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 XUL-driven video adaptation framework. The performance of a BSD transformation engine is very important in such an 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

XML-driven exploitation of combined scalability in scalable H.264/AVC bitstreams

The heterogeneity in the contemporary multimedia environments requires a format-agnostic adaptation framework for the consumption of digital video content. Scalable bitstreams can be used in order to satisfy as many circumstances as possible. In this paper, the scalable extension on the H.264/AVC specification is used to obtain the parent bitstreams. The adaptation along the combined scalability axis of the bitstreams is done in a format-independent manner. Therefore, an abstraction layer of the bitstream is needed. In this paper, XML descriptions are used representing the high-level structure of the bitstreams by relying on the MPEG-21 Bitstream Syntax Description Language standard. The exploitation of the combined scalability is executed in the XML domain by implementing the adaptation process in a Streaming Transformation for XML (STX) stylesheet. The algorithm used in the transformation of the XML description is discussed in detail in this paper. From the performance measurements, one can conclude that the STX transformation in the XML domain and the generation of the corresponding adapted bitstream can be realized in real time

MPEG-21 session mobility for heterogeneous devices

Nowadays, multimedia is becoming an important part of our live. Every day, the number of people that are having multimedia experiences is augmenting. To allow this growth in multimedia experiences, a new set of devices has been developed. Each of those devices has different terminal and network capabilities, or even different functionalities. As a result of this growing variety of devices, more and more people tend to use several devices for multimedia consumption. Having a wide set of devices for multimedia experiences, results in a demand for seamless switching between devices, better known as session mobility. In this paper, we discuss how session mobility can be realized between heterogeneous devices using MPEG-21 technology. First, we give an overview of the difficulties that occur when doing session mobility between heterogeneous devices. After this problem statement, we give a detailed discussion on how to overcome those difficulties by using MPEG-21. Throughout this paper, we will demonstrate how different parts of MPEG-21 can be integrated into a complete MPEG-21 compliant multimedia framework that facilitates session mobility between heterogeneous devices

A real-time XML-based adaptation system for scalable video formats

Scalable bitstreams are used today to contribute to the Universal Multimedia Access (UMA) philosophy, i.e., accessing multimedia anywhere, at anytime, and on any device. Bitstream structure description languages provide means to adapt scalable bitstreams in order to extract a lower quality version. This paper introduces a real-time XML-based framework for content adaptation by relying on BFlavor, a combination of two existing bitstream structure description languages (i.e., the MPEG-21 Bitstream Syntax Description Language (BSDL) and the Formal Language for Audio-Visual Representation extended with XML features (XFlavor)). In order to use BFlavor with state-of-the-art media formats, we have added support for transparent retrieval of context information and support for emulation prevention bytes. These extensions are validated by building a BFlavor code for bitstreams compliant with the scalable extension of the H.264/AVC specification. Performance measurements show that such a bitstream (containing a bitrate of 17 MBit/s) can be adapted in real-time by a BFlavor-based adaptation framework (with a speed of 27 MBit/s)