Transport mechanisms for metadata-driven distributed multimedia adaptation

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 and who access it through a plethora of devices and over heterogeneous networks. In order to address the amount of different content types, MPEG-21 digital item adaptation (DIA) introduces interoperable description tools which enable coding format independent adaptation. Bandwidth-efficient 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. 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. 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.