A simple guide to videoconferencing and associated terms

A

Audio Bridge
A device used in audioconferencing that connects multiple telephone lines.

Audioconferencing
Voice only connection of more than two sites using standard telephone lines.

B

Bandwidth
In casual use, the amount of information that can be transmitted in an information channel. High bandwidth Internet access means those web graphics load quickly on Netscape. High bandwidth videoconferencing means that the picture and the sound will be clear. In computers, the speed at which data can be transmitted on a communications frequency. In telecommunication, the maximum frequency (spectrum) measured in Hertz or cycles per second, between the two limiting frequencies of a channel.

Basic Rate Interface (BRI)
Three digital signals over a pair of copper wires, 2 voice (B) channels and 1 signal (D) channel. For example, voice and fax on a single pair of wires.

Broadband
A high-capacity communications circuit/path. It usually implies a speed greater than 1.544 Mbps. (Contrast with wideband and narrowband).

C

Carbon Footprint
A term used to describe an individual or groups annual carbon emissions. For more information visit Go Green, Go Videoconferencing!

Certified Firewalls
Since H.323-compliant applications use dynamically allocated sockets for audio, video and data channels, a firewall must be able to allow H.323 traffic through on an intelligent basis. The firewall must be either H.323-enabled with an H.323 proxy, or able to “snoop” to control channel to determine which dynamic sockets are in use for H.323 sessions, and allow traffic as long as the control channel is active. Both the Cisco PIX Firewall and Checkpoint Firewall-1 firewalls feature Set allow H.323 traffic through on an as-needed basis by “snooping” the control channel.

CODEC
An acronym for COder/DECoder. In short, a codec is a piece of hardware or software that takes some signal (such as video or audio) and converts it to a format suitable for transportation using a specific set of protocols. Equipment on the receiving end must also use these same protocols. The H.323 standard is a collection of protocols designed to ensure compatibility between products of various manufacturers. Even though the term “codec” specifically refers to the hardware or software converter, the term has come to include the entire set of video conferencing terminal equipment. Someone saying “codec” is most likely referring to a set of terminal equipment. The terms “video conferencing terminal” and “codec” are used interchangeably.

CODEC ID
This name can be descriptive such as a room name, BL-123, a location, Accounting Dept., or a person’s name.

Camera presets
Allows pre-defined camera angles to be programmed into a videoconferencing system.

Cisco Systems
Global giant of network infrastructure and applications. Direct Visual is the only Cisco Select Partner in the videoconferencing industry.

Codec
Coder-Decoder. Videoconferencing hardware that codes the outgoing video and audio signals and decodes the incoming signals. Prior to transmission, the codec converts analogue-signals to digital signals and compresses the digital signals. Incoming audio and video must be decompressed and converted from digital back to analogue.

Codian
Now a member of the TANDBERG group, Codian is a groundbreaking videoconferencing infrastructure company, the highlight of their portfolio being a selection of cutting edge MCUs.

Compressed video
When the vast amount of information in a normal tv transmission is squeezed into a fraction of its former bandwidth by a codec, the resulting compressed video can be transmitted more economically over a smaller carrier. Some information is sacrificed in the process, which may result in diminished picture and sound quality.

D

DNS Name
The domain name system (DNS) is the way that Internet domain names are located and translated into Internet Protocol addresses. A domain name is a meaningful and easy-to-remember “handle” for an Internet address.

Desktop videoconferencing
Videoconferencing on a personal computer. Most appropriate for small groups or individuals (compare with room-based videoconferencing). Many desktop videoconferencing systems support document sharing.

Distance Education
The process of providing instruction when students and instructors are separated by physical distance, and technology, often in tandem with face to face communication.

Distance Learning
The incorporation of video and audio technologies into the educational process so that students can attend classes and training sessions in a location distant from that where the course is being presented. Distance learning systems are usually interactive an becoming a highly valuable tool in the delivery of education to widely dispersed students.

Document sharing
A feature supported by many desktop videoconferencing systems that allows participants at both ends of a videoconference to view and edit the same computer document.

Document Camera
The distance learning equivalent of an overhead projector. Images of two or three dimensional objects using either top or base lighting can be transmitted to remote sites when this video source is selected.

E

Echo-cancellation
Process of eliminating acoustic echo in a videoconferencing room.

F

Firewall
A firewall is a set of related programs, located at a network gateway server, that protects the resources of a private network from users from other networks. (The term also implies the security policy that is used with the programs.) An enterprise with an intranet that allows its workers access to the wider Internet installs a firewall to prevent outsiders from accessing its own private data resources and for controlling what outside resources its own users have access to.

Full Duplex
Sending data in both directions simultaneously “bidirectional” with a higher quality. In video conferencing, full duplex will be much more natural and useable. Cheap speakerphones are half duplex, whereas more expensive ones are full duplex.

FCIF/QCIF
Standards-based formats for communicating between videoconferencing systems from different vendors. QCIF is one quarter of the resolution of FCIF.

Frame Rate
Frequency in which video frames are displayed on a monitor, typically described in frames-per-second (fps). Higher frame rates improve the appearance of video motion. Broadcast TV (full motion video) is 30 frames-per-second.

Full Duplex Audio
2-way audio simultaneously transmitted and received without any interference or "clipping." A common feature of room-based videoconferencing systems. Contrast with half duplex audio.

Full motion video
Full motion video is equivalent to broadcast television video with a frame rate of 30fps. Images are sent in real time and motion is continuous.

G

Gatekeeper
The gatekeeper is the brain of an H.323 network, performing essential control, administrative, and managerial functions. However, the gatekeeper does not route any data packets in a network. These continue to rely on standard network routing equipment. The primary purposes of a gatekeeper are address translation and zone administration using layer three of the OSI model.

Gateway
A gateway is a network point that acts as an entrance to another network. On the Internet, a node or stopping point can be either a gateway node or a host (end-point) node. Both the computers of Internet users and the computers that serve pages to users are host nodes. The computers that control traffic within your company’s network or at your local Internet service provider (ISP) are gateway nodes. Can transcode or allow different protocols to talk to each other.

Global Leap
An organisation set-up to provide Schools, Colleges and Universities with help setting up videoconferences around the world. They also help promote virtual field trip and Distance Learning providers.

H

H.320
The ITU standard for video conferencing over digital networks such as ISDN.

H.321
The ITU standard for adaptation of H.320 video conferencing over digital networks such as B-ISDN.

H.323
The ITU standard for video conferencing over packet switched networks such as LANs and the Internet.

H.323 ID
This name can be descriptive such as a room name, BL-123, a location, Accounting Dept., or a person’s name.

Half-Duplex
Transfers data in both directions, but not simultaneously. Normal operation is alternate, one-way-at-a-time transmission.

Hub
Hub is a place of convergence where data arrives from one or more directions and is forwarded out in one or more other directions.

H.323 standard
The H.323 protocol is the International Telecommunications Union - Telecommunications (ITU-T) standard for real-time multimedia communications and conferencing over packet-based networks.

I

IP address
The IP address is usually expressed as four decimal numbers, each representing eight bits, separated by periods. This is sometimes known as the dot address and, more technically, as dotted quad notation. For Class A IP addresses, the numbers would represent “network.local.local.local”; for a Class C IP address, they would represent “network.network.network.local.” The number version of the IP address can (and usually is) represented by a name or series of names called the domain name.

ISDN
Stands for Integrated Services Digital Network. ISDN is essentially a digital network that will provide seamless communications of voice, video, and text between individual desktop videoconferencing systems and group videoconferencing systems. ISDN is expected to replace current telephone lines.

J

Jitter
An issue occassionally associated with videoconferencing over packet networks. Is caused when there is a variation in network latency, meaning that the image appears stuttered and doesn't flow. Occurs when there is no guaranteed Quality of Service (QoS) during a videoconferencing call and results in loss of image and audio quality.

K

L

Lag
Sometimes refered to as High latency. Associated with network problems and results in a loss of the syncronisation between audio and image.

Latency
The speed at which videoconferencing (audio and video) data takes to make the journey from sender to recipient.

M

Multipoint Conference Unit
The Multipoint Conference Unit (MCU) is an important part of any videoconferencing infrastructure, allowing three or more parties or persons to get together in a virtual meeting room.

Multipoint Connections
Direct Visual’s industry leading IP/ISDN multipoint conferencing service. A booking service designed to take away the stress of managing your own multipoint calls.

Multipoint videoconference
Videoconference with more than two sites. The sites must connect via a video bridge. (Compare with point-to-point videoconference.)

N

NAT
Network Address Translation (NAT) is the translation of an Internet Protocol address (IP address) used within one network to a different IP address known within another network. One network is designated the inside network and the other is the outside. Typically, a company maps its local inside network addresses to one or more global outside IP addresses and unmaps the global IP addresses on incoming packets back into local IP addresses. This helps ensure security since each outgoing or incoming request must go through a translation process that also offers the opportunity to qualify or authenticate the request or match it to a previous request. NAT also conserves on the number of global IP addresses that a company needs and it lets the company use a single IP address in its communication with the world.

Narrowband
A low-capacity communications circuit/path. It usually implies a speed of 56Kbps or less. (Contrast with wideband and broadband)

O

P

Point-to-point videoconference
Videoconference between two sites. (Compare with multipoint videoconference.)

Polycom
American based videoconferencing manufacturer: have been number one in the world for a number of years in their industry. Direct Visual is a Polycom Authorised Reseller and a Polycom Authorised Service Partner.

Proprietary compression algorithm
A vendor-specific algorithm for compression of a video signal. A videoconferencing system using a proprietary algorithm can only communicate with a remote site using the same algorithm. Many vendors also adhere to standard compression algorithms to facilitate communication across platforms.

Q

QoS (Quality of Service)
A term commonly used when refering to a network, its quality and its reliability. Quality of Service on a network will guarantee a good standard of call and a definite amount of bandwidth.

R

Radvision
Israel based network infrastructure manufacturer. Direct Visual is an authorised reseller of Radvision products.

S

Stratus
Direct Visual's IP based Videoconferencing managed service network.

Switch
A switch is a network device that selects a path or circuit for sending a unit of data to its next destination.

Subnet Mask
The subnet mask is used to determine where the network number in an IP address ends and the node number in an IP address begins. A node is anything on a network that needs an IP address to communicate (a PC, server, router, etc).

Standard compression algorithm
An algorithm convention for compression of a video signal. Adherence to standards allows communication among a wide variety of videoconferencing systems, though not with the same clarity as two similar systems using a proprietary algorithm. H320 is the most widely accepted standard in use today.

T

TANDBERG
Norwegian based Videoconferencing manufacturer; one of the world’s leaders in the industry. Direct Visual is a TANDBERG Accredited Service Partner and a TANDBERG Platinum Partner.

Terminal Equipments
Room System
A room system is a vendor’s top of the line product designed to provide medium and large corporations, government, and educational institutions with custom room configurations. These systems are used in situations requiring high-quality video performance and extensive conferencing capabilities for applications such as distance learning, boardroom conferencing, and high performance multi-site conferencing. Performance is based on providing IP data rates as fast as 2 Megabits per second. These systems typically support multiple video and audio inputs such as document cameras, computer video converters, and VCRs. Support for one to three video displays is also common. Complete systems may come with two or more 32” viewing monitors or can be used with larger projection systems. These systems can be permanently built into a room or set up as semi-mobile units that can be taken to another room if necessary. Some units even have built-in streaming services. The main advantages to these systems are video quality and built-in multipoint services.

Set-Top System
The term set-top system usually refers to a vendor’s mid-level product designed for small to medium sized conference rooms. This system can look just like the room system with monitors and carts, or it can be a smaller unit that sits on top of a monitor. These systems typically will perform the same as the room systems at lower data rates; however, the set-top systems typically do not support data rates above 768K and do not have the built-in multipoint conference capability. One advantage to the set-top solution is that products on the lower end of this pricing scale can give a user excellent conference room or classroom performance as long as they do not require the extra services or options offered by the room systems.

Desktop System
A desktop system, simply put, is a video conferencing terminal, either hardware or software, that interacts directly with the personal computer on a desk. It is designed to be a one-person unit, making it unsuitable for a conference room environment; but it can be very useful for an office or classroom/lab-station solution. It will either connect through the USB port or will have a hardware card to be installed. The speed of the computer processor will directly affect performance. The advantage of such a unit is its low-cost focus on an individual user, with no special room or setup needed. Within minutes of installation, a user can talk face to face to someone using another desktop system or someone with a room system. The disadvantage to this type of system is that it is not designed for conference rooms. .

U

V

Videoconferencing / Video Conferencing / Videoconference / Video Conference
Communication across long distances with video and audio contact that may also include graphics and data exchange. As supplied by the UK's leading videoconferencing products and services provider, Direct Visual.

Video bridge
Computerized switching system which allows multipoint videoconferencing.

W

Wide Area Network (WAN)
A communications network that services a geographic area larger than that served by a local area network or metropolitan area network.

X

Y

Z

Zone Prefix
A prefix that identifies the addresses to be serviced by a given gatekeeper. Zone prefixes are typically area codes and serve the same purpose as the domain names in the H.323-ID address space.