MPEG4

Unlike MPEG1 and MPEG2 which had one clear application in mind when they were developed, MPEG4 is a much broader umbrella-type standard. Initially it was aimed at very low bitrate communications, however its scope was expanded to be much more of a multimedia coding standard. The additional functionalities of MPEG4 include [Tal98]:

• The ability to efficiently encode mixed media data, such as video, graphics, text, images, audio, and speech, with the introduction of the audiovisual objects concept.
• The ability to create a compelling multimedia presentation by composing these mixed media via scripts.
• Error resilience through content-based scalability, resynchronisation, data partitioning, reversible variable length codes, and header extension codes, discussed in Chapter 4.
• The ability to encode arbitrarily shaped video objects.
• Multiplexing and synchronisation of the data associated with these objects, so that they can be transported according to Quality of Service (QoS) constraints over networks.
• The ability to interact with the audiovisual scene generated at the receiver end.

These functionalities, are specified in an open toolkit approach, allowing for the incorporation of emergent coding algorithms. Applications will be able to select and download additional tools as required.

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