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The evolution of technologies in the area of both telecommunication
and multimedia have significantly contributed to the emergence of
new multimedia applications. Those applications integrate various
media types, such as text, graphics, audio and video, which
typically possess timeliness requirements with respect to their
presentation. Media synchronization mechanisms are needed to assure
the correct temporal alignment of such time-critical activities. Two
levels of multimedia synchronization can be distinguished,
continuous synchronization and event-based synchronization. While
the first one aims at the synchronized play-out of data streams, the
latter ones orchestrates the presentation of possibly distributed
multimedia objects. Multimedia objects may consist of a variety of
timely related subobjects, such as video clips, audio, text
fragments and images. If a multimedia object contains continuous
media, object synchronization comprises stream synchronization at a
lower level of abstraction. In other words, stream synchronization
functions form the basis for synchronization mechanisms operating at
the object-level. In the remainder of this paper, we will focus on
stream synchronization functions. The next section, gives a brief
classification of the various approaches existing in this field.
Then, in Sec. 3, we will describe the principles and properties of
the Adaptive Synchronization Protocol (ASP), which has been
developed in the CINEMA project [RBH94]. Finally, we will conclude
with a brief summary.
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