Abstract—The information revolution of the last decade has
resulted in a phenomenal increase in the quantity of multimedia
content available to an increasing number of different users with
different preferences who access it through a plethora of devices
and over heterogeneous networks. In order to encounter the
amount of different content types, MPEG-21 Digital Item
Adaptation (DIA) introduces interoperable description tools
which enable coding format independent adaptation. Bandwidthefficient
transport of the content to terminals with different
capabilities and through a variety of access networks with
various characteristics requires adaptation facilities not only on
the server but also within the network. In this paper we present
transport mechanisms for MPEG-21-based metadata enabling
generic adaptation within the network. Three different transport
mechanisms for delivering this metadata in conjunction with the
corresponding multimedia content are evaluated and a payload
format for the transport of this metadata is presented.
Furthermore, we performed measurements which demonstrate
the bandwidth benefits of our distributed adaptation approach
compared to server-centric adaptation in a multicast scenario.
Finally, we applied various encoding formats for the metadata
which further reduces the metadata overhead.

Keywords—MPEG-21 Digital Item Adaptation; distributed
multimedia adaptation; metadata transport