Digital Object Identifier (DOI) 10.1007/s00530-002-0060-5
Multimedia Systems 8: 395–396 (2002) Multimedia Systems
© Springer-Verlag 2002
Introduction to Multimedia special issue on multimedia middleware
Middleware + multimedia = multimedia middleware?
Thomas Plagemann
Department of Informatics, University of Oslo, P.O. Box 1080, Blindern, 0316 Oslo, Norway
This special issue is based on the Multimedia Middleware
(M3W)Workshopheld at the9thACMMultimediaConference
in Ottawa 2001. The workshop was well attended and charac-
terized by very interactive and constructive discussions. Most
participants stayed in the meeting room even during lunch to
proceed with discussions – and that after three days of the
ACM Multimedia Conference. The success of the workshop
has finally led to this special issue. The authors of the 12
best papers at the workshop have been invited to submit a full
journal paper to compete for publication. Based on the rec-
ommendations of the M3W Program Committee, which did
an excellent job in reviewing all submissions for this special
issue, we present here four papers. These papers describe:
novel solutions for integrated runtime support in QoS-aware
middleware; dynamic end-to-end QoS management middle-
ware; proxy architectures for collaborative media streaming;
and abstractions for multimedia streaming.
The topics of the four papers already indicate the broad
range of research questions that are studied in the context of
multimedia middleware, and readers who refer to the work-
shop’s web page1 will see even more topics of interest for
multimedia middleware. Since the range of topics is so broad,
it is legitimate to ask whether there is actually a clear defini-
tion and scope of multimedia middleware. A straightforward
definition might be that multimedia middleware covers all re-
search topics related to the use of middleware for multimedia
applications. The follow up question for readers familiar with
the meaning of multimedia would probably be: What is mid-
dleware?
A short answer to this question could be that there is no
clear definition. Formany researchers and developers, the term
‘middleware’ is today synonymous with object-based middle-
ware, like the OMG’s CORBA or Microsoft’s DCOM. How-
ever, object-based middleware is only one type of middleware
besides others like event-based and message-oriented middle-
ware. Since multimedia middleware might be seen as another
type of middleware, we refer to a more basic definition of
middleware from Geoff Coulson2:
The role of middleware is to ease the task of designing, pro-
gramming and managing distributed applications by provid-
1 http://www.ifi.uio.no/∼m3w/
2 http://dsonline.computer.org/middleware/index.htm
ing a simple, consistent and integrated distributed program-
ming environment. Essentially, middleware is a distributed
software layer, or ‘platform’ which abstracts over the com-
plexity and heterogeneity of the underlying distributed envi-
ronment with its multitude of network technologies, machine
architectures, operating systems and programming languages.
In other words, abstraction away from complexity and het-
erogeneity is the main goal of middleware. In this context, it
is important to note that multimedia applications increase the
heterogeneity problem. First, there exist many different en-
coding formats for video, audio, graphics, etc. To relieve ap-
plication developers from format considerations, multimedia
middleware should provide services for compatibility control
andmanagement, e.g. implicit transcoding to allow peers with
incompatible media formats to communicate. Secondly, the
QoS requirements of communication partners might be dif-
ferent due to end-user demands or available resources. Multi-
media middleware should thus include QoS management ser-
vices that establish andmaintain (if possible) aQoS agreement
that satisfies all peers [1]. Thirdly, there are already several
QoS solutions at different system levels, e.g. intserv and diff-
serv networks, adaptive CPU schedulers, self-adapting video
players, and QoS aware Object Request Brokers. The reuse
of existing QoS solutions and their combination and integra-
tion in a single session requires a solution to this particular
type of heterogeneity problem. Thus, Ecklund et al. describe
in this special issue a dynamic end-to-end QoS management
middleware platform that addresses this problem and shows
how legacy QoS solutions can be integrated.Another problem
addressed in this paper is the dynamic nature of sessions. The
application structure as well as the configuration of the system
can be changed during an ongoing session. Consequently, the
QoSmanagement structure has to be adapted accordingly, and
is therefore dynamic.
To manage QoS and get at the application level informa-
tion about the system state to improve application adaptation,
openness of the system and control over the system are nec-
essary. In addressing these needs, Baochun et al. present an
integrated runtime QoS-aware middleware framework. This
is designed to provide runtime support for all stages of QoS