D. Van Deursen

XML to RDF Conversion: A Generic Approach

The role of metadata is gaining importance due to todays growth of multimedia content. Currently, XML is the standard for data interchange. However, as XML Schemas do not express semantics but rather the document structure, there is a lack of semantic interoperability regarding current (XML-based) metadata standards. By using semantic Web technologies, ontologies can be created to describe the semantics of a particular metadata format. A problem is that the existing XML data (compliant with a particul.ar metadata format) cannot be used by an ontology, implying the need for a conversion of XML data to RDF instances. In this paper, a generic approach is proposed for the transformation of XML data into RDF instances in an ontology-dependent way. By means of a mapping document, the link is described between an XML Schema (describing the structure of particular XML data) and an OWL ontology. Our approach is illustrated by applying it to the DIG35 specification, which is an XML-based metadata standard for the description of digital images.

Enhanced Shot-Based Video Adaptation using MPEG-21 generic Bitstream Syntax Schema

Semantic video adaptation takes into account the relevance of the different fragments of the video content in order to create a tailored video stream based on the users preferences. As a shot can be considered as the smallest semantic unit in a video sequence, metadata can be added to each shot using MPEG-7 descriptions. Based on these metadata and the users preferences, the original bitstream can be adapted in order to obtain the desired fragments. MPEG-21 DIA offers a tool, gBS schema, for exposing the high-level structure of a binary resource as an XML description. In this paper, shot information is inserted in these descriptions to create a link between metadata and semantic video adaptation. Furthermore, this paper proposes to keep the structure of these descriptions format-agnostic. As a result, only one generic transformation style sheet has to be implemented to support shot-based video adaptation of sequences compliant with different video specifications. Special attention is paid to sequences coded with the H.264/AVC standard as this specification contains several interesting features important for shot-based video adaptation

On an Evaluation of Transformation Languages in a Fully XML-Driven Framework for Video Content Adaptation

Bitstream structure descriptions (BSDs) allow taking the complexity of transforming scalable bitstreams from the compressed domain to the semantic domain. These descriptions are an essential part of an XML-driven video adaptation framework. The performance of a BSD transformation engine is very important in such architecture. This paper evaluates the efficiency of XML-based transformation languages in our video adaptation framework. XSLT, STX, and a hybrid solution are compared to each other in terms of execution times, memory consumption, and user-friendliness. Our experiments show that STX is the preferred solution when speed and low-memory are important. The hybrid solution is competitive in terms of memory consumption and is more user-friendly than STX. Although XSLT is relative fast, its memory consumption is very high

MuMiVA: A Multimedia Delivery Platform Using Format-Agnostic, XML-Driven Content Adaptation

Due to the increasing heterogeneity in the current multimedia landscape, the delivery of multimedia content has become an important issue today. This heterogeneity is not only reflected by a plethora of different usage environments, but also by the presence of multiple (scalable) coding formats. Therefore, format-independent adaptation engines have to be used within a multimedia delivery platform, which are able to adapt the multimedia content according to a certain usage environment, independent of the underlying coding format of the content. By relying on automatically created textual descriptions of the high-level syntax of binary media resources, a format-independent adaptation engine can be built. MPEG-21 generic bitstream syntax schema (gBS schema) is a tool that is part of the MPEG-21 multimedia framework. It enables the use of generic bitstream syntax descriptions (gBSDs), i.e., textual descriptions in XML, to steer the adaptation of a binary media resource, using format-independent adaptation logic. In this paper, we address the design and performance evaluation of a multimedia delivery platform that relies on gBS schema-driven adaptation engines. Our platform is called MuMiVA; it is a fully integrated, extensible platform for multimedia delivery in heterogeneous usage environments, using streaming technologies. To demonstrate the flexibility of our multimedia delivery platform, we discuss the functioning of two different applications (i.e., exploitation of temporal scalability and shot selection) applied to two different coding formats (i.e., MPEG-4 visual and H.264/AVC).

NinSuna: A Format-Independent Multimedia Content Adaptation Platform Based on Semantic Web Technologies

Multimedia content adaptation is gaining importance because of the growing amount of multimedia content on the one hand and the growing diversity in usage environments on the other hand. Furthermore, to deal with the growing amount of coding formats for multimedia content, format-independent adaptation systems are desired. These systems support the exploitation of scalability to meet the usage environment, as well as semantic adaptations to meet the user preferences. In this demonstration, we present NinSuna, a fully integrated multimedia content adaptation platform based on semantic web technologies. It aims at being deployable in streaming environments and relies on format-independent semantic-aware adaptation engines.

Automatic generation of generic Bitstream Syntax Descriptions applied to H.264/AVC SVC encoded video streams

In order to create a media resource adaptation engine that supports current and future coding formats, a generic (i.e., format-agnostic) solution is needed. One way to realize this is to rely on automatically created textual descriptions of the high-level syntax of binary media resources, which can be used to steer the adaptation of media resources. MPEG-21 generic bitstream syntax schema (gBS Schema) is a tool that enables the use of format-agnostic textual descriptions or generic bitstream syntax descriptions (gBSDs). This paper introduces gBFlavor, a novel solution for the automatic generation of gBSDs. It offers the possibility to automatically generate a format-specific parser that is able to produce a gBSD for a given media resource. In this paper, the use of gBFlavor is demonstrated for the generation of gBSDs for H.264/AVC SVC compliant bitstreams. Performance results show that the proposed solution outperforms existing techniques in terms of execution speed.

XML-based Exploitation of Region of Interest Scalability in Scalable Video Coding

The use of Regions Of Interest (ROIs) is a useful concept for many application scenarios, especially for those applications that are deployed in heterogeneous multimedia environments. In this paper, we show how Flexible Macroblock Ordering can be used in the scalable extension of the H.264/AVC specification in order to define the ROIs in the coded bit- stream. Furthermore, we introduce an XML-driven adaptation framework based on the MPEG-21 Bitstream Syntax Description Language in order to implement the ROI extraction process. This framework gives us the opportunity to adapt scalable bitstreams by using an engine that has no knowledge of the underlying coding format. From the performance analysis of our adaptation framework, we can conclude that the ROIs can be extracted in the XML domain and that the ROIs in the adapted bitstream are still intact without quality degradation. Furthermore, the traditional drifting problem caused by the ROI extraction can be neglected. Finally, we show that the adaptation process in the XML domain can be executed in real time.

Fully Format Agnostic Media Resource Adaptation using an Abstract Model for Scalable Bitstreams

Due to the increasing heterogeneity in network and terminal capabilities, the delivery of multimedia content has become an important issue today. In order to avoid offering multiple versions of the same media resource, a transparent approach under the form of scalable coding is needed for multimedia delivery systems. This paper proposes a fully format agnostic adaptation engine for scalable bitstreams by relying on an abstract model for these bitstreams. The adaptation technique is implemented by making use of the MPEG-21 Digital Item Adaptation specification. The approach is validated for five different scalable coding formats. Experimental results show that our fully format agnostic adaptation node customizes scalable bitstreams in real time (at a speed of more than 100 Mbit/s).