About MPG, MPEG-4

"Em-peg" Motion Picture Experts Group, compression/decompression (codec) format for storing video and audio on digital media. It was adopted by International Standards Organization as ISO 11172 standard. It is based on a DCT (discrete cosine transform) algorithm. Supported by Apple (MacOS), Microsoft (Windows), Digital Equipment Corp's Alpha PCs, IBM (OS/2), and others.

Unlike Cinpak or Indeo, MPEG is a more than just a codec. It is a complete file format which specifies the arrangement of video and audio that is also different from the audio-video interleave schemes of QuickTime and Video for Windows.

Primarily it compresses the redundant information between frames, such as a background that does not change into one I-frame (compressed intraframe)&emdash;plus any changes to the background. Because of this, MPEG images are difficult to edit. One solution is to decompress the MPEG video; then compress it into Motion-JPEG for editing after which it can be recompressed under MPEG. (MPEG supports higher quality images than Motion-JPEG.) Player utility: Xing MPEG (Windows).

What are MPEG-1 and MPEG-2?

MPEG-1 is a standard that defines compression at data rates typically up to about 1.5 megabits per second (Mbps). It is used extensively today for video CD encoding. MPEG-2 is the standard upon which digital television, set-top boxes and DVDs are based. Work on the MPEG-4 specification started in 1993, and has diverged greatly from its predecessors, MPEG-1 and MPEG-2.

What are the main areas of development in the MPEG-4 standard?

There are many core areas in the MPEG-4 standard including:

· Video. Defines video decoding for rendering and playback. To date, MPEG-4 has specified four different versions for video compression, defining capabilities grouped into 19 distinct "profile" groupings with various "level" degrees in each.

· Audio. Defines audio decoding for rendering and playback. MPEG-4 defines several audio codecs, including MPEG-4 AAC, multiple speech codecs, and synthetic audio.

· File format. Defines the file "container" and how information is organized at the byte level in stored files. The MPEG-4 (MP4) file container is based on but not compatible with Apple QuickTime.

· Profiles and levels. Specifies sets of capabilities and defines data representation format, video resolution, and content delivery data rates among other things. The specifications also define interoperability among vendor products.

· Transport protocols. Defines how content is delivered over networks. MPEG-4 and other standards initiatives define a variety of networking protocols.

· Digital rights management. The MPEG-4 initiative does not have DRM defined today but it does have "hooks" to proprietary DRM systems.

· Other areas. The MPEG-4 specification also defines other areas such as object-based video coding, hybrid coding of synthetic and natural content, face animation parameters, synthetic audio, Binary Format for Scenes (BIFS), and other such features.

What are MPEG-7 and MPEG-21?

The MPEG-7 specification, formally named "Multimedia Content Description Interface", provides a set of standardized tools to describe digital media content, or metadata.

The MPEG-21 specification defines an end-to-end framework outlining all the pieces of a standards-based system—from content creation to delivery to playback. Work is underway in MPEG-21 to define standards-based DRM.

Is the quality of MPEG-4 video competitive with the state of the art?

To be competitive, MPEG recognizes that its video codec must be improved and has launched a video coding project with the goal of adding a new codec design to the MPEG-4 standard to "extend MPEG-4 with state-of-the-art technology" by the spring of 2003. For more information about MPEG's codec quality viewing test, see the MPEG committee document N4240.

Can products based on MPEG-4 provide a complete end-to-end solution for streaming applications?

Currently, products that are based on MPEG-4 cannot provide an end-to-end streaming solution. MPEG-4 lacks some significant features, such as DRM and screen compression, and does not define a fully standard means of providing services such as video over IP streaming. For this reason, implementers of MPEG-4 often choose to add their own features and write additional specifications to enable richer solutions for their customers.

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