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Human history has developed through the storage and distribution of information. Initially this involved writing and distributing material in a printed form such as with books, news-papers, leaflets and posters. One of the first changes to this type of distribution came when Ted Nelson, in 1960, published 'As We May Think', which was basically a description of a global document system, based on the hypertext principle. This paper inspired many people including Tim Bernes-Lee at CERN who, in the 1980s, actually developed the first prototype of the WWW. A major change has thus occurred over the last century where com-puters were used to distribute, store and present information.

Up until the end of the 1970s, computers systems could only really support text-based information, and were large, and difficult-to-use systems. The great change in computer systems came in 1981, when IBM released the PC. This was followed, in 1984, by the Apple Macintosh and in 1985 by the Commodore Amiga. The Macintosh and Amiga were based around GUI's and their applications used WIMPs (Windows, Icons, Menus and Pointers). These concepts allowed for proper multimedia. The PC would eventually catch up with the usage of Microsoft Windows, which was a GUI for the PC. Slowly the PC has supported mul-timedia, with the additional of graphical cards, audio cards and high-speed CD-ROM drives.

Before the integration of multimedia on computers, the media tended to be delivered in a non-computer-based way, such as through video, or audiotape delivery, or even over TV systems (such as used by the Open University). These systems did not provide much interaction between the trainer and the user. The new integrated multimedia systems supported the integration of audio, video, graphics and text. Initially the production of this material was difficult as there were very few development packages available, but over the 1990s, several companies, especially Macromedia and Adobe, produced development packages, which successfully integrated all the media into a single form.

Multimedia is the integration of many different media types into a single integrated unit. This normally involves converting the original media source, such as images, audio, video, text, and so on, into a digital form, so that it can be integrated into a digital package. This can then be delivered as a single entity. Figure 1 illustrates this.

Figure 1 Difference between server-side include and client-side include (©billatnapier)

For example video is normally available in either an NSTC, PAL or SECAM format. This can then be digitized into a digital form. This will give RGB and pixel data, arranged in frames. Next the video can be compressed into a standard format, such as MPEG or AVI. Sound can be converted into MP-3, and images are typically converted into JPEG, GIF or PNG. The output from the media integration package depends on how the media will be delivered. The main forms are:

Stand-alone package. This is where the media has to be run without requiring any additional software viewer. Typically, it is compiled for the specific computer and operating system that it will run on.
Media player integration. This involves converting the media into a form which can be played in a media player. Typical media players include Macromedia Shockwave Player (which plays DCR files), Macromedia Flash Player (which plays SWF files). The forms can also be integrated into a WWW browser (using the required browser plug-in).
WWW integration. This involves converting the media into a form which can be viewed by a WWW browser. For this the media is converted into a number of HTML pages, which contain media content, such as AVI, MPEG, GIF, JPG and PNG files. Note that ad-ditional plug-ins are required for the delivery of AVI and MPEG movies. A typical player is Quicktime, which is available from Apple Computers.
Real-time delivery. This involves delivering the media, in real-time over a network con-nection. Sometimes this can involve the synchronization of images or video with sound. Typical real-time formats include the Real Audio (RA) format, and Windows Media Audio (WMA).

Raw sources of contentCoversions from analogue to digitalUses compression techniques such as LZ, Huffman, and so on.The integration package