AGOCG logo
Graphics Multimedia VR Visualization Contents
Training Reports Workshops Briefings Index

Multimedia Standards

 Back Next

Introduction
  
Multimedia
  Hytime
  MHEG
  PREMO
  MIME
  QuickTime
  
Markup and PDL
Graphics
Audio
Video
Video Conferencing
Virtual Reality

Multimedia Standards

HyTime

ISO/IEC 10744:1997
This is an SGML based hyperdocument structuring language for representing hypertext linking, time scheduling and synchronisation. It does not provide a way of coding multimedia presentations, but a language to describe how hypermedia objects are interconnected, and how users can access them. Application specifications will be created and exchanged in the form of an SGML DTD (document type definition) HyTime has five modules, of which only the first is compulsory:
  • the base module provides facilities required by other modules
  • the location address module provides facilities for locating objects in the data
  • the hyperlinks module allows linking elements to be identified and managed
  • the scheduling module allows data elements, locations or links to be scheduled as events within a presentation
  • the rendition module allows data to be modified to a suitable form prior to presentation
For more information see the OII Standards Page

MHEG

(ISO/IEC JTC1/SC29 WG12)
MHEG is a specification for the representation of final form (ie non editable) multimedia and hypermedia objects. These objects define the structure of the presentation in a platform independent way, and provide functionality for real-time presentation, synchronisation and interactivity. Because it is a self-contained architecture it can run in limited resources (memory, computing capability), for example in set-top boxes for games machines or home-shopping. The standard was developed with the following objectives:
  • Interchange - of different media types
  • Presentation - the media type is identified and appropriate resources used for presentation. Different media types can be grouped into a single presentation
  • Use minimal resources
  • Real time interchange and presentation
MHEG is divided into the following parts:
  • Part 1: MHEG Object Representation, Base Notation (ASN.1). This defines the objects and their behaviour
  • Part 3: MHEG Script Interchange Representation, an executable code dedicated to a virtual machine, the SIR (Script Interchange Representation)
  • Part 4: MHEG Registration Procedures
  • Part 5: Support for Base-Level Interactive Applications, to allow the development of an interpreter requiring few resources
  • Part 6: Support for Enhanced Interactive Applications, an extension to MHEG-5, adding computing and communication functions with the external environment.
  • Part 7: Interoperability and Conformance Testing (under development).
For more information see:

MHEG 5 User Group - news, links and an MHEG FAQ.

The MHEG Centre - general information about MHEG, free MHEG player for Windows and commercial software

MHEG & HyTime: A Comparative Review by Mara Loe Sack Sioe. Presented at Hypermedia '96

PREMO

(ISO/IEC JTC 1/SC 24)
PREMO 'addresses the creation of, presentation of and interaction with all forms of information using single or multiple media.' Presentation Environment for Multimedia Objects. An ISO standard being developed to provide a standardised development environment for multimedia applications. It concentrates mainly on presentation techniques. One of the major goals of PREMO was to be able to integrate different media and their presentation techniques into the same framework. Because new techniques are continually being developed and techniques may be application dependent, PREMO uses an object-oriented approach. This means that existing objects may inherit new knowledge. This allows re-use of objects without having to specify entirely new standards. Since many distributed environments are now widespread, the PREMO specification will allow for the implementation of multimedia services over a network.

PREMO is designed to work with existing and emerging standards. For example it will provide services which can be used to create an MHEG engine - it could be recognised as a PREMO component.

For more information see:
P>PREMO Web Site - documentation and current activities

PREMO - An ISO standard for a presentation environment for multimedia objects (paper)

MIME

The orginal Internet email standards state that the message should be ASCII, no line longer that 1000 characters, and it should not exceed a certain length. As technology has developed this has become restrictive, and a new standard Mime - Multipurpose Internet Mail Extensions - has been developed. This is designed to allow multi-media email between many different systems that use Internet mail standards. Mime message can be of unlimited length, contain multiple objects, contain binary files and allow images, audio, video and multimedia messages to be sent.

A MIME message consists of several parts

  • The MIME-Version header
  • The Content-Type header, which specifies the type of data. This may be
    1. text - the default
    2. image - for still images, defined sub-types are image/gif and image/jpeg
    3. audio
    4. video - defined sub-type video/mpeg
    5. message - to encapsulate a RFC 822 format message
    6. multipart - allows several different types and subtypes to be put in one message body.
    7. application - used for most other kinds of data.
  • The Content-Transfer-Encoding header, which specifies how the data is encoded
  • Two other header fields that identify and describe the data - Content-ID and Content-Description

New sub-types can be defined, including 'private' subtypes, which begin with 'X-'. While a good system will be able to display image, play auido etc, a MIME implementation does not need to support all types, the minimal requirements are mainly that the users are not shown raw date inappropriately.

QuickTime

QuickTime is a proprietory format from Apple. Originally designed for the Mac, it is now supported on several platforms. It is composed of three elements:
  • the movie file format
  • media abstraction layer
  • media services
The movie format is a container format, which can in fact contain any digital media For more information see Apple's Quicktime pages

Graphics     Multimedia      Virtual Environments      Visualisation      Contents