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11. NETWORKED MULTIMEDIA APPLICATION DESIGN

11.1. Real Time Multimedia Applications

A number of real time applications are available for use over networks based on computers, which are capable using audio or video. The two networks over which applications have been developed td date include ISDN, Local Area Networks, and Local Area Networks connected over high speed ATM or SMDS connections. The table below summarises the most important applications with examples.

Application                  ISDN                         LAN's 
Desk Top Conferencing	Proprietary Desktop          wb...  an Internet white board
                        conferencing systems 	     tool, proprietary software. 
Video Conferencing	H.320 video conferencing     vat ... AVisual audio internet
                                                     tool, ivs... video conferencing software
Video Mail              Based on H.320 video         X.400 and MIME electronic
                        conferencing	             mail with video content.
Remote Image viewing    Medical applications,        Medical Applications.
 and manipulation          eg X-Rays                 Multicast of JPEG Satellite
                                                     images
Information Kiosks	Proprietary systems	
Distance Learning       File Server Access           File Server Access

11.1.1. Desk Top Conferencing

Desk Top Conferencing is a means of working with a remote user on their computer running the same application. Typically a drawing or spreadsheet will be transmitted via the ISDN line. A voice conversation between the two users can be held at the same time. Within desk top conferencing remote control of a computer is possible. Since these applications must reproduce the screen of a PC on another, the speed of the connection between the two computers is important. Products are available from Fujitsu for LAN and ISDN use and IBM (Person to Person). Desktop conferencing is also available over some of the video conferencing products such as the Olivetti PCC.

The standardisation of multimedia conferencing using the T.120 series of International Telecommunication Union standards is now widely accepted. Products based on these standards are likely to appear on the market next year from several manufacturers. The applicability of the T.120 standards will not be limited to WAN or ISDN networks, but will be appropriate to Local Area Networks too.

The T.120 standards will apply to terminal with audio, audio and interactive video, or interactive graphics or all three. It will support point to point and multi-point conferencing. ISDN is the initial focus. Work is underway to define ATM support. Areas to be standardised include still image, annotation, application sharing, conference control, and multi-point conferencing. The standard set will be largely defined in early 1995.

11.1.2. Video Conferencing or Videophone products

Until recently the only implementations of video over the telephone network have been poor quality video phones or very expensive video conferencing for executives.

A selection of video conferencing products is listed below:

VidiMac for the Apple Mac based on the Planet ISDN card, which uses motion JPEG techniques.

IBM, Fujitsu, and Olivetti have video conferencing products based on the BT VC8000 PC card. The IBM product is called Screen Call, the Fujitsu is called Team Vision, and the Olivetti is called PCC. All three use the services of the VC8000 card in different ways. The common feature is support for H.320 video conferencing. Support is available in all three for file transfer, whiteboards, and remote control. All retail for around the Ł3000 mark.

Intel have released a product called ProShare, which is very competitive, but at present will not work to the H.320 standard.

Northern Telecom have a product called Visit 2.0 which runs on a PC or Mac. It uses external ISDN Terminal adapters and audio transmission need to be via an independently set up telephone call.

Invision have made proprietary non H.320 video conferencing available for LAN connections running LAN protocols such as TCP/IP. Frame rates range from 1 to 20 frames per second with corresponding data rates fro 64 to 512 kbps.

Picturetel Live PCS100 is one of the more expensive PC based products, but manages excellent quality through good implementations and extensions to the H.320 standard. Full CIF pictures are available. At QCIF resolution of 7.5 frames per second are available.

The Olivetti PCC based on the BT VC8000 PC card provides QCIF at 15 frames per second, audio, file transfer, whiteboard, remote application control, remote form entry, image capture and transfer, and a text chat mode. All of these applications are programmable and should users should use this feature to customise the screen interface, which is based on standard Windows 3.1 menu bars and buttons. Interfaces are available for video and audio from other sources. All of these facilities are programmable and customisable. H.320 standards are supported. T.120 conferencing will be available in 1995. Price is about Ł3,500.

Most of these products will provide ISDN applications such as file transfer, but the additional facility of a quarter screen video picture of the caller will be available in colour. Compression techniques are used to improve the quality of moving pictures. Sadly these some products use different compression methods so they cannot communicate with each other. But with manufacturers moving to the H.320 series of compression standards, at least for video phone communications this situation may improve. Other standards e.g. MPEG are be better for straight video broadcast.

11.1.3. Video Mail

Video mail can be delivered via X.400 mail, or Internet mail with MIME extensions for file attachments. Obviously transmission times can be longer. An appropriate viewer (hardware or software) is then needed to replay the mail.

An alternative approach has been taken by Olivetti, who will release in 1995 extensions to the PCC video conferencing system. These extensions will enable video and voice messages to be left on a PC for viewing by a local or remote user connected over ISDN.

11.1.4. Image Viewing

An image database is considered to be a useful application for attachment to existing databases, or for standalone use. Products have been design for both general use and access via ISDN. Most products are designed not as stand alone image viewers but as part of an information system or kiosk for tourism or specialist applications. An example of the latter is a system from On Demand Information which markets a database for the building industry, accessible over ISDN.

11.1.5. Information Kiosks

Information kiosks are starting to appear with multimedia features. Information kiosks have commercial applications in tourism, government information and education. Extensive multimedia material can be held on local hard discs and updated at regular intervals, manually or via a network connection such as ISDN. The Olivetti PCC video conferencing system allows video conferencing to be incorporated in the design of an information kiosk. All the functions of the system can be programmed from within a high level language such as C++ , Toolbook or Visual Basic.

11.1.6. Distance Learning

Distance learning applications can held on a network file server. They can then be accessed from the local LAN or by ISDN. The high speed of ISDN means that the remote connection of PC's to LANs is now viable. The response of a distance learning application running over ISDN instead of a local LAN will depend on its design and the amount of visual material. transfer of audio material will also take time and require a remote workstation set up for audio playback.

A remote access connection over ISDN to a LAN can be set up in three ways:

(a) Setting up a serial synchronous or asynchronous connection using terminal adapters to link the PC into a conventional LAN bridge or router.

(b) Placing an ISDN card in the remote PC and a similar card in a dedicated PC which is also connected to the LAN via an Ethernet card. The latter then acts as a dedicated gateway and is sometimes sold as a dedicated box.

All of these methods require appropriate software to be run on the PC and gateway/server. LAN access is available for the Novell IPX and TCP/IP protocols, for Ethernet and Token Ring LANs.

The costs of such access range from Ł1000 to Ł5000 at the central site, and from Ł300 to Ł600 at a remote location, excluding the costs of ISDN provision and calls. Reliable systems, reasonably easy to set up, are available. Further information is available below in section 11.2.2.

Distance learning can take many forms as pioneered by the Open University in the UK. The development in the communications technology and computer systems has resulted in an increase interest towards the support of this mode of study using multimedia. One such project [An93] was conducted at the California State University at Chico. The trials aimed to assess the viability of using Integrated Services Digital Networks (ISDN) Basic Rate Interface (BRI) (128Kbits/s) for transmission of voice, data, and video. The distance learning trial was divided into several phases. Phase I involved a point-to-point trial between two locations. Phase II demonstrated the interlocated access transport connectivity. While phase III involved the use of networked-based bridging equipment to accommodate simultaneous instruction to three separate classes. A list of the components and hardware and software configuration can be found in reference [An93].

The evaluation of the experiment has found the following:

Audio quality is very important. Even though the video, still image, and graphics media are available, the overall perception of the service is greatly affected by the quality of the voice communications.
For distance learning applications, the ISDN bandwidth of 112/128 kb/s delivers adequate real-time video quality.
Animated graphics, audio, and two-way video are effective ways to instruct students in remote classes [An93].

Contents

Graphics Multimedia Virtual Environments Visualisation Contents