Internet Delivery of MPEG-4 Object-Based Multimedia

T he advent of object-based multime-dia standards, in particular MPEG-4, has brought new challenges to the subject of media streaming over the Internet. To tackle these challenges, the Moving Picture Expert Group (MPEG) defined a generic multimedia delivery platform—the Delivery Multimedia Integration Framework—under the MPEG-4 umbrella. In this article we describe the DMIF framework and examine several remote retrieval issues related mostly to the successful multiplexing, delivery, demultiplexing, (re)syn-chronization, and eventually, playback of multi-media object streams at the client. We then describe our design and implementation of a DMIF-based MPEG-4 streaming system. In order to verify the specifications of MPEG-4, the MPEG-4 committee 1 initiated an implementation effort to produce IM1, the reference software for MPEG-4. Our implementation has become part of IM1, which implements the compression and systems layers of MPEG-4. Our additions to IM1 include the implementation of a DMIF instance for remote retrieval and an MPEG-4 streaming server that fully supports DMIF. Although other researchers 2 have reported similar efforts to produce the DMIF instance for remote retrieval, the results of those efforts aren't available to the public or MPEG community for verification. Also, we're not aware of any published work that reported the implementation details DMIF. Our implementation provides the first open source code for this part of the DMIF standard. The MPEG-4 standard is a novel multimedia technology that encompasses a wide range of tools and technologies. Unlike its predecessors (MPEG-1 and MPEG-2), the MPEG-4 standard doesn't focus only on the media compression aspect of multimedia technology. It also considers the media packaging and delivery parts and many of the tools that future multimedia applications might need. Other than being a comprehensive multimedia standard, MPEG-4 has a more interesting feature: it's an object-based multimedia technology. An MPEG-4 presentation comprises units of aural, visual, or audiovisual content, called media objects. These objects can be of natural origin, such as camera-generated images, or synthetic origin, such as computer-generated images or voice. Being object-based, MPEG-4 enables many new applications. Interactive multimedia, scene manipulation, and controlling individual objects are just some of the features that MPEG-4 provides. Figure 1 depicts an example of an MPEG-4 audiovisual scene. Coding, composition, and streaming of media objects Media objects in an MPEG-4 audiovisual scene can be still images (a fixed background), video objects (a talking person without the background), audio objects (the voice associated with the talking person), and so on. In …