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"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.
Original text: http://www.xvsonline.com/xfiles/about_mpg.htm
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