Adaptive delivery of video data over wireless and mobile environments

As pervasive computing is becoming a reality that has already begun to shape our lives, the need for multimedia delivery systems in wireless and mobile environments is direr. The richness of multimedia data, the limitations of the wireless networks, and the restrictions imposed by the portable device modalities give rise to a complex problem that is in need of immediate solutions. The Moving Picture's Experts Group (MPEG) has started work on a new standardization effort called the "Multimedia Content Description Interface," also known as MPEG-7. The goal of MPEG-7 is to enable fast and efficient searching and filtering of audio-visual material. The effort is being driven by specific requirements gleaned from a large number of applications related to image, video and audio databases, media filtering and interactive media services (radio, TV programs), scientific image libraries, and so forth. Recently, multimedia content description information for enabling Universal Multimedia Access (UMA) has been proposed [1], as part of the MPEG-7 specifications. The basic idea of universal multimedia access (UMA) is to enable client devices with limited communication, processing, storage and display capabilities to access rich multimedia content [5]. The use of MPEG-7 with UMA descriptors would be ideal for our efforts towards fast and efficient multimedia data transmission. In this paper we propose a conceptual model for describing the network conditions under which the multimedia data is being transmitted, as well as the modality of the device which receives the data. We present an architecture for adaptation of multimedia data to such wireless network conditions and device capabilities, under constraints imposed by user preferences and multimedia content, to ensure effective, meaningful, and acceptable delivery of video data to mobile users. The adaptability is achieved through careful application of a combination of off-line and on-line reductions to the video streams. In doing so, we make use of the concept of descriptor schemes for describing the content of video data, and its lendability to different kinds of reductions [1]. In addition to the architecture and the test bed implementation, we also examine a real implementation of this system on a real mobile device. The architecture consists of an MPEG-7 server in the fixed network, and an MPEG-7 player on the mobile host. In addition, an encoder/decoder layer is used to perform physical frame bit reductions on transcoded video frames. The server also maintains index structures and a programmable two-dimensional matrix of reductions. An offline packager module is included with the server, which packages all the MPEG-7 data with the video when the video is first registered with the database.