MPEG-4 IS BEING DEVELOPED UNDER THE AEGIS of the Motion Pictures Experts Group, an expert body within the International Standards Organization (ISO). This is the same group that developed the MPEG-1 and MPEG-2 standards. MPEG-1 galvanized the growth of the Video CD industry. The MPEG-1 Layer 3 audio coding format, familiarly known as MP3, is the audio coding format of choice for music downloads.

The MPEG-2 set of standards, developed in 1992, sparked a digital revolution in the broadcast space. This standard was adopted worldwide for the broadcast delivery of digital television content. Today's satellite networks as well as the digital cable networks are based on MPEG-2 standards. The DVD video standard is based on the MPEG-2 video standards.

MPEG began the process of developing the process of evaluating the technologies necessary to support the encoding of high-definition video content. This was to be the MPEG-3 set of standards. During the evaluation process, it was discovered that the technologies encompassed in MPEG-2 were sufficient to satisfy the requirements for the encoding and delivery of HD content. Thus, the MPEG-3 standardization process was stopped and MPEG-2 has been the technology of choice for digital television eversince.

MPEG-4: An Introduction
MPEG-4 is more than just an audio/video standard. By embracing the concepts of object based coding and incorporating the coding of 2D and 3D objects, animation, text, interactivity and more, it expanded the scope of applications that may be addressed by the set of tools encompassed in its specifications. Aspects such as object-based coding, compression efficiency, universal access, user interaction, intellectual property management and protection, programmatic interfaces, and multi-user interactions are all part of the standard.

The basic principle is that an audio-visual scene consists of individual audio-visual objects composed for presentation-based, on-the-scene description information. The scene description information consists of the presentation information for each of the audio-visual objects. To give an example, the presentation information for a video object may consist of its spatial location and the size of the presentation window. In addition, the scene description also encapsulates the “interactivity” information. The sensor nodes and the ROUTE mechanisms provide the necessary hooks to describe the desired interactivity between the user and the scene as well as between the various objects within a scene.

MPEG-4’s object-orientation creates a framework for adding interactivity to scenes as each object can be enabled with unique functionality.

The MPEG-4 Payoff
Increased Compression Efficiency: The video and audio compression algorithms provide more compression efficiency than previous compression algorithms. The MPEG-4 video compression algorithms have improved on the previous algorithms by a significant factor. This implies that for delivering the same quality, the MPEG-4 video compression algorithms consume fewer bits than the other compression algorithms.

Heterogeneous Media Types: MPEG-4 provides the framework to address applications from those that contain simple video and audio content to those that have fully integrated interactive rich multimedia content. The latter set of applications may contain, in addition to video and audio, rich 2D and 3D graphical elements, text as well as elements of user interaction (content selection, scene navigation, enhanced electronic program guides, etc.). The picture shown gives an example of a screen layout of such a program.

Heterogeneous Environments: Delivery and Presentation: With the proliferation of wired and wireless networks, the content creator today is not really aware of how his or her content is accessed and eventually delivered to the customer. However, he (or she) would want their creation to be experienced in a manner as consistent with their vision. The separation of description and presentation is a powerful one. The flexibility in being able to deliver the data over a diversity of networks is particularly appealing to the content creators and content providers. Towards achieving interoperability across the producer-consumer chain, standards for packetization and delivery of MPEG-4 contents over standard cable networks as well as IP-based networks are in various stages of development and testing. Given the proliferation of presentation devices (cell phones, PDAs, PCs, set top boxes) and environments (enterprise, home, roaming), it is also expected that the MPEG-4 set of technologies will be leveraged to enable content flow seamlessly across these networks to these end devices.

The Application Space
In contrast to the MPEG-2 set of technologies, MPEG-4, in addition to increased coding efficiencies in video and audio also provides for scene arrangement. Some of the application spaces are outlined in the following sections. The discerning user realizes that the look-and-feel.

Rich Multimedia Content: In contrast to traditional television, MPEG-4 offers the opportunity to present a rich mix of video, audio, graphics, and text. A screenshot of such a multimedia presentation is shown in Figure 1. The figure indicates an arrangement of multiple videos along with a main video. Interaction with the scene elements is facilitated by the placement of "buttons" in the scene. In the example in Figure 1, the buttons indicating up and down arrows are used to scroll through the preview video windows. The buttons on the right of the screen control the playback of the audiovisual content in the main window. In this particular presentation, the end user also has the option of projecting the video in the main window over the entire screen. In addition to the regular audiovisual programs, the scene layout also allows for the placement of advertisements and text information, as indicated in the figure.

Interactive Television: An application enabled by the MPEG-4 technologies is interactive television. The screen shot shown in Figures1 and 2 are germane to this discussion. The underlying technologies (scene description formats, media encodings, etc) are the same. It is quite conceivable that the scene layout as indicated in Figure 1 may function as a portal to services a-la Figure 2. The user, after finishing with watching the movie (or program) may "navigate" back to the user guide (Figure 1) to find out what else is available or is showing at the moment.

Other applications: It is expected that with the deployment of the full power of MPEG-4, a whole plethora of applications be will magically enabled. The DVD navigator look-and-feel (see Figure 2, for instance) is now a simple extension of the rich multimedia content. The look-and-feel is now a part of the content and may be tailored according to the delivery or presentation environment. This look-and-feel is now not restricted to packaged media alone but may also be streamed.

Content Creation: Given that the scene composition and rendering is now done on the presentation, the precise description of object layout and interaction is very critical. Content creators may perhaps desire the end users have some license in personalizing the look-and-feel on their presentation devices. Content creators may also want their contents to play “as best as possible” on a variety of presentation devices. Given some of these constraints, the complexity of content creation is now increased multifold. Creation of good content is now gated by the availability of easy-to-use and yet powerful authoring tools. Stay tuned—authoring tool vendors are expected to announce support for MPEG-4 in their respective offerings soon.

More in the Pipeline
The MPEG-4 standards are not quite done. There are a few more projects in the pipe that are expected to reach maturation in the next few months. A couple are outlined in the following sections. The reader is urged to navigate to one of the sites given in the last section.

Advanced Video Coding: MPEG and ITU have been working together the last two years towards a common video compression standard. Known variously as H.26L, H.264, JVT, MPEG-4 Part 10, this specification is expected to reach International Standard within both the MPEG and ITU bodies sometime towards the first half of 2003. Tests indicate that this video compression scheme may provide almost 2-4 times the compression obtained using the MPEG-2 standards and is more efficient than the existing MPEG-4 schemes. At this stage, the computational complexities associated with the encoding and decoding are yet a bit high. This is not expected to be an issue in another two years given that the complexities in integrated circuits keep increasing with every revision. Digital signal processors from Texas Instruments, Philips and Equator Technologies are becoming more sophisticated with increased hardware support for specialized modules that aid in fast video encoding and decoding.

Intellectual Property Management and Protection (IPMP): MPEG has recognized that, along with facilitating the creation of high-value content, it is important to keep in mind that the delivery and usage of such content requires a good DRM framework in place that ensures the appropriateness of that usage. Given that, MPEG began with defining hooks (MPEG-2, MPEG-4) to incorporate proprietary DRM systems into the MPEG framework. From there, MPEG is moving towards a more encompassing standardization of the IPMP framework with the goal of interoperability. From the consumer's point of view, this requires ensuring that content from multiple sources will play on players from different manufacturers. From a manufacturer's point of view, it is important that the modules from different suppliers can be integrated in a product through clear interface agreements. These have been the focus of the IPMP work activities in MPEG.

Industry Adoption
Over the last couple of years, the multimedia industry has become a whole lot more knowledgeable about the MPEG-4 and its potential to influence the next generation of interactive digital television. With the convergence of the PC and the TV, the impetus to create and deliver content that is able to transcend the dichotomy of these two extremes is rather large.

Companies have built their product suites based on the MPEG-4 technologies, including the MPEG-4 Systems. Apple's Quicktime 6 release supports the decoding of MPEG-4 video and audio content. It is hoped that the support for MPEG-4 Systems will soon follow. Fraunhoffer (FhG) (www.iis.fhg.de) has always been at the forefront of digital audio. They, along with Dolby Corp. (www.dolby.com), have been strong proponents of MPEG-4 AAC audio.

MPEG-4 video has found a foothold in the wireless industry. The 3GPP consortium (www.3gpp2.org) has agreed on one of the profiles of MPEG-4 video (ISO/IEC 14496-2) as the standard for video content. PacketVideo Corp. and Emblaze Inc, among others, have been at the forefront of developing technologies for the delivery of MPEG-4 video over wireless cellular networks. In Japan, digital cellular trials have involved the delivery of MPEG-4 video over cellular networks. With several companies announcing plans to release ASICs for hardware video and audio encoding, the development of set top boxes that support MPEG-4 in their framework is now picking up speed. Reference set top box designs and implementations are being made available and the general expectation is that MPEG-4 is well on its way to worldwide deployment.