Multimedia Conferencing on LAN

Abstract

There has been a steady increase over the past few years in the use of networked multimedia. Advances in standard PC technology together with the growth of Internet and networking, has resulted in a popular rise in applications such as audio/video conferencing and collaborative working environments. Many new multimedia computers arrive with both sound cards and real time video grabbing capability installed as standard. Real-time data presents a problem for data communications in that it requires an almost constant level of sampling whilst maintaining a steady transmission rate with the minimum of delays. Various data networks including the Internet can be used to transmit audio and video. Data packets of 20, 40 or 80msec duration can be transmitted to either one or many network users via the same networking protocols that are used for web and email. Like these other network applications, multimedia data can also be affected by network congestion. In busy networks, data packets can become "lost". Applications that are not reliant on real time transmission do not suffer irreparable damage in this instance; the client (receiving) computer notifies the remote server that certain packets did not arrive and the server simply resends the data until the client acknowledges a full successful receipt. Even in the busiest of networks, the end user will eventually get the full email message or web page from the remote machine even if there is a substantial delay. For real time, interactive data transmission, any delay can potentially cause major problems for the quality and usability of the system in question There has been a considerable amount of research into the area of video and audio quality. Video quality is measured in terms of the user’s perception of variations in frame rate, image size, packet loss and audio/video synchronisation; while audio quality is measured in terms of loudness, tone and intelligibility (Watson & Sasse, 1997). Due to the limitations of bandwidth and consequently expense, specific research into the necessary levels of audio and video quality has also been conducted. Many multimedia developers and network service providers are aware that a compromise can be reached between cost and certain levels of quality to maximise user performance and satisfaction and cost.