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2. USER REQUIREMENTS FOR MULTIMEDIA
2.1. Human - Computer Interface
The standards of reproduction for computers which are desirable have been set by the publishers of books, music, Walt Disney cartoons and television producers. With the development of High Definition TV and beyond, it is likely that there will be a continual increase in the demands placed on computer based multimedia systems.
The current PAL standard in the UK delivers video in 625 lines at 25 frames/sec. High Definition TV delivers video in 1250 lines with a higher horizontal resolution at 25 frames/sec and requires about five times the information rate as the current PAL system.
Multimedia applications like any other application, appliance or tool, benefit from being easy to use, with minimal training or self learning. The need for a well designed human - computer interface, which may be screen or audio based is well accepted.
2.2. Access, Delivery, Scheduling and Recording
Television channels can be changed at the touch of a button. On demand access times to computer information need to be below one second to be usable in real time. Alternatively the delivery of information at a later time is acceptable if it can be scheduled, as in a TV broadcast schedule, or a first class postal letter. Scheduling the delivery of multimedia information has not been widely implemented. Scheduling can have advantages for users over on demand delivery. In a learning situation times can be defined for class attendance by a lecturer. In open learning situations learners can control their programme by requesting a multimedia unit at a
Just as we can record a TV film on a VHS recorder, some multimedia computer users will wish to record a film, session, or learning experience for future reference.
Interactivity, meaning the ability to participate in a video or audio process on a computer, by changing its behaviour or appending comments has become very important in multimedia. Some of this popularity stems from the perception of computer games as being enjoyable because they are nteractive, and some from work done in education which shows that some types of learning becomes easier, and is retained more permanently if the learner participates in some way with the learning material. Computer based multimedia needs the same degree of interactivity that a school exercise book, or a laboratory experiment has in order to remain credible as a learning medium. The generation of computer based virtual reality is an extension of this process. The incorporation of interactivity is really the job of the application designer. The incorporation of interactivity is assisted if the network is capable of two way communication, and for some applications the sense of interactivity is aided by the ability to deliver a moving picture, or a sound very quickly, so that a sense of two way human participation can be generated. Real time video conferencing is an example.
2.4. Educational requirements
An Open Learner needs to be able to use any multimedia application at any time. However since open learning is often undertaken in centres, the use of audio and video require particular thought. Obviously several sets Sound Blaster driven speakers will disturb those learners working on a computer based self test! Similar considerations occur for users of multimedia in a class situation, such as a language teaching application. Not only will a number of students be performing similar activities at the same time on a network but the lecturer must decide whether to control the activities via the media of the computer. The use of multi-party desktop conferencing with the lecturer chairing the running of the conferencing session, showing
selected parts of a video etc. is a case in point.
Distance learners or users of multimedia will also be capable of having same impact on a network as several students playing the computer game Doom at lunchtime. Additionally the co-ordination of a learning activity must also be done by a lecturer over the network. So the role of the chair in multi-party video conferencing is crucial.
In education the main costs visible to multimedia users to date have been the cost of the computer platform, the CD-ROM, and the software. Network costs are usually borne centrally within an institution, or by JANET nationally. The increased cost of providing sufficient network capacity and ability of new networks to charge on the basis of bandwidth used mean that individual users will increasing have to consider the costs of access when designing or using multimedia applications. Additionally information providers, electronic publishers, etc. will begin to incorporate charging mechanisms in their systems [Nelson94].
The educational user ideally needs the costs of use to be well defined, in advance so applications teaching journalism, which make repeated access to Reuters databases would not be viewed favourably by educational managers.
Cost benefit analysis of multimedia distance learning, and open learning proposals will increasingly become the norm.
Virtual Environments Visualisation