One of the most important standardization efforts in the broad field o
f audio-visual coding is MPEG-4 which introduces objects as smallest a
ccessible units inside frames. This conceptual step forward led to com
pletely new possibilities for applications using content-based scalabi
lity or content-based interactivity. When MPEG-4 started in 1994 it wa
s no more than an ambitious vision. Then, in March 1998, it received t
he status of the final committee draft of an international standard an
d it is certainly a milestone in realizing second-generation audio-vis
ual communication systems. In this paper, we give a brief introduction
to MPEG-4 systems terminology and discuss the set-up procedure of an
application using MPEG-4 systems. We present a prototype implementatio
n of a video-on-demand application that enables distributed event hand
ling of object-related events created by a user. Our system consists o
f a client/server architecture, where the client side handles events l
ike zooming or moving single video objects at presentation time, while
the server side manages user control concerning the quality of a loss
y encoding of the single video objects. The system is introduced by me
ans of OMT diagrams, status diagrams and block diagrams. (C) 1998 Else
vier Science B.V. All rights reserved.