Accessing SMIL-based Dynamically Adaptable Multimedia Presentations from Mobile Devices Robert Steele Marcin Lubonski Yuri Ventsov Elaine Lawrence University of Technology, Sydney University of Technology, Sydney University of Technology, Sydney University of Technology, Sydney rsteele@it.uts.edu.au marcin@it.uts.edu.au ventsov@it.uts.edu.au elaine@it.uts.edu.au Abstract Current business presentations are commonly multimedia-based and with the realization of the mobile enterprise, accessing of such presentations stored on servers from mobile devices will become increasingly common. However as a roaming mobile device user moves, factors that change include the local wireless network technology, the available bandwidth, the currently closest source of the media files and even the continuity of wireless access. The XML-based standard, Synchronized Multimedia Integration Language (SMIL), provides a format to specify the display sequence and layout of media files in a multimedia presentation. In this paper we present a SMIL-based system for mobile devices that is able to dynamically adapt presentations in response to such changing mobile computing-related factors as those given above. 1. Introduction As a mobile device user moves a number of factors change that can affect their access to a multimedia presentation. Firstly, the server that is currently the closest or fastest from which to access a multimedia file from may change. As such, ideally, in order to improve network performance a mobile device should change its access source during a presentation to choose the most efficient multimedia source. Secondly, the speed of wireless access may change. For example a device may pass from a Wi-Fi [11] or Bluetooth [1] area into an area with just GPRS [6] access. As bandwidth changes the same sized multimedia files may not be able to be delivered to the mobile device. Thirdly, a mobile device may pass out of wireless communication completely so it will need to adapt to this scenario also. A final problem is that a complete multimedia presentation may be too large to store in its entirety on a mobile device and hence will need to be downloaded and viewed incrementally. 2. Background Synchronized Multimedia Integration Language (SMIL) (pronounced smile) [3] is an XML-based [2, 4, 9] standard. XML provides a customizable format for specifying meta-information about data. Its textual nature makes it human readable and also easy to process and manipulate. XML is also well-suited to communication in mobile computing systems [10] due to the high heterogeneity of such systems and the platform independence of XML. SMIL can be used to provide meta-information about multimedia presentations (see Figure 1). It can be employed by Web site creators to specify how multimedia elements (video, sound, still images) can be presented and played in sequence/ parallel as part of a Web presentation. Table 1 lists the advantages implied by various SMIL features. Because SMIL allows for the sending of multiple movies, still images, and sound separately in a coordinated fashion the researchers believe its flexibility is well suited to the dynamic aspects of mobile computing. Each media object is accessed with a unique Uniform Resource Locator (URL), which means each can be retrieved from a different source and different sources can be used as time moves forward. The methodology used in this research considers two alternatives for delivering a multimedia presentation to a mobile device: as a monolithic multimedia file or as a SMIL-based presentation. We identify the assumed mobile computing architecture (combination of e.g. WiFi and GPRS connectivity), identify aspects of this architecture that effect the access of multimedia presentations from mobile devices and devise new techniques that make use of SMIL to improve such access to multimedia presentations. We consider how these new techniques compare with a monolithic multimedia file- based approach.