Representing digital assets usingMPEG-21 Digital Item Declaration

Various XML-based approaches aimed at representing compound digital assets have emerged over the last several years. Approaches that are of specific relevance to the digital library community include the Metadata Encoding and Transmission Standard (METS), the IMS Content Packaging XML Binding, and the XML Formatted Data Units (XFDU) developed by CCSDS Panel 2. The MPEG-21 Digital Item Declaration (MPEG-21 DID) is another standard specifying the representation of digital assets in XML that, so far, has received little attention in the digital library community. This article gives a brief insight into the MPEG-21 standardization effort, highlights the major characteristics of the MPEG-21 DID Abstract Model, and describes the MPEG-21 Digital Item Declaration Language (MPEG-21 DIDL), an XML syntax for the representation of digital assets based on the MPEG-21 DID Abstract Model. Also, it briefly demonstrates the potential relevance of MPEG-21 DID to the digital library community by describing its use in the aDORe repository environment at the Research Library of the Los Alamos National Laboratory (LANL) for the representation of digital assets.     

一种MPEG-21实验床的研究及测试

文章在Linux操作系统下搭建了一种MPEG-21实验床,该实验床为MPEG-21的各项应用研究提供了一个很好的测试环境。在实验床的真实网络场景下,针对网络性能对视频质量的影响进行了分析。该分析结果为今后改进视频传输的性能提供了有益的启示。     

MPEG-21 digital item declaration and Identification-principles and compression

At the core of the MPEG-21 Multimedia Framework is the concept of the Digital Item, a virtual container for a hierarchical structure of metadata and resources. This paper considers the Digital Item Declaration Language (DIDL), gives examples of its usage, and discusses how it is used to integrate other parts of MPEG-21. The paper then discusses how Digital Item Identification integrates with the DIDL to allow MPEG-21 to utilize standard identifiers from many application spaces. Finally, an alternative, compressed form of the XML Digital Item Declaration is described. This uses schema-based compression to significantly reduce the size of these XML documents.     

Optical flow approximation based motion object extraction for MPEG-2 video stream

This paper presents a compressed-domain motion object extraction algorithm based on optical flow approximation for MPEG-2 video stream. The discrete cosine transform (DCT) coefficients of P and B frames are estimated to reconstruct DC + 2AC image using their motion vectors and the DCT coefficients in I frames, which can be directly extracted from MPEG-2 compressed domain. Initial optical flow is estimated with Black’s optical flow estimation framework, in which DC image is substituted by DC + 2AC image to provide more intensity information. A high confidence measure is exploited to generate dense and accurate motion vector field by removing noisy and false motion vectors. Global motion estimation and iterative rejection are further utilized to separate foreground and background motion vectors. Region growing with automatic seed selection is performed to extract accurate object boundary by motion consistency model. The object boundary is further refined by partially decoding the boundary blocks to improve the accuracy. Experimental results on several test sequences demonstrate that the proposed approach can achieve compressed-domain video object extraction for MPEG-2 video stream in CIF format with real-time performance.     

A first approach to speeding-up the inter mode selection in MPEG-2/H.264 transcoders using machine learning

The H.264 standard achieves much higher coding efficiency than the MPEG-2 standard, due to its improved inter and intra prediction modes which come with a cost of higher computation complexity. Transcoding MPEG-2 video to H.264 is important to enable gradual migration to H.264. However, given the significant differences between the MPEG-2 and the H.264 coding algorithms, transcoding is much more complex and new approaches to transcoding are necessary. In this paper, we introduce and evaluate a low complexity macroblock partition mode decision algorithm, to be used as part of a high-efficient inter-frame prediction in MPEG-2 to H.264 transcoder. The proposed tools are used to compute an optimal MB coding mode decision with significantly reduced computational complexity. Specifically, we achieve the computational savings by using the following MB information coming from MPEG-2: the MB coding modes, the coded block pattern (CBPC) in MPEG-2, and the mean and variance of the 16 4 × 4 sub blocks of the MPEG-2 residual MBs. We use data mining algorithms to develop a decision tree for H.264 coding mode decisions. The decision trees are built using RD optimized mode decisions and result in highly efficient mode decisions, with significantly reduced computational complexity. The proposed transcoder is 35% faster than the RD optimized H.264 reference transcoder without a significant PSNR degradation (0.05 dB on average). The proposed transcoder performs over 0.4 dB better on average than the SAE cost based H.264 transcoding.

Digital item adaptation: overview of standardization and research activities

MPEG-21 Digital Item Adaptation (DIA) has recently been finalized as part of the MPEG-21 Multimedia Framework. DIA specifies metadata for assisting the adaptation of Digital Items according to constraints on the storage, transmission and consumption, thereby enabling various types of quality of service management. This paper provides an overview of DIA, describes its use in multimedia applications, and reports on some of the ongoing activities in MPEG on extending DIA for use in rights governed environments.     

From MPEG-7 user interaction tools to hanging basket models: bridging the gap

The content–user gap is the difference between the limited range of content-relevant preferences that may be expressed using the MPEG-7 user interaction tools and the much wider range of metadata that may be represented using the MPEG-7 content tools. One approach for closing this gap is to make the user and content metadata isomorphic by using the existing MPEG-7 content tools to represent user (as well as content) metadata (Agius and Angelides 2006, 2007). Subsequently, user preferences may be specified for all content, without omission. Since there is a wealth of user preference and history metadata within the MPEG-7 user interaction tools that can usefully complement these specific content preferences, in this paper we develop a method by which all user and content metadata may be bridged.

A high-brightness diffractive stereoscopic display technology

In this research, the diffractive blazed grating was proposed to produce the stereoscopic effects that were traditionally generated by barrier grating through parallax barrier method. Three wavelengths, 596 nm, 554 nm and 450 nm, were chosen as the main light waves for three sub-pixels, RGB. Because the diffractive optical element was directly attached to the color filter of a MPEG-4 player (Motion Picture Experts Group Four Player, MPEG-4 player) panel, the stereoscopic image remained high brightness. Since lithography would be the most possible manufacturing method, multilevel approximation was to proceeded during simulation. From the simulated results of optical simulation software, LightTools, the RGB lights moved parallelly and consequently avoiding cross-talk.     

Visual content adaptation according to user perception characteristics

Adapting multimedia content to users' preferences and perceptual characteristics is a key direction for enabling personalized multimedia services. In this paper, we address the problem of tailoring visual content within the MPEG-21 Digital Item Adaptation (DIA) framework to meet users' visual perception characteristics. In particular, we present methods for adapting visual content to accommodate color vision deficiency and low-vision capabilities. In addition, we present methods for adapting visual content according to user preferences for color temperature. Finally, we report on experiments that adapt visual content within the MPEG-21 DIA framework.     

DCAF: An MPEG-21 Dynamic Content Adaptation Framework

Universal Multimedia Access aims at providing a gratifying end user-experience by either adapting the content, be it static or dynamic, to suit the usage environment or adapting the usage environment, be it client- or server-centric, to suit content. This paper presents our MPEG-21 Dynamic Content Adaptation Framework, acronym DCAF, which uses a fusion of Genetic Algorithms and Strength Pareto Optimality to adapt content in order to suit the usage environment.

MPEG的新发展——多媒体框架标准MPEG-21

标准化是产业化活动成功的前提，视、音频编码的各种国际标准的制定集中地反映了视、音频编码技术发展的水平．目前，图象压缩方面的标准主要有MPEG系列(MPEG-1，MPEG-2，MPEG-4，MPEG-7和MPEG-21标准)，以及H．26X系列(H．261，H．263标准)和静止图象压缩标准JPEG．为了使人们对图象压缩标准有所了解，以进一步推动图象压缩方面的研究，首先对MPEG系列的各种已有标准及其应用进行了概述，然后着重讨论了MPEG中的新面孔——正在开发的MPEG-21标准，并就其目标、用户需求、技术要素、关键任务、应用领域以及工作计划做了较详细的描述．     

基于感知运动能量模型的MPEG-21数字项适配

最新的MPEG-21标准定义了一个统一的多媒体框架,其目标是使多媒体资源能在异构网络和终端上进行透明传输和得到充分利用。多媒体适配(Multimedia Adaptation)技术作为实现上述目标的关键技术得到了越来越多的研究。本文将感知运动能量模型与MPEG-21数字项适配框架相结合,研究和实现了基于感知运动能量的H．264／AVC视频丢帧适配技术。本文的研完工作有两个方面的优点：一方面,感知运动能量模型的使用将丢帧适配引起的运动抖动减至最小,保证了较高的用户视觉上的主观感知质量;另一方面,数据处理能力和资源受限的适配节点不需了解具体的H．264／AVC编码语法结构和编解码算法,就能方便地执行丢帧操作,实现了独立于媒体编码格式的视频适配机制,提高了多媒体适配系统的灵活性和可扩展性。     

Packaging models for the storage and distribution of complex digital objectsin archival information systems: a review of MPEG-21 DID principles

In recent years, the number of organizations making digital information available has increased dramatically. This evolution has encouraged the development of various approaches to represent complex digital objects. Approaches that are of specific relevance to the digital library and archiving community include the Metadata Encoding and Transmission Standard (METS), the Content Packaging XML Binding of the Instructional Management System (IMS) project, and the Sharable Content Object Reference Model (SCORM). The MPEG-21 Digital Item Declaration MPEG-21 DID) is yet another packaging approach that, so far, has received little attention in the digital library community. The primary goal of this article is to offer a method to compare these packaging approaches in the context of the needs of the digital library community and the rising digital preservation programs. The contribution of this paper is the definition of an integrated reference framework, based on both the ISO OAIS Reference Model and a set of additional significant properties that affect the quality, usability, encoding, and behavior of complex digital objects. This article also gives a brief insight into MPEG-21 DID and examines its potential relevance by showing the results obtained from applying the proposed reference framework. Published online: 8 April 2005     

Device-based decision-making for adaptation of three-dimensional content

The goal of this research was the creation of an adaptation mechanism for the delivery of three-dimensional content. The adaptation of content, for various network and terminal capabilities – as well as for different user preferences, is a key feature that needs to be investigated. Current state-of-the art research of the adaptation shows promising results for specific tasks and limited types of content, but is still not well-suited for massive heterogeneous environments. In this research, we present a method for transmitting adapted three-dimensional content to multiple target devices. This paper presents some theoretical and practical methods for adapting three-dimensional content, which includes shapes and animation. We also discuss practical details of the integration of our methods into MPEG-21 and MPEG-4 architectures.     

The MPEG-21 rights expression language and rights data dictionary

The MPEG-21 Rights Expression Language (REL) is an XML-based language for digital rights management (DRM), providing a universal method for specifying rights and conditions associated with the distribution and use of assets like content, resources and services. Evolved from the eXtensible rights Markup language (XrML), the REL facilitates the creation of an open DRM architecture for managing and protecting these assets. As a general-purpose rights expression language, the REL is agnostic to types of assets, platforms and media, and expressive enough to support applications that can be even beyond DRM, including protecting privacy. It also contains additional capabilities in the areas of extensibility, security, trust management, and life cycle management of rights. This article provides an overview of the REL in terms of its data model, expressiveness, authorization model, structure for extensibility and profiling, and usages in digital media, trust management, and web services. To support the REL and provide extensive semantics for the management of rights, MPEG-21 also defined a Rights Data Dictionary (RDD). Based on original work conducted by , the MPEG-21 RDD specifies a methodology and structure for the RDD dictionary. The specification defines a core set of terms and provides a mechanism for the introduction of further terms through a registration authority. The RDD also supports the mapping of terms from different namespaces.     

A game approach to optimization of bandwidth allocation using MPEG-7 and MPEG-21

Resource allocation aims at optimizing the usage of shared resources and maximizing the end-user experience by determining the optimum sharing of resources and choosing whom to serve, how and when. Approaches addressing this challenge are driven by the requirements of the environment and the characteristics of users. This paper addresses the challenge of optimising resource allocation through the combined application of game theory and normative tools such MPEG-21 and MPEG-7. The resulting game play leads to a forced Nash equilibrium where a change of strategy will not make any player better off.     

Metadata-driven optimal transcoding in a multimedia proxy

An adaptive multimedia proxy is presented which provides (1) caching, (2) filtering, and (3) media gateway functionalities. The proxy can perform media adaptation on its own, either relying on layered coding or using transcoding mainly in the decompressed domain. A cost model is presented which incorporates user requirements, terminal capabilities, and video variations in one formula. Based on this model, the proxy acts as a general broker of different user requirements and of different video variations. This is a first step towards What You Need is What You Get (WYNIWYG) video services, which deliver videos to users in exactly the quality they need and are willing to pay for. The MPEG-7 and MPEG-21 standards enable this in an interoperable way. A detailed evaluation based on a series of simulation runs is provided.