Showing papers by "Christian Timmerer published in 2007"

Towards MPEG-21-Based Cross-Layer Multimedia Content Adaptation

Abstract: Cross-layer designs are becoming more and more attractive within the multimedia community since multiple-play services pave their way towards consumer markets enabling mobility in various aspects However, cross-layer designs so far have mainly focused on performance issues and do not provide much support in terms of interoperability which is a requirement for services envisaged as part of the Fixed-Mobile Service Convergence (FMSC) initiative This paper presents a first attempt towards increasing the interoperability of cross-layer designs by adopting an open standard - MPEG-21 Digital Item Adaptation - for describing the functional dependencies across network layers In this paper a three-step approach for multimedia content adaptation is presented that introduces an MPEG-21-based cross- layer architecture

Efficient MPEG-21-based Adaptation Decision-Taking for Scalable Multimedia Content

Abstract: The MPEG-21 standard defines a framework for the interoperable delivery and consumption of multimedia content. Within this framework the adaptation of content plays a vital role in order to support a variety of terminals and to overcome the limitations of the heterogeneous access networks. In most cases the multimedia content can be adapted by applying different adaptation operations that result in certain characteristics of the content. Therefore, an instance within the framework has to decide which adaptation operations have to be performed to achieve a satisfactory result. This process is known as adaptation decision-taking and makes extensive use of metadata describing the possible adaptation operations, the usage environment of the consumer, and constraints concerning the adaptation. Based on this metadata a mathematical optimization problem can be formulated and its solution yields the optimal parameters for the adaptation operations. However, the metadata is represented in XML resulting in a verbose and inefficient encoding. In this paper, an architecture for an Adaptation Decision-Taking Engine (ADTE) is introduced. The ADTE operates both on XML metadata and on metadata encoded with MPEG's Binary Format for Metadata (BiM) enabling an efficient metadata processing by separating the problem extraction from the actual optimization step. Furthermore, several optimization algorithms which are suitable for scalable multimedia formats are reviewed and extended where it was appropriate.,

Processing and Delivery of Multimedia Metadata for Multimedia Content Streaming.

Abstract: Today’s increasing variety of media data results in a great diversity of XMLbased metadata, which describes the media data on semantic or syntactic levels, in order to make it more accessible to the user This metadata can be of considerable size, which leads to problems in streaming scenarios Other than media data, XML metadata has no concept of “samples”, thus inhibiting streamed (and timed) processing, which is natural for media data In order to address the challenges and requirements resulting from this situation, the concept of streaming instructions is introduced In particular, streaming instructions address the problem of fragmenting metadata, associating media segments and metadata fragments, and streaming and processing them in a synchronized manner This is achieved by enriching the metadata with additional attributes to describe media and XML properties Alternatively, a style sheet approach provides the opportunity to dynamically set such streaming properties without actually modifying the XML description 1 Motivation and Scope The role of XML-based metadata for describing distributed, advanced multimedia content gains more and more popularity in order to increase the access of such contents from anywhere and anytime In the past, two main categories for this kind of metadata have become apparent [Fo06] The first category of metadata aims to describe the semantics of the content such as keywords, violence ratings, or classifications Metadata standards supporting this category are MPEG-7, TV Anytime, and SMPTE among others [AKS03] The second 1 Work partly supported by the IST European projects DANAE (IST-1-507113) and ENTHRONE (n° 038463) category of metadata does not describe the semantics, but rather the syntax and structure of the multimedia content This category spans a wide range of research activities enabling codec-agnostic adaptation engines for scalable contents by providing languages for describing the bitstream syntax Examples for such languages are the Bitstream Syntax Description Language (BSDL) as specified in MPEG-21 DIA [Ve04], BFlavor [De06], and XFlavor [HE02] Note that MPEG-7 also provides means for describing syntactical aspects of multimedia bitstreams [BS06] Both categories of metadata (semantic and syntactic descriptions) have in common that they are desired to become more and more detailed, as this increases the accessibility of the media content They often describe the content per segment or even per access unit (AU), which are the fundamental units for transport of media streams and are defined as the smallest data entity which is atomic in time, ie, to which a single decoding time can be attached For example, a single violence rating for the whole movie might exclude many potential consumers if it contains only one or two extremely violent scenes However, if the violence rating is provided per scene, for instance, the problematic scenes could simply be skipped for viewers who do not wish to see them Similarly, if a scalable multimedia content only describes the temporal enhancement layers, terminals requiring spatial adaptation (eg, a mobile device) are excluded Again, more descriptive metadata (ie, describing spatial, temporal, and fine-grained scalability) would increase the accessibility of the content As a consequence, this metadata is often of a considerable size, which – even when applying compression – is problematic in streaming scenarios That is, transferring entire metadata files – if possible at all – before the actual transmission of the media data, could lead to a significant startup delay Additionally, there is no information on how this metadata is synchronized with the corresponding media, which is necessary for streamed (ie, piecewise) processing thereof The concept of piece-wise (and timed) processing is natural for media data For example, a video consists of a series of independent pictures which are typically taken by a camera These independent pictures are then encoded, typically exploiting the redundancies between these pictures The resulting AUs can depend on each other (eg, in the case of bidirectional encoded pictures) but are still separate packets of data Although the characteristics of content-related metadata are very similar to those of timed multimedia content, no concept of “samples” exists for this metadata today In this paper we introduce the concept of “samples” for metadata by employing streaming instructions for both XML metadata and media data The XML streaming instructions specify the fragmentation of the content-related metadata into meaningful fragments and their timing These fragments are referred to as process units (PUs), which introduce the “samples” concept – known from audio-visual content – to content-related metadata The media streaming instructions are used to locate AUs in the bitstream and to time them properly Both types of streaming instructions enable time-synchronized, piece-wise (ie, streamed) processing and delivery of media data and its related metadata Furthermore, the fragmentation mechanism helps to overcome the startup delay introduced by the size of the metadata Another, less obvious, benefit is described in an application scenario (see Section 5) where the streaming instructions enable to extend an existing static media adaptation approach to dynamic and distributed use cases Section 2 summarizes the requirements for the streaming instructions Related work is discussed in Section 3 Section 4 describes the streaming instructions in detail An application scenario, which illustrates the benefits of the streaming instructions, is presented in Section 5 Section 6 provides a performance evaluation of the streaming instructions and of an adaptation server which facilitates the streaming instructions to enable dynamic and distributed adaptation Section 7 concludes this paper and points out possible future work items

Design and Evaluation of a Metadata-Driven Adaptation Node

Abstract: MPEG-21 digital item adaptation (DIA) allows for a media codec agnostic multimedia adaptation approach which enables the implementation of generic adaptation engines. However, DIA is optimized for static, server-based adaptation. In this paper we introduce novel mechanisms to extend the DIA approach towards dynamic and distributed scenarios. This facilitates the placement of generic adaptation nodes which perform media codec agnostic and dynamic adaptation anywhere along the content delivery path. To validate our work we implemented such an adaptation node and evaluate its performance.