A novel method is presented for inaudibly hiding information in an audio signal by subtly applying time-scale modification to segments of the signal. The sequence, duration, and degree of the time-scale modifications are the parameters which encode information in the altered signal. By comparing the altered signal with a reference copy, compressed and expanded regions can be identified and the hidden data recovered. This approach is novel and has several advantages over other methods: it is theoretically noiseless, it introduces no spectral distortion, and it is robust to all known methods of reproduction, compression, and transmission.

We created an improved layout algorithm for automatically generating visual video summaries reminiscent of comic book pages. The summaries are comprised of images from the video that are sized according to their importance. The algorithm performs a global optimization with respect to a layout cost function that encompasses features such as the number of resized images and the amount of whitespace in the presentation. The algorithm creates summaries that: always fit exactly into the requested area, are varied by containing few rows with images of the same size, and have little whitespace at the end of the last row. The layout algorithm is fast enough to allow the interactive resizing of the summaries and the subsequent generation of a new layout.

We created an alternative approach to existing video summaries that gives viewers control over the summaries by selecting hyperlinks to other video with additional information. We structure such summaries as "detail-on-demand" video, a subset of general hypervideo in which at most one link to another video sequence is available at any given time. Our editor for such video, Hyper-Hitchcock, provides a workspace in which an author can select and arrange video clips, generate composites from clips and from other composites, and place links between composites. To simplify dealing with a large number of clips, Hyper-Hitchcock generates iconic representations for composites that can be used to manipulate the composite as a whole. In addition to providing an authoring environment, Hyper-Hitchcock can automatically generate multi-level hypervideo summaries for immediate use or as the starting point for author modification.

This paper presents an information-driven audiovisual signal acquisition approach. This approach has several advantages: users are encouraged to assist in signal acquisition; available sensors are managed based on both signal characteristics and users' suggestions. The problem formulation is consistent with many well-known empirical approaches widely used in previous systems and may provide analytical explanations to these approaches. We demonstrate the use of this approach to pan/tilt/zoom (PTZ) camera management with field data.

A basic objective of ubiquitous computing research is ubiquitous information: the ability to utilize any content or service, using devices that are always at hand, over networks that don't tie us down. Although much progress has been made, the ideal remains elusive. This paper reflects on the interrelations among three dimensions of ubiquitous information: content, devices, and networks. We use our understanding of these dimensions to motivate our own attempt to create a ubiquitous information system by combining unlimited World Wide Web content with mobile phones and mobile phone networks. We briefly describe a middleware proxy system we developed to increase the usefulness of very small devices as Internet terminals. We conclude with a post-mortem analysis highlighting lessons learned for others interested in information systems for very small devices.

Everywhere we go, we are surrounded by shared devices: TVs, stereos, and appliances in the home; copiers, fax machines, and projectors in the office; phones and vending machines in public. Because these devices don't know who we are, they provide the same user interface and functionality to everyone. This paper describes a system for personalizing workplace document devices- projectors, public displays, and multi-function copiers-that has been in use for over two years in our organization. We compare user interfaces that are embedded (i.e., integrated or co-located with the shared device) versus portable (i.e., accessible via portable devices such as mobile phones or PDAs). We summarize lessons learned for others designing interfaces for shared ubiquitous devices.

Purveyors of knowledge management software have a disconcerting tendency to promote the myth that all problems may be solved by more powerful tools for the exchange of information in the workplace. This fallacy is based on the faulty assumption that knowledge management is about the management of knowledge (as if knowledge were a commodity that could be managed), as opposed to the management of people whose work depends critically on what they know. The origins of knowledge management are far more firmly rooted in the psychological legacy of organizational communication than they are in the technological legacy of information management systems. However, even organizational communication is an inadequate foundation, since various schools of thought in social theory, particularly the structuration theory of Anthony Giddens, inform us that interaction (in the workplace or in any other social setting) is not strictly limited to communication. Knowledge management thus requires moving beyond simplistic models of information exchange to more challenging problems of leveraging social interaction to the advantage of the enterprise. This paper focuses on the claim of structuration theory that the dimension of communication should be supplemented with additional dimensions of power and sanction. This perspective is then examined in light of a case study of crisis management practices, and the case study provides a basis for addressing implications for technological support.

This is a volume, edited by Ye and Churchill. The chapters detail the design of agent-baed technologies in service of collaborative and cooperative work practices.

In this paper we describe AttrActive Windows, a novel interface for presenting live, interactive, multimedia content on a network of public, digital, bulletin boards. Implementing a paper flyer metaphor, AttrActive Windows are paper-like in appearance and are attached to a virtual corkboard by virtual pushpins. Windows can therefore appear in different orientations, creating an attractive, informal look. Attractive Windows can also have autonomous behaviors that are consistent with the corkboard metaphor, like fluttering in the wind. We describe the AttrActive Windows prototype, and offer the results of an initial evaluative user study.

Shared freeform input is a technique for facilitating note taking across devices during a meeting. Laptop users enter text with a keyboard, whereas PDA and Tablet PC users input freeform ink with their stylus. Users can quickly reuse text and freeform ink already entered by others. We show how a new technique, freeform pasting, allowed us to deal with a variety of design issues such as quick and informal ink sharing, screen real estate, privacy and mixing ink-based and textual material.

This chapter is an introduction to an edited volume on Agnet supported cooperative work.

An introduction to a special issue on mediated communication.

We present a framework for analyzing the structure of digital media streams. Though our methods work for video,text,and audio,we concentrate on detecting the structure of digital music files. In the first step,spectral data is used to construct a similarity matrix calculated from inter-frame spectral similarity. The digital audio can be robustly segmented by correlating a ernel along the diagonal of the similarity matrix. Once segmented, spectral statistics of each segment are computed.In the second step,segments are clustered based on the self- similarity of their statistics. This reveals the structure of the digital music in a set of segment boundaries and labels.Finally,the music can be summarized by selecting clusters with repeated segments throughout the piece. The summaries can be customized for various applications based on the structure of the original music.

We introduce the AttrActive Windows user interface, a novel approach for presenting interactive content on large screen, interactive, digital, bulletin boards. Moving away from the desktop metaphor, AttrActive Windows are dynamic, non-uniform windows that can appear in different orientations and have autonomous behaviours to attract passers-by and invite interactions.

We present a novel approach to automatically ex-tracting summary excerpts from audio and video. Our approach is to maximize the average similarity between the excerpt and the source. We first calculate a similarity matrix by comparing each pair of time samples using a quantitative similarity measure. To determine the segment with highest average similarity, we maximize the summation of the self-similarity matrix over the support of the segment. To select multiple excerpts while avoiding redundancy, we compute the non-negative matrix factorization (NMF) of the similarity matrix into its essential structural components. We then build a summary comprised of excerpts from the main components, selecting the excerpts for maximum average similarity within each component. Variations integrating segmentation and other information are also discussed, and experimental results are presented.

Hitchcock is a semi-automatic video editing system. This video shows users collaboratively authoring a home video.

We present methods for automatic and semi-automatic creation of music videos, given an arbitrary audio soundtrack and source video. Significant audio changes are automatically detected; similarly, the source video is automatically segmented and analyzed for suitability based on camera motion and exposure. Video with excessive camera motion or poor contrast is penalized with a high unsuitability score, and is more likely to be discarded in the final edit. High quality video clips are then automatically selected and aligned in time with significant audio changes. Video clips are adjusted to match the audio segments by selecting the most suitable region of the desired length. Besides a fully automated solution, our system can also start with clips manually selected and ordered using a graphical interface. The video is then created by truncating the selected clips (preserving the high quality portions) to produce a video digest that is synchronized with the soundtrack music, thus enhancing the impact of both.

FlySPEC is a video camera system designed for real-time remote operation. A hybrid design combines the high resolution possible using an optomechanical video camera, with the wide field of view always available from a panoramic camera. The control system integrates requests from multiple users with the result that each controls a virtual camera. The control system seamlessly integrates manual and fully automatic control. It supports a range of options from untended automatic to full manual control, and the system can learn control strategies from user requests. Additionally, the panoramic view is always available for an intuitive interface, and objects are never out of view regardless of the zoom factor. We present the system architecture, an information-theoretic approach to combining panoramic and zoomed images to optimally satisfy user requests, and experimental results that show the FlySPEC system significantly assists users in a remote inspection tasks.

Technology can play an important role in enabling people to interact with each other. The Web is one such technology with the affordances for sharing information and for connecting people to people. In this paper, we describe the design of two social interaction Web sites for two different social groups. We review several related efforts to provide principles for creating social interaction environments and describe the specific principles that guided our design. To examine the effectiveness of the two sites, we analyze the usage data. Finally, we discuss approaches for encouraging participation and lessons learned.

Freeform digital ink annotation allows readers to interact with documents in an intuitive and familiar manner. Such marks are easy to manage on static documents, and provide a familiar annotation experience. In this paper, we describe an implementation of a freeform annotation system that accommodates dynamic document layout. The algorithm preserves the correct position of annotations when documents are viewed with different fonts or font sizes, with different aspect ratios, or on different devices. We explore a range of heuristics and algorithms required to handle common types of annotation, and conclude with a discussion of possible extensions to handle special kinds of annotations and changes to documents.

This work presents constructs called interactive space-time maps along with an application called the SpaceTime Browser for visualizing and retrieving documents. A 3D visualization with 2D planar maps and a time line is employed. Users can select regions on the maps and choose precise time intervals by sliding the maps along the telescopic time line. Regions are highlighted to indicate the presence of documents with matching space-time attributes, and documents are retrieved and displayed in an adjoining workspace. We provide two examples: (1) organizing travel photos, (2) managing documents created by room location-aware devices in a building.

This paper describes how the changing information about an individual's location, environment, and social situation can be used to initiate and facilitate people's interactions with one another, individually and in groups. Context-aware communication is contrasted with other forms of context-aware computing and we characterize applications in terms of design decisions along two dimensions: the extent of autonomy in context sensing and the extent of autonomy in communication action. A number of context-aware communication applications from the research literature are presented in five application categories. Finally, a number of issues related to the design of context-aware communication applications are presented.

Squeezing desktop Web content into smart phones and text pagers is more practical with separate interfaces for navigation and content manipulation. m-Links, a middleware proxy system, supports this dual-mode browsing, offering phonetop users an extendable set of actions.

We present methods for automatically producing summary excerpts or thumbnails of music. To find the most representative excerpt, we maximize the average segment similarity to the entire work. After window-based audio parameterization, a quantitative similarity measure is calculated between every pair of windows, and the results are embedded in a 2-D similarity matrix. Summing the similarity matrix over the support of a segment results in a measure of how similar that segment is to the whole. This measure is maximized to find the segment that best represents the entire work. We discuss variations on the method, and present experimental results for orchestral music, popular songs, and jazz. These results demonstrate that the method finds significantly representative excerpts, using very few assumptions about the source audio.