Overview Of Mpeg-4 - MULTIMEDIA

MPEG - 4 is an ISO / IEC standard developed by MPEG (Moving Picture Experts Group), the committee that also developed the Emmy Award winning standards known as MPEG - 1 and MPEG - 2. These standards made interactive video on CD - ROM, DVD and Digital Television possible. MPEG - 4 is the result of another international effort involving hundreds of researchers and engineers from all over the world. MPEG - 4, with formal as its ISO / IEC designation 'ISO / IEC 14496', was finalized in October 1998 and became an International Standard in the first months of 1999. The fully backward compatible extensions under the title of MPEG - 4 Version 2 were frozen at the end of 1999, to acquire the formal International Standard Status early in 2000. Several extensions were added since and work on some specific work - items work is still in progress.

MPEG - 4 builds on the proven success of three fields:

  • Digital television;
  • Interactive graphics applications (synthetic content);
  • Interactive multimedia (World Wide Web, distribution of and access to content)

MPEG - 4 provides the standardized technological elements enabling the integration of the production, distribution and content access paradigms of the three fields.

The MPEG - 4 standard provides a set of technologies to satisfy the needs of authors, service providers and end users alike.

  • For authors, MPEG - 4 enables the production of content that has far greater reusability, has greater flexibility than is possible today with individual technologies such as digital television, animated graphics, World Wide Web (WWW) pages and their extensions. Also, it is now possible to better manage and protect content owner rights.

  • For network service providers MPEG - 4 offers transparent information, which can be interpreted and translated into the appropriate native signaling messages of each network with the help of relevant standards bodies. The foregoing, however, excludes Quality of Service considerations, for which MPEG - 4 provides a generic QoS descriptor for different MPEG - 4 media. The exact translations from the QoS parameters set for each media to the network QoS are beyond the scope of MPEG - 4 and are left to network providers. Signaling of the MPEG - 4 media QoS descriptors end - to - end enables transport optimization in heterogeneous networks.

  • For end users, MPEG - 4 brings higher levels of interaction with content, within the limits set by the author. It also brings multimedia to new networks, including those employing relatively low bitrate, and mobile ones. An MPEG - 4 applications document exists on the MPEG Home page, which describes many end user applications, including interactive multimedia broadcast and mobile communications.

For all parties involved, MPEG seeks to avoid a multitude of proprietary, non - interworking formats and players.

MPEG - 4 achieves these goals by providing standardized ways to:

  1. Represent units of aural, visual or audiovisual content, called “media objects”. These media objects can be of natural or synthetic origin; this means they could be recorded with a camera or microphone, or generated with a computer;
  2. describe the composition of these objects to create compound media objects that form audiovisual scenes;
  3. multiplex and synchronize the data associated with media objects, so that they can be transported over network channels providing a QoS appropriate for the nature of the specific media objects; and
  4. interact with the audiovisual scene generated at the receiver’s end.

Composition and manipulation of MPEG - 4 videos (VOP = Video Object Plane)

Composition and manipulation of MPEG - 4 videos (VOP = Video Object Plane)

The hierarchical structure of JPEG - 4 visual bitstreams is very different from that of MPEG - 1 and 2 in that it is very much video - object - oriented. In general, each Video - object Sequence (VS) will have one or more Video Objects (VOs), each VO will have one or more Video Object Layers (VOLs), and so on. Syntactically, all five levels have a unique start code in the bitstream, to enable random access.

  1. Video object sequence (VS). VS delivers the complete MPEG - 4 visual scene, which may contain 2D or 3D natural or synthetic objects.

  2. Comparison of interactivities in MPEG standards: (a) reference models in MPEG - 1 and 2 (interaction in dashed lines supported only by MPEG - 2); (b) MPEG - 4 reference mddel

    Comparison of interactivities in MPEG standards: (a) reference models in MPEG - 1 and 2 (interaction in dashed lines supported only by MPEG - 2); (b) MPEG - 4 reference mddel

    Comparison of interactivities in MPEG standards: (a) reference models in MPEG - 1 and 2 (interaction in dashed lines supported only by MPEG - 2); (b) MPEG - 4 reference mddel

  3. Video Object (VO). VO is a particular object in the scene, which can be of arbitrary (nonrectangular) shape, corresponding to an object or background of the scene.

  4. Video Object Layer (VOL). VOL facilitates way to support (multilayered) scalable coding. A VO can have multiple VOLs under scalable coding or a single VOL under

Video = object - oriented hierarchical description of a scene in MPEG - 4 visual bitstreams

object - oriented hierarchical description of a scene in MPEG - 4 visual bitstreams

nonscalable coding. As a special case, MPEG - 4 also supports a special type of VOL with a shorter header. This provides bitstream compatibility with the baseline H.263.

  • Group of Video object planes (GOV) groups video object planes. It is an optional level.
  • Video Object plane (VOP). A VOP is a snapshot of a VO at a particular moment, reflecting the VOs shape, texture, and motion parameters at that instant. In general, a VOP is an image of arbitrary shape. A degenerate case in MPEG - 4 video coding occurs when the entire rectangular video frame is treated as a VOP. In this case, it is equivalent to MPEG - 1 and 2. MPEG - 4 allows overlapped VOPs - that is, a VOP can partially occlude another VOP in a scene.

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