Using MPEG-21 for cross-layer multimedia content adaptation
Résumé
This paper presents a cross-layer model— formulated using interoperable description formats—for the adaptation of scalable H.264/MPEG-4 AVC (i.e., SVC) content in a video streaming system operating on a Wireless LAN access network without QoS mechanisms. SVC content adaptation on the server takes place on the application layer using an adaptation process compliant with the MPEG-21 Digital Item Adaptation (DIA) standard, based on input comprised of MPEG-21 DIA descriptions of content and usage environment parameters. The latter descriptions integrate information from different layers, e.g., device characteristics and packet loss rate, in an attempt to increase the interoperability of this cross-layer model, thus making it applicable to other models. For the sake of deriving model parameters, performance measurements from two wireless access point models were taken in account. Throughout the investigation it emerged that the behavior of the system strongly depends on the access point. Therefore, we investigated the use of end-to-end-based rate control algorithms for steering the content adaptation. Simulations of rate adaptation algorithms were subsequently performed, leading to the conclusion that a TFRC-based adaptation technique (TCP-Friendly Rate Control) performs quite well in adapting to limited bandwidth and varying network conditions. In the paper we demonstrate how TFRC-based content adaptation can be realized using MPEG-21 tools.