W. De Neve

Flexible macroblock ordering in H.264/AVC

Abstract H.264/AVC is a new standard for digital video compression jointly developed by ITU-T’s Video Coding Experts Group (VCEG) and ISO/IEC’s Moving Picture Experts Group (MPEG). Besides the numerous tools for efficient video coding, the H.264/AVC specification defines some new error resilience tools. One of them is flexible macroblock ordering (FMO) which is the main focus of this paper. An in-depth overview is given of the internals of FMO. Experiments are presented that demonstrate the benefits of FMO as an error resilience tool in case of packet loss over IP networks. The flexibility of FMO comes with a certain overhead or cost. A quantitative assessment of this cost is presented for a number of scenarios. FMO can, besides for pure error resilience, also be used for other purposes. This is also addressed in this paper.

Comparison of conformal radiation therapy techniques within the dynamic radiotherapy project 'Dynarad'

The objective of the dynamic radiotherapy project Dynarad within the European Community has been to compare and grade treatment techniques that are currently applied or being developed at the participating institutions. Cervical cancer was selected as the tumour site on the grounds that the involved organs at risk, mainly the rectum and the bladder, are very close to the tumour and partly located inside the internal target volume. In this work, a solid phantom simulating the pelvic anatomy was used by institutions in Belgium, France, Greece, Holland, Italy, Sweden and the United Kingdom. The results were evaluated using both biological and physical criteria. The main purpose of this parallel evaluation is to test the value of biological and physical evaluations in comparing treatment techniques. It is demonstrated that the biological objective functions allow a much higher conformality and a more clinically relevant scoring of the outcome. Often external beam treatment techniques have to be combined with intracavitary therapy to give clinically acceptable results. However, recent developments can reduce or even eliminate this need by delivering more conformal dose distributions using intensity modulated external dose delivery. In these cases the reliability of the patient set-up procedure becomes critical for the effectiveness of the treatment.

Rate-distortion performance of H.264/AVC compared to state-of-the-art video codecs

In the domain of digital video coding, new technologies and solutions are emerging in a fast pace, targeting the needs of the evolving multimedia landscape. One of the questions that arises is how to assess these different video coding technologies in terms of compression efficiency. In this paper, several compression schemes are compared by means of peak signal-to-noise ratio (PSNR) and just noticeable difference (JND). The codecs examined are XviD 0.9.1 (conform to the MPEG-4 Visual Simple Profile), DivX 5.1 (implementing the MPEG-4 Visual Advanced Simple Profile), Windows Media Video 9, MC-EZBC and H.264/AVC AHM 2.0 (version JM 6.1 of the reference software, extended with rate control). The latter plays a key role in this comparison because the H.264/AVC standard can be considered as the de facto benchmark in the field of digital video coding. The obtained results show that H.264/AVC AHM 2.0 outperforms current proprietary and standards-based implementations in almost all cases. Another observation is that the choice of a particular quality metric can influence general statements about the relation between the different codecs.

Motion Compensation and Reconstruction of H.264/AVC Video Bitstreams using the GPU

Most modern computers are equipped with powerful yet cost-effective graphics processing units (GPUs) to accelerate graphics operations. Although programmable shaders on these GPUs were designed for the creation of 3-D rendering effects, they can also be used as generic processing units for vector data. This paper proposes a hardware Tenderer capable of executing motion compensation, reconstruction, and visualization entirely on the GPU by the use of vertex and pixel shaders. Our measurements show that a speedup of 297% can be achieved by relying on the processing power of the GPU, relative to the CPU. As an example, real-time playback of high-definition video (1080 p) was achieved at 62.0 frames per second, consuming only 68.2% of all CPU cycles on a modern machine.

Generating MPEG-21 BSDL descriptions using context-related attributes

In order to efficiently deal with the heterogeneity in the current and future multimedia ecosystem, it is necessary that content can be adapted in a format-agnostic manner. A first step toward a solution, able to fulfill the just mentioned requirement, is to rely on a scalable video codec and to describe the high-level structure of the resulting bitstreams in such a way that every terminal can understand it, in particular by using XML. This paper describes how such descriptions can be generated by making use of the media format independent BintoBSD tool of the MPEG-21 BSDL standard. However, regarding the current status of BSDL, it is impossible to create a description in real time and to keep the generation speed constant over the complete sequence. In this paper, we describe a number of extensions and algorithmic modifications that make it possible to generate a description of a bitstream in real time and at a constant speed. Our approach results in a significant reduction of the original execution times (up to 99% for the H.264/AVC coding format) and in a constant memory usage.

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

XML-driven Bitrate Adaptation of SVC Bitstreams

Thanks to technological evolutions, the number of devices capable of playing video bitstreams is growing. The heterogeneity in these devices grows in terms of screen resolution, processing power, and available band width. In this paper, we describe an MPEG-21 Bitstream Syntax Description Language- based (BSDL-based) adaptation framework that allows providers to easily adapt scalable bitstreams without having to recode the original bitstream. We describe the steps necessary to adapt the bitstreams through BSDL. The main contribution of this paper is an optimized adaptation framework using a Bitstream Syntax Schema developed to minimize the size of the Bitstream Syntax Descriptions (BSDs). Furthermore, we created a Streaming Transformations for XML Stylesheet (STX-stylesheet) to exploit the advantages of Fine Grain Scalability, this to adapt the bitrate of Scalable Video Coding bitstreams in the most accurate way possible. Our results show that BSDL-based adaptation is able to compete with binary adaptation tools. The target bitrates can be reached within a margin of 2%, which is comparable to the reference software which uses binary adaptation.

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).

XML-based customization along the scalability axes of H.264/AVC scalable video coding

The heterogeneity in the current and future multimedia environment requires an elegant adaptation framework for the production and consumption of different kinds of multimedia content. Such an architecture is preferably based on the usage of scalable bitstreams and a format-agnostic content adaptation engine. To obtain fully embedded scalable bitstreams, the joint scalable video model (JSVM) has been used in this paper. Hereby, JSVM defines a scalable extension on top of the H.264/AVC specification. This extension will make it possible to create bitstreams that are scalable along the temporal, spatial, and SNR axis. On the other hand, bitstream structure descriptions can be used to realize an elegant and format-agnostic adaptation engine. Such descriptions can be created by making use of the MPEG-21 bitstream syntax description language (BSDL) standard. The latter allows to describe the high-level structure of scalable bitstreams in XML. This paper explains how fully scalable bitstreams can be customized by transforming BSDL-based bitstream structure descriptions. From our performance analysis, one can conclude that the transformation of the XML description, as well as the generation of the adapted bitstream, can be done several times faster than real time