Glossary of Videoconferencing Terms

C,D

Cable Modem
A hook up to your cable TV system that allows you to transmit computer information and access the internet through your cable company.

Camera Presets
Allows predefined camera angles to be programmed into a videoconferencing system.

Codec
Coder-Decoder. A codec is the core (or "engine") of a videoconference system and is responsible for all of the encoding and decoding of information (audio, video). Before the transmission, the codec converts analog signals to digital signals and compresses the digital signals. Incoming audio and video must be decompressed and converted from digital back to analog.

Compressed Video
The codec compresses the information into smaller pieces for easier and faster transmission. This allows the information to be transmitted faster over smaller capacity lines. Due to the compression and decompression of information some of the original quality of the video and sound are lost which results in diminished picture and sound quality.

Desktop Videoconferencing
Videoconferencing on a personal computer. This is the most economical type of Videoconferencing systems. It is most useful for individuals and smaller groups.

Document Camera
A camera used during a videoconference for taking pictures of still images, pictures, graphics, pages of text, and 3-D objects. All images can be sent stand alone to a TV monitor or as part of a videoconference.

Document Sharing
Allows users on both sides of the videoconference to view and edit the same computer document.

Digital Signals
A digital signal can only have a certain number of defined values (like, 0 or 1). This is different from an Analog signal that could have any value within a given range. In general, because of having only a certain number of defined possible values, a digital signal provides better performance than an analog.

E, F, G

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

Ethernet
A Local Area Network (LAN) running on coaxial or twisted pair wiring at 10 or 100 Mbps. (Large Bit Ethernet is slowly becoming available.)

Frame Rate
Frequency that the video frames are displayed on a monitor, typically described in frames-per-second (fps). The higher the frame rate the better the quality of the video.

Full Duplex
Sending audio data in both directions at the same time. Usually higher quality, but requires more bandwidth. Provides much more natural and useable audio to a videoconference because people on either end of the conference can speak at the same time.

Gateway
The interface between two opposing protocols, typically h.320 and h.323. By means of software and hardware, a gateway allows connection between otherwise incompatible networks.

H, I, J, K

H.239
ITU Standard for sending data long as a dual stream in a videoconference.

H.264
ITU Standard for video compression sometimes referred to as MPEG 4 part 10.

H.320 Standard
A commonly used video compression standard for videoconferencing over networks that provide fixed communication paths (such as the ISDN phone network). By defining standardized ways of performing all of the processing that has to be done by a videoconference system, systems from different vendors can communicate with each other as long as they all comply with the standards. H.320 references many other standards for specific tasks (such as audio coding or video coding).

H.323
This is also a top-level standard, like H.320, for videoconference systems. The difference is that H.323 defines methods to be used on what are called packet-based networks (which are also called IP (Internet Protocol) networks) like a typical business, school LAN or the Internet.

H.324
The standards used to specify voice and video transmission over traditional analog phone lines.

Half Duplex
A telecommunication system where data can only flow in one direction at a time. For example, a half duplex speakerphone only allows one person to speak at a time.

High Definition 720p - 720p
720p - 720p is the designated name for one of the HDTV video modes. 720 represents 720 lines of vertical resolution, and the letter p stands for progressive scan (non-interlaced). The horizontal resolution of 1280 dots across and a frame resolution of 1280 x 720 with an aspect ratio of 16:9.

High Definition 1080i - 1080i
1080i - 1080i is the designated name for one of the HDTV video modes. 1080 stands for 1080 lines of vertical resolution, while the letter "I" stands for interlaced or non-progressive scan. The horizontal resolution of 1920 dots across and a frame resolution of 1920 × 1080 or over two million pixels with an aspect ratio of 16:9. In addition a field resolution of 1920 × 1080/2 (interlaced) or about 1.04 million pixels.

High Definition 1080p - 1080p
1080p - 1080p is the designated name for one of the HDTV video modes. 1080 represents 1,080 lines of vertical resolution, and the letter p stands for progressive scan (non-interlaced). The horizontal resolution of 1920 dots across and a frame resolution of 1920 × 1080 or over two million pixels with an aspect ratio of 16:9.

IP
The Internet Protocol. IP is the basic language of the Internet.

IP Multicast
A technique for "many to many" communications over an IP network. Multicast is scalable and gets to a larger viewer population by not requiring prior knowledge of who or how many viewers there are. Multicast utilizes network infrastructure efficiently by requiring the source to send the information only once, even if it needs to be delivered to a large number of viewers. The network nodes will replicate packets as needed to reach multiple viewers as necessary.

IP Unicast
A technique where a IP network distributes packets of information to a single destination. Each viewer would have their own separate stream of the same information sent through the network.

ISDN
Stands for "Integrated Services Digital Network". A type of telephone network that uses digital service right up to the end user's equipment (like an ISDN modem). This type of telephone network also uses separate paths or channels for signaling so that the signaling information does not interfere with the data being sent by the user. It provides seamless communications of voice, video, and text between individual desktop videoconferencing systems and group videoconferencing systems. It allows for faster data transfer rates than existing analog lines.

kbps
It stands for "kilobits per second". The "kilo" means "thousand". This term is used when talking about the speed that a device (or circuit) can transport data. For example, a 56kbps modem could transmit 56,000 bits in one second.

L, M, N

LAN (Local Area Network)
A computer network linking workstations, file servers, printers and other devices within a local area, such as an office. LANs allow the sharing of resources and the exchange of both video and data.

Modem (MODulator-DEModulator)
Allows the transmission of digital information over an analog phone line.

Multipoint Videoconference (via MCU)
Videoconference with more than two sites. The sites must connect via a video bridge, which is also called a Multipoint Control Unit (MCU).

O, P, Q

Packet Based Network
A network where data is sent in small chunks, called packets. There is not a fixed path from the sender to the receiver, so each packet (chunk of data) has to identify the source and destination. Most corporate LANs (and the Internet) are packet based.

Point-to-point Videoconference
Videoconference between two sites.

POTS (Plain Old Telephone System)
This is the traditional analog system for voice we use at home.

PRI (Primary Rate Interface)
Another type of ISDN phone line with much higher capacity (23 B-Channels that can carry up to a total of 1472kbps). This type of circuit might be used by schools or businesses and may be shared between several users or devices.

PTZ (Pan, Tilt, and Zoom)
Remote control features that typically come with high-quality cameras that are used in room-sized videoconferencing systems.

R, S, T

Real Time
A transmission that occurs right away, without any perceptible delay.

Room-based Videoconferencing
Videoconferencing using a larger and more sophisticated system. These systems can be mobile stand-alone systems or customized for the needs of the user. These systems are more appropriate for large groups and more sophisticated techniques.

Standard Compression Algorithm
This is a standard algorithm convention for compressing the video signal. This allows different videoconferencing systems to communicate with each other successfully. This does not always provide the same clarity as two similar systems using a proprietary algorithm. H.320 is the most commonly used standard.

Streaming Media
Sending video or audio over a network as needed, instead of forcing the user to download the entire file before using it. Typically a few seconds of data is sent ahead and buffered in case of network transmission delays. (Although some data is buffered to the hard drive, it is written to a temporary storage and is gone once viewing is complete.)

T.120
Another standard. This one defines the way in which data and computer applications can be shared between two or more users.

T-1
Network link used on the Internet allowing speeds of up to 1.54 megabits/second.

T-3
Higher speed (45 megabits/second) network link used on the Internet.

TCP (Transmission Control Protocol)
works in conjunction with IP to ensure that packets reach their intended destinations.

TCP/IP (Transmission Control Protocol/Internet Protocol)
The suite of networking protocols that let different types of equipment communicate over the Internet or other packet based networks.

U, V, W, X, Y, Z

Video Bridge
Computerized switching system (also known as MCU - Multipoint Control Unit), which allows more than two sites to communicate using videoconferencing. Many companies now offer bridging services for a set fee.

Videoconferencing
Interactive communication using video and audio to communicate over long distances. It combines the interactivity of the telephone with the visual stimulation of the television. Videoconferencing may also include graphics and data exchange.

WAN (Wide Area Network)
A communications network that services a geographic area larger than that served by a local area network or metropolitan area network. WANs include commercial or educational dial-up networks such as CompuServe, Janet, and BITNET.