This report is also available as an Acrobat file.
Factors affecting videoconferencing uptake
A few years ago there was concern over a number of hurdles which needed to be overcome in order for the full potential of videoconferencing to be realised. Many of these have now been resolved including:
- The establishment of the H.320 standard for video codecs.
- The development of ISDN dial up service and consequent reduction in transmission costs.
- The improvement in compression techniques and subsequent improvements in audio and video quality.
- The establishment of ETSI standards, and creation of an integrated market in Europe.
- The evolution of video onto the desk-top with the introduction of multimedia terminals and enhanced user interfaces.
The key to the further development of videoconferencing lies with the convergence of ISDN and LAN with the existing PC based multimedia and video compression technology. Essentially this will give digital communications the effectiveness of personal meetings, the convenience of a telephone, and the power and facilities of a personal computer.
In the UK the growth of videoconferencing, particularly in the higher education domain, will rest upon the development of SuperJANET, the drive to provide useful bandwidth throughout the education network.
SuperJANET (Joint Academic Network) is the government funded project to link 100 British Universities. Videoconferencing equipment supplied by GPT Video Systems is planned to link up the first 50 universities by the end of this year. The network provides 140 Mb/s links, compared to the 2Mb/s links of Janet
Factors for consideration in the implementation of videoconferencing, are the networks and the standards.
For the networks the first step is ISDN, this was defined by the CCITT as:
“A network, in general evolving from a telephony IDN, that provides end to end digital connectivity to support a wide range of services, to which users have access by a limited set of standard multipurpose user-network interfaces.”
ISDN stands for “Integrated Services Digital Networks”. It is basically the existing telephone network using existing but upgraded switches and wiring, but all digital, giving a bandwidth for a basic call of 64kbps. This increased bandwidth allows the transmission of high fidelity compressed audio, as well as the potential for video communication. It also, incidentally provides enhanced services.
Broadband ISDN (B-ISDN) refers to services that require channel rates greater than a single primary rate channel. B-ISDN services are usually categorised as
- Conversational — videotelephony, videoconferencing
- Messaging— electronic mail for video, images
- Retrieval — teleshopping, news retrieval
- With user control— teleadvertising, remote education
- Without user control — electronic newspaper, TV distribution.
Videoconferencing over ISDN is governed by a set of CCITT standards which en sure interoperability. The main standard is the H.320, which encompasses most of the others. This specifies H.261 for video compression, H.221, H.230 and H.242 for communications, control and indication, the three G. standards for audio (711, 722 and 728) with a number of other ancillary standards. For full interoperability all of these standards should be complied with, and not simply the H.261 video compression standard as many equipment manufacturers would like one to believe.
In the UK ISDN lines can be installed and rented through both BT and Mercury.
The Super Joint Academic Network, is an advanced high speed optical fibre network, being implemented by the academic community and BT. It currently provides three services; a high performance Internet service to all sites, and ATM (Asynchronous Transfer Mode) to some of the sites, and a video network to some of the sites. Access to the Internet and ATM services is at 34 Mbps, but this is due to be upgraded. By 1997 there is talk of 600Mbps. Advice for connection to SuperJANET can be obtained from UKERNA (UK Education and Research Networking Association), the address of whom is appended to this document. At last count 57 universities were connected to the network, but only 14 of these have access to all three services.. These figures are expected to grow continually.
There are a number of internationally agreed standards covering all aspects of the technical processes involved in encoding and compressing video signals, mixing audio and video data, multiplexing this with other data, and transporting the signal through the network. These ensure compatibility between terminals from different manufacturers, they do not seek to ensure a degree of quality, but simply connectivity. A list of relevant standards with their definitions are incorporated into Appendix 1.
The EVE Program
Six leading European Telecommunications companies have formally agreed to co-operate in establishing a pan European videophone service. The initial members of the consortium were BT, Deutsche Bundepost Telekom, France Telecom, Norwegian Telecom, PTT Telecom Netherlands, and SIP Italy. The primary aims of this group is to raise the awareness of videotelephony, create a better understanding of the benefits to users, and to ensure that future developments of the technology comply to the existing standards.
Virtual Environments Visualisation