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.