MHEG encompasses the family of standards issued by the ISO/IEC JTC1 joint technical committee's working group WG12‹information technology subcommitte SC29, coding of audio, picture multimedia, and hypermedia information. See Table 23.1 for the complete list of MHEG standards.
| Version | Complete Name | Status |
|---|---|---|
| MHEG-1 | MHEG object representation-base | International standard |
| notation (ASN.1) | ||
| MHEG-2 | MHEG object representation-alternate | Withdrawn |
| notation (SGML) | ||
| MHEG-3 | MHEG script interchange representation | International standard |
| MHEG-4 | MHEG registration procedure | International standard |
| MHEG-5 | Support for base-level interactive applications | International standard |
| MHEG-6 | Support for enhanced interactive applications | International standard |
| (April 1998) | ||
| MHEG-7 | Interoperability and conformance testing | Draft international standard |
| for ISO/IEC 13522-5 | (Jan 1999) |
Since it was introduced first, MHEG-1 received the most attention. It's the generic standard for encoding multimedia objects without specific assumptions on the application area or on the target platform used for delivering and rendering these objects to the user. MHEG-3 provides a script extension to MHEG-1. MHEG-4 specifies a registration procedure for identifiers used by the objects to identify, for example, a specific format for content data. MHEG-5 can conceptually be considered a simplifying profile of MHEG-1. It addresses terminals with limited resources, like the set-top unit. Actually, an MHEG-1 decoder can't decode MHEG-5 applications due to some slightly different provisions added to optimize performance in VoD/ITV environments. MHEG-6 extends the declarative MHEG-5 approach with procedural code capabilities typical of a scripting language. It defines the interface (MHEG-5 API) and a script engine's runtime environment on top of an MHEG-5 engine using the Java virtual machine to provide a complete solution for application representation. MHEG-7, a new standard, addresses the conformance and interoperability of MHEG-5 engines and applications.