Jack Jansen

CMIFed: a presentation environment for portable hypermedia documents

This paper discusses the architecture and implementation of CMIFed, an editing and presentation environment for hypermedia documents. Typically such documents contain a mixture of text, images, audio, and video (and possibly other media), augmented with user interaction. CMIFed allows the author flexibility in specifying what is presented when, using multiple simultaneous output channels. Unlike systems that use a timeline or scripting metaphor to control the presentation, in CMIFed the user manipulates a collection of events and timing constraints among those events. Common timing requirements can be specified by grouping events together in a tree whose nodes indicate sequential and parallel composition. More general timing constraints between events can be added in the form of synchronization arcs. User interaction is supported in the form of hyperlinks. We place CMIFed in the context of the CMIF model for hypermedia documents, which formalizes the properties of hypermedia presentations in a platform-independent manner. CR Subject Classification (1991): H.5.1, H.5.2, I.7.2, I.3.6, I.3.4, D.4.1, D.4.4, D.4.7.

Replication techniques for speeding up parallel applications on distributed systems

Most methods for programming loosely coupled systems are based on message‐passing. Recently, however, methods have emerged based on ‘virtually’ sharing data. These methods simplify distributed programming, but are hard to implement efficiently, as loosely coupled systems do not contain physical shared memory. We introduce a new model, the shared data‐object model, that eases the implementation of parallel applications on loosely coupled systems, but can still be implemented efficiently. In our model, shared data are encapsulated in passive data‐objects, which are variables of user‐defined abstract data types. To speed up access to shared data, data‐objects are replicated. This ability to replicate objects is a significant difference with other object‐based models (e.g. Emerald and Amber). Also, by replicating logical objects rather than physical pages, our model has many advantages over shared virtual memory systems. This paper discusses the design choices involved in replicating objects and their effect on performance. Important issues are: how to maintain consistency among different copies of an object; how to implement changes to objects; which strategy for object replication to use. We have implemented several options to determine which ones are the most efficient. Copyright

Enhancing social sharing of videos: fragment, annotate, enrich, and share

Media consumption is an inherently social activity, serving to communicate ideas and emotions across both small- and large-scale communities. The migration of the media experience to personal computers retains social viewing, but typically only via a non-social, strictly personal interface. This paper presents an architecture and implementation for media content selection, content (re)organization, and content sharing within a user community that is heterogeneous in terms of both participants and devices. In addition, our application allows the user to enrich the content as a differentiated personalization activity targeted to his/her peer-group. We describe the goals, architecture and implementation of our system in this paper. In order to validate our results, we also present results from two user studies involving disjoint sets of test participants.

Fragment, tag, enrich, and send: Enhancing social sharing of video

The migration of media consumption to personal computers retains distributed social viewing, but only via nonsocial, strictly personal interfaces. This article presents an architecture, and implementation for media sharing that allows for enhanced social interactions among users. Using a mixed-device model, our work allows targeted, personalized enrichment of content. All recipients see common content, while differentiated content is delivered to individuals via their personal secondary screens. We describe the goals, architecture, and implementation of our system in this article. In order to validate our results, we also present results from two user studies involving disjoint sets of test participants.

Ambulant: a fast, multi-platform open source SMIL player

This paper provides an overview of the Ambulant Open SMIL player. Unlike other SMIL implementations, the Ambulant Player is a reconfigureable SMIL engine that can be customized for use as an experimental media player core. The Ambulant Player is a reference SMIL engine that can be integrated in a wide variety of media player projects. This paper starts with an overview of our motivations for creating a new SMIL engine, then discusses the architecture of the Ambulant Core (including the scalability and custom integration features of the player). We close with a discussion of our implementation experiences with Ambulant instances for Windows, Mac and Linux versions for desktop and PDA devices.

An affordable optical head tracking system for desktop VR/AR systems

We present an affordable optical head tracking system for desktop-like VR/AR environments. The generic and specific head tracking requirements for these type of environments are de ned, as well as the relaxations such environments put on head tracking systems. The presented head tracker is based on two low-cost, commodity FireWire cameras that track a simple 3D dot pattern. It is shown that the tracker provides high accuracy, an update rate of 30 updates per second, a low computational load, and a moderate delay of 66 ms. It is competitive to commercially available, moderate-cost head tracking systems yet for substantially lower costs.

Enabling Composition-Based Video-Conferencing for the Home

This paper describes a videoconferencing system that meets performance constraints and functional requirements for use in consumer homes. Our system improves existing home technologies (such as video chat) by providing high-quality audiovisual communication, efficient encoding mechanisms, and low end-to-end delay. Moreover, the system includes a control interface that is capable of dynamically manipulating and compositing audiovisual content streams. This innovative architectural component is required for a domestic setting, where the television acts as the main screen and multiple people gather around it. Apart from the requirements and architecture, this paper analyses the performance of our system. The results validate our architectural decisions and provide a valuable input for further research in domestic videoconferencing.

Leveraging user impact: an architecture for secondary screens usage in interactive television

This paper reports on an architecture, and a working implementation, for using secondary screens in the interactive television environment. While there are specific genres and programs that immerse the viewer into the television experience, there are situations in which people perform as well a secondary task, whilst watching. In the living room, people surf the web, use email, and chat using one or many secondary screens. Instead of focusing on unrelated activities to television watching, the architecture presented in this paper aims at related activities, i.e., to leverage the user impact on the content being watched. After a comprehensive literature review and working systems analysis, the requirements for the secondary screen architecture are identified and modelled in the form of a taxonomy. The taxonomy is divided into three high-level categories: control, enrich, and share content. By control we refer to the decision what to consume and where to render it. In addition, the viewer can use the secondary screen for enriching media content and for sharing the enriched material. The architecture is validated based on the taxonomy and by an inspection of the available services. The final intention of our work is to leverage the viewers’ control over the consumed content in our multi-person, multi-device living rooms.

Enabling adaptive time-based web applications with SMIL state

In this paper we examine adaptive time-based web applications (or presentations). These are interactive presentations where time dictates the major structure, and that require interactivity and other dynamic adaptation. We investigate the current technologies available to create such presentations and their shortcomings, and suggest a mechanism for addressing these shortcomings. This mechanism, SMIL State, can be used to add user-defined state to declarative time-based languages such as SMIL or SVG animation, thereby enabling the author to create control flows that are difficult to realize within the temporal containment model of the host languages. In addition, SMIL State can be used as a bridging mechanism between languages, enabling easy integration of external components into the web application.

SMIL State: an architecture and implementation for adaptive time-based web applications

In this paper we examine adaptive time-based web applications (or presentations). These are interactive presentations where time dictates which parts of the application are presented (providing the major structuring paradigm), and that require interactivity and other dynamic adaptation. We investigate the current technologies available to create such presentations and their shortcomings, and suggest a mechanism for addressing these shortcomings. This mechanism, SMIL State, can be used to add user-defined state to declarative time-based languages such as SMIL or SVG animation, thereby enabling the author to create control flows that are difficult to realize within the temporal containment model of the host languages. In addition, SMIL State can be used as a bridging mechanism between languages, enabling easy integration of external components into the web application. Finally, SMIL State enables richer expressions for content control. This paper defines SMIL State in terms of an introductory example, followed by a detailed specification of the State model. Next, the implementation of this model is discussed. We conclude with a set of potential use cases, including dynamic content adaptation and delayed insertion of custom content such as advertisements.