The MPEG Video Standards – from 1 to 21

MPEG4 – Internet Streaming and Synchronized Multimedia
Where MPEG2 was designed to scale up to broadcast and high-definition quality and operating requirements, MPEG4 goes the other way. It's designed to scale down – down to dial-up internet bandwidths and to tiny devices like cell phones and PDAs; as well as still remain viable for high-quality desktop streaming up to 1Mbps. MPEG4's AAC audio codec is the root of the MP4 file type, recently popularized by Apple's iTunes, among others.

But MPEG4 is much more than just an audio and video compression/decompression scheme. It's a container for all kinds of media objects (images, text, video, animation, interactive elements like buttons and imagemaps, etc) and a way to choreograph them into a synchronized, interactive presentation. (see Interactive Authoring for MPEG4 for more info). MPEG4 also has standard interfaces to allow plugging in a DRM scheme called Intellectual Property Management and Protection (IPMP).

MPEG4 is still at the frontier of media technologies. The specification is extensive, and each vendor implements it in their own way. Try a variety of MPEG4 tools and you'll find lots of incompatibilities. But some are working to smooth the landscape. The Internet Streaming Media Association (ISMA) is an industry consortium dedicated to interoperability among MPEG4 products and services. Essentially, any implementation that's ISMA-compliant will work with any other.

MPEG7
MPEG7 is not a video or audio coding scheme or delivery mechanism. It's about metadata. In a world of more and more content stored in more places, the ability to identify, search, index, and publish information about content is key. Officially called the Multimedia Content Description Interface, it's a set of rules and tools for describing content.

Most media file types already can carry a metadata payload, which is typically used for Title, Artist, and Copyright information. MPEG7 is like that...and then some. Complex and customized metadata structures can be defined using the XML-based Description Definition Language (DDL). Metadata schemes can include descriptions of semantic elements (i.e. shapes, colors, people, objects, motion, musical notation); catalog elements (copyright and access rules, parental ratings, title, location, date, etc); or structural elements (technical stats about the media). Search engines, PVRs, live broadcasts and content management systems all can benefit from a standard, human- and machine-readable way to describe and identify content.