Decoding
Once the multimedia data has been received by the end-user it needs
to be decoded and displayed. The appropriate software to decode the data and display
or play it in its original (or as close as possible to original) form needs to
exist on the user’s computer. For instance, the Adobe Acrobat viewer to display
PDF files, a RealAudio player to play audio files, or a QuickTime player to play
quicktime files.
For pure audio or video material, the player software may have a
user interface resembling a tape player, complete with the controls for play, pause,
fast forward and fast rewind. For these controls to work, the player and the media
server must be able to communicate. Other applications may require different kinds
of interactivity, such as editing functions for a system developed to support media
production, or user-control of an object on a screen, or the event sequence for
a system to support distance education. At present this communication is achieved
through the use of proprietary protocols, although the MPEG-4 standard for interactive
media is currently being developed, which will define a standard for the control
of multimedia objects.