Glossary

Glossary Listing: A

• ADC: Analog-to-Digital Conversion Process of converting analog signals to a digital representation. DAC represents the reverse translation.

• AGC: Automatic Gain Control. Ensures the same audio level for all participants in a video conference.

• analog signals: 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.

• ANS: Automatic Noise Suppression.

• application sharing: A feature of many videoconferencing and Web conferencing applications that enables the conference participants to simultaneously run the same application. The application itself resides on only one of the machines connected to the conference.

• application viewing: In Web conferencing, the users sharing the application can see every keystroke or mouse movement made by the one user who is running the application. The other users have no control over the application.

• archived Webcast: An encoded media file that is stored and downloaded for playback by an end user in a future period of time.

• artifact: Visible degradations of an image resulting from any of a variety of processes. In digital video, artifacts usually result from color compression, and are most noticeable around sharply contrasting color boundaries such as black next to white.

• ASF: Defined by Microsoft, "ASF"” stands for Advanced Streaming Format. ASF is the file format in the Windows Media architecture.

• asynchronous: Not coordinated in time; contrasted with synchronous. In a typical synchronous protocol, each successive transmission of data requires a response to the previous transmission before a new one can be initiated. An asynchronous protocol allows transmissions to occur independently of one another. In computer communications using asynchronous protocols, each piece of data usually has a start bit at the beginning and a stop bit at the end, so that the valid data can be distinguished from random noise. Most communications between computers and devices are asynchronous; the public Internet is based on an asynchronous system.

• 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"”).

• attachment: Files or Web pages enclosed within an e-mail message.

• audio: In communications, electrical signals that carry sounds. The term is also used to describe systems concerned with sound with recording and transmission; speech pickup systems, transmission links that carry sounds, amplifiers and the like. Example devices: microphones, audio mixer.

• audio conference bridge: A device that is designed to link three or more telephone channels for a teleconference. Usually refers to a bridge that provides only dial-up teleconferencing where an operator calls each participant. Contrast to virtual meeting room bridge.

• audio conference dial-in number: The telephone number dialed by parties in order to audio conference. For participant convenience, the same local or toll-free telephone number is often used for an individual account.

• audio conference ID: A 7 to 10 digit number used to identify the particular audio conference meeting the caller wishes to attend.

• audio conference participant: An invited party to a telephone conference. Participants join a conference by dialing the conference dial-in number and inputting the correct conference ID number.

• audio conferencing (also called audio teleconferencing): Two-way remote voice communication among multiple individuals using a telephone, audio connection device, or VoIP.

• audio site: A site that participates in a meeting using a standard or mobile telephone.

• audio-only conference add-ins: The ability to add another site into a video conference via an audio connection only. This feature uses a regular phone line connected to the codec to conference in someone who is not near a video site but needs to be part of the conversation.

• audiographics: Audiographics combines audio, network abilities and graphics into an integrated stream that is transmitted via what is known as a 'narrow band' conduit. An examble of this 'narrow band' technology would be a telephone line. The net result of using audiographics is to create a more interactive experience for the end users at remote videconference sites.

• authoring software: A software package that allows a user to create interactive media and multimedia presentations incorporating text, sound and pictures.