuals.

Digital: The transmission of discontinuous electrical signals containing information encoded in binary form that has only two possible states: 0 or 1. Digital signals have the distinct advantage over analog because they are easily transported and replicated without loss to the original. See also analog.

Directional Microphone: A microphone that detects and transmits sound from only a certain direction. Useful in preventing unwanted sound from being transmitted.

Display: The visual presentation on the indicating device of an instrument.

Distance Learning: Incorporation of video and audio technologies so that students can "attend" classes and training sessions presented at a remote location.

Document Sharing: A video conferencing feature that enables multiple participants to view and edit the same computer document.

Echo Canceller: Eliminates audio transmission echo. A telephone line echo canceller produces a synthetic replica of the echo it expects to see returning and subtracts it from the transmitted speech. The replica it creates is based on the transmission characteristics of the telephone cable between echo canceller and the telephone or video conferencing system. A device that allows for the isolation and filtering of unwanted signal caused by echoes from the main transmitted signal.

Electronic Whiteboard: A device or whiteboard that looks like an ordinary blackboard or whiteboard, but has a special conductive surface for producing free hand information that can be sent to a computer.

Endpoint: A network element at the end of the network such as an H.323 terminal, a Gateway, a Multipoint Controller Unit (MCU), a PC terminal, IP or ISDN phone, or video conference.

FCC: Federal Communications Commission. An independent US government agency charged with regulating interstate and international communications by radio, television, satellite and cable.

Firewall: A barrier device placed between two separate networks. A firewall can be implemented in a single router that filters out unwanted packets or it can use a variety of technologies in a combination of routers and hosts. Today many firewalls combine filtering functionality with Network Address Translations (NAT) functions.

fps: Frames per second (video).

Frame: Full screen or frame of video made up of two fields. Thirty frames is one second of video.

Frame Rate: The rate at which individual pictures (frames) in a sequence are displayed in a video conference. Frame rate is measured in frames per second (fps).

Frame Relay: Method for sending high-bandwidth data in frames (not video frames, but "blocks" of data). Uses packet switching, not circuit switching.

Full-duplex audio: Two-way audio may be captured and reproduced simultaneously. With full-duplex audio, the microphone may capture local audio for transmission while the far end audio may be heard clearly. Interruptions and double-talk are possible.

Full-motion Video: A standard video signal of thirty frames per second (fps).

Gateway: A router (or any computer) that performs protocol conversion between different types of networks or applications. For example, a gateway can convert a TCP/IP packet to a NetWare IPX packet and vice versa. Gateways perform complete conversions from one protocol to another rather than simply supporting one protocol from within another, such as IP tunneling.

H.261: A standard describing a protocol for digitally encoding and decoding video images to allow video conferencing terminals from different manufacturers to interoperate.

H.263: Video compression standard created under the ITU-T standards.

H.264: The ITU-T standard for compression that allows higher quality calls to pass over a lower bandwidth for advanced video coding in generic audiovisual services.

H.320: A set of CCITT standards describing a method of interoperability between video conferencing terminals from different manufacturers.

HDTV: Higher than normal definition TV. HDTV is generally defined as a system that offers double the horizontal and vertical resolutions up to 1080p compared to existing systems and provides compact disc quality sound.

IMUX: Inverse Multiplexer. A device that bonds two or more BRI lines to form a higher rate channel.

Instant Messaging (IM): A communications service that enables you to create a private chat room with another individual in order to communicate in real time over the Internet.

Inverse Multiplexing: The creation of a single higher speed data channel by combining and synchronizing two or more lower speed data channels.

IP: Internet Protocol. Packet-based protocol for delivering data across networks.

IP Address: The unique address of a computer attached to a TCP/IP network. IP addresses are 32 bits long. Each octet is represented in decimal and is separated by dots.

IP Multicast: A means of simultaneous transmission of data from a server to a group of selected users on a TCP/IP network, (internal, intranet or Internet). IP multicast is used for streaming audio and video over the network.

IP Network: A network that uses the TCP/IP protocol.

IP Telephony: A set of technologies that enables voice, data and video collaboration over existing IP-based LANS, WANs, and the Internet. IP technology uses open IETF and ITU standards to move multimedia traffic over any network that uses IP.

ISDN: Integrated Services Digital Network. A set of standards that provide a common architecture for the development and deployment of digitally integrated communications services. A set of standardized customer interfaces and signaling protocols for delivering digital circuit-switched voice / data / video and packet-switched data services.

ITU: International Telecommunications Union. Organization composed of the telecommunications administrations of the participating nations. Focus is the maintenance and extension of international cooperation for improving telecommunications development and applications.

Jitter: The result of a change in latency or the tendency towards lack of synchronization caused by mechanical or electrical changes. Technically, jitter is the phase shift of digital pulses over a transmission medium.

JPEG: Joint Photographic Expert Group. JPEG is an industry standard for still image compression that has moved into full motion video. JPEG is a compression technique based upon intraframe encoding technology. It allows for the full restoration of symmetrically compressed images.

LAN: Local Area Network. A private transmission network interconnecting offices within a building or a group of buildings used to convey voice, data and video traffic.

LAN/WAN Connectivity: The practical set of tools, from operating system layer protocols to support services that make a remote access device an effective link between LANs and WANs.

Latency: A measure of accumulated waiting time or delay, representing the length of time required for information to pass through a network.

Lavaliere: A small microphone that can be clipped onto clothing or suspended from neck cords and worn in front of the chest.

LCD: Liquid Crystal Display. A display technology that uses liquid crystal cells charged by electricity.

LEC: Local Exchange Carrier. Carriers that can carry only intra-LATA traffic. Local telephone companies such as Cincinnati Bell, Ohio Bell, Illinois Bell, Pacific Bell in California, etc.

LED: Light Emitting Diode. A display technology that uses a semiconductor diode that emits light when charged. LEDs usually indicate both correct and problematic operation.

Managed Services: An operational model where a firm hires a third party to coordinate their conferencing operations and or provide the related equipment.

Mbps: Megabits per second. A unit of measure of data of 1,000,000 bits per second.

MCU: Multipoint Controller Unit. Video conferencing equipment which allows multiple individual video conference units to connect together to form a multi-party video conference session.

MPEG: Motion Pictures Experts Group. Multimedia compression standard for professional and consumer applications such as digital video, digital audio and systems compression. MPEG compresses similar frames of video, tracks elements which change between frames and discards the redundant information.

MPEG-4: Moving Pictures Experts Group. MPEG is a series of standards designed to reduce the storage requirements of digital video. MPEG-4 provides the standardized technological elements for the integration of interactive graphics applications and interactive multimedia.

Multicast: Communication between a single sender and multiple receivers on a network. Useful for content delivery where a single stream is transmitted to multiple clients not connected to the server. The server sends one copy of the stream to multicast-enabled routers which replicate the data. Clients receive the stream by monitoring a specific multicast IP address and port.

Multiplexing: The process of combining a number of individual channels into a common frequency band or into a common bit stream for transmission. The converse equipment or process for separating a multiplexed stream into individual channels is called a demultiplexer.

Multipoint: A call involving three or more parties.

Multipoint Video conferencing: Video conference with more than two sites. The sites must connect via a video bridge. Also known as a MCU.

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 communication links. The transmission medium can be physical (fiber optic cable) or wireless (satellite).

PIP: Picture in Picture. A small video image is superimposed on a specified area of the monitor to allow the user to see two independent videos on a single monitor. PIP is often used in two-way video applications to allow the local user to monitor the video being sent along with the video being received.

Point to Point: A video conference between only two points.

Point to Multipoint: A video conference between one location to many.

Presence Based Collaboration: A general term used to describe PC based applications that indicate who in a workgroup is currently on-line and provide tools to communicate and share work.

PRI: Primary Rate Interface. An ISDN subscriber line, consisting of twenty three 64 Kb/s B bearer or user channels and one 64 Kb/s D channel, used for signaling and synchronization.

QoS: Quality of Service. Term for the set of parameters and their values which determine the performance of a given virtual circuit.

Router: A dedicated computer hardware and/or software package which manages the connection between two or more networks.

SIP: Session Initiation Protocol - An IP telephony signaling protocol developed by the IETF. SIP is a text-based protocol that is suitable for integrated voice-data applications. SIP is designed for voice transmission and uses fewer resources and is considerably less complex than H.323.

Streaming: A method of delivering digital media across a network in a continuous flow over networks and the Internet. The digital media is played by client software as it is received. Streaming files match the encoded bit rate to the connection speed of the user so the remote viewer can play audio or video with minimal stoppage without first downloading the entire video file.

Switched 56: A dial-up network-based service providing a data channel operating at a rate of 56Kb/s. Also a type of network access line, used to provided access to switched 56 network services.

Switched Network: Any network in which switching is present and is used to direct messages from the sender to the recipient. Usually, switching is accomplished by disconnecting and reconnecting lines in different configurations in order to set up a continuous pathway between the sender and the recipient.

T1: A digital transmission link with the capacity of 1.544Mb/s, used in North America. Typically channelized in 24 DSO's, each capable of carrying a single voice conversation or data stream. Uses two pairs of twisted pair wires.

T.120 Data Standard: Data sharing protocol for multipoint data communication in a multimedia conferencing environment. T.120 enables white board collaborations, file transfers, graphic presentations and application between participants in a conference.

TCP: Transmission Control Protocol. The protocol within TCP/IP that governs the breakup of data messages into packets to be sent via IP, and the reassembly and verification of the complete messages from packets received by IP.

Telco: Generic name for telephone companies.

Telecommunications: Communicating over a distance. Use of wire, radio, optical or other electromagnetic channels to transmit and receive signals for voice, data and video communications.

Telepresence: A video conferencing system or room that gives one the feeling that the remote participants are in the same room, usually involving high end equipment, systems and or dedicated networks.

Touch panel: A video screen that shows buttons, sliders and other controls that one can touch and interact with to adjust. Amongst its other many uses, it is often used as the main device to interact with control systems.

Transcoding: Audio/Video transcoding is the conversion of one audio/video transmission format into another.

Unicast: A method used by media servers for providing content to connected clients in which each client receives a discrete stream. No other client has access to that stream.

Unified (insert your choice - Desktop, Video, Collaboration, Communications): a new group of industry buzz-words used to describe an imagined panacea where all of the collaborative communication tools one could imagine will exist on a PC or other platform and work seamlessly with each other. An example would be an IM chat turning into a telephone call then a video call with data collaboration, with parties joining and adding from any location as they see fit.

VCS: Video Conferencing System.

Video Bridge: Computerized switching system which allows multipoint video conferencing. Also known as a MCU

Video conferencing: The use of digital video transmission systems to communicate between sites using video and voice. Digital video transmission systems typically consist of camera, codec, network access equipment, video and audio system.

Video on Demand Streaming: Delivery of a Video on Demand stream to a viewer upon request at any given time. Contrast this to a real-time stream that is delivered when the conference is in progress.

Voice Switched Video: Type of video conference in which the cameras are activated by voice signals to send a picture of a particular person in the group. Not all participants are seen at any one time in contrast to continuous presence video. Also known as Voice-Activated Video Switching.

VOIP: Voice over IP -See IP telephony.

VPN: Virtual Private Network - VPN modules create closed secure tunnels for communication between two firewalled LANs. VPN technology is one of the approached being used today for providing secure communications over IP networks.

VTC: Video Teleconferencing. An alternative name for videoconfrnecing.

VTR - VCR: Video Tape Recorder or Video Cassette Recorder. Equipment capable of recording or playing back pre-recorded video.

WAN: Wide Area Network. A data network typically extending a LAN outside a building or beyond a campus, over IXC or LEC lines to link other LAN's at remote sites. Typically created by using bridges or routers to connect geographically separated LANs.

Webcam: A video camera whose output may be viewed in real time over a network, especially over the Internet. Often used for remote monitoring.

Web Conferencing: Enables two or more logged in users to set up a typed, real-time, online conversation across the World Wide Web.

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