The DigitalInteractive VideoExploration andReflection (Diver)system lets userscreate virtualpathways throughexisting videocontent using avirtual camera andan annotationwindow forcommentary. Userscan post their Divesto the WebDiverserver system togenerate activecollaboration,further repurposing,and discussion.

With the inexorable growth oflow-cost consumer video elec-tronics and broadband net-working, communication-

centric, symmetric video-point-of-view sharingwill eventually supplant broadcast-centric andasymmetric approaches to video content andrepurposing. In sheer volume, the use of existingvideo to share perspectives will likely far outstripvideo repurposing for commercial purposes andfor different device platforms.

Thus, automatic, real-time repurposing of con-tent designed for one technical environment con-figuration (a device or network, for example) tofit other technical environments is but one, albeitimportant, facet of the content repurposing prob-lem. Another fundamental issue in content repur-posing is user-driven content reuse, prompted byusers’ desire to reinterpret content and to com-municate and share their interpretations.

The Digital Interactive Video Exploration and

Reflection (Diver) system provides facilities fordynamic time/space cropping and annotation ofarchival video to support digital video repurpos-ing. Diver lets users create point-of-view videotours of original content in a way that supportssharing, collaboration, and knowledge building.

Diver works like a video camera: a user points,pans, tilts, and zooms with the virtual viewfind-er to create an infinite number of perspectives ona video record. Although other digital video edit-ing and effects tools offer similar repurposing fea-tures (Adobe Premiere’s zoom transition effectsand cropping and Adobe After Effects’ side-by-side group clip compositing, for example), noneoffer a comparable intuitive and easy-to-use inter-face, and few can infinitely repurpose audio andvideo without forcing the user to wait through arendering process.

Diver overviewMuch of our work on Diver involves recording

human activities such as teachers and students ina classroom or research group meetings using aconventional or panoramic digital video camera.Such scenarios involve a broad range of complexhuman interactions of interest to researchers inthe learning and social sciences, such as meetingbehaviors or instructional discourse.

A video-analysis phase follows the video-recording phase.1 Using a mouse, users can zoom,pan, and tilt a virtual camera on an overview ofthe source video. The virtual camera dynamical-ly crops still image clips, or records multiframevideo pathways through the panoramic video tocreate a Diver worksheet. A Dive consists of a setof reorderable panels (inspired by VideoNoter),2

each containing a key frame or thumbnail repre-senting a clip, and a text field that can containan accompanying annotation. Source video cansupport an unlimited number of Dives.

After creating a Dive, a user can upload it toWebDiver, a Web site for interactive browsing,searching, and display of video clips and collab-orative commentary on Dives. Diver automati-cally packages the Dive for WebDiver as an XMLdocument with associated media files. The Dive’sWeb representation includes the key frames,annotations, and video clips. Colleagues can thusshare Dives over the Internet.

Figure 1 gives a schematic representation ofthe recording, Diving, and Web-sharing phases.

Architecture and implementationBecause 4:3-aspect-ratio digital videos are so

54 1070-986X/04/$20.00 © 2004 IEEE Published by the IEEE Computer Society

The DiverProject:InteractiveDigital VideoRepurposing

Roy Pea, Michael Mills, Joseph Rosen, and Kenneth DauberStanford University

Wolfgang EffelsbergUniversity of Mannheim, Germany

Eric HoffertVersatility Software

Content Repurposing

pervasive, they often serve as Diver’s sourcematerial. However, it’s difficult to use such videorecords in social science research. The videogra-pher’s choice of what to include (and what notto include) limits the usefulness of videos record-ed with conventional digital cameras not only forthe original researcher, who can’t recover eventsrelevant to the analysis occurring off camera, butalso for other researchers who might be interest-ed in different aspects of the filmed event.

By supporting panoramic video, Diver avoidsthis problem. Panoramic video has been used inteleconferencing3 and in surveillance, or as onecomponent in an immersive simulation of anevent, such as a football game or concert.4 Weargue that panoramic video is of particular inter-est in all settings where the video material’s pur-pose and application isn’t precisely defined orknown at recording time.

Video recording systemImage resolution is a major technical chal-

lenge in recording panoramic video. For a user tozoom into an area of the panoramic video andstill see sufficient detail, the camera must capturethe video at the highest possible resolution.

In principle, a single-lens system can recordpanoramic video: a spherical mirror, somewhatsimilar to a fisheye lens, collects the light from360 degrees and redirects it onto a camera’scharge-coupled device (CCD) chip. The systemcan then store, compress, and edit the camera’sdigital video stream like any other video stream.Such systems are relatively inexpensive and read-ily available. Examples include the BeHere cam-era (http://www.behere.com) and the cameraused in Ricoh’s Portable Meeting Recorder.5

However, single-lens systems produce low-reso-lution images: the number of pixels on the CCDchip, designed for a small angle, must now suf-fice for surround vision—that is, a much widerangle. Consequently, a user zooming in on anarea in the video will see a low-quality image.

Several recent multilens systems—FullView(http://fullview.com), Fuji’s FlyCam,6 andMicrosoft’s RingCam,7 for example—address thisproblem. They capture scenes using multiplelenses and CCDs with slightly overlapping fieldsof vision and stitch the frames together to con-struct panoramic images. However, these systemsintroduce a new challenge: stitching and dewarp-ing multiple frames in the computer, perhaps inreal time. Multilens systems running at full reso-lution generate a very high bit rate, often too

high to be transferred over a single peripheralcomponent interconnect (PCI) bus.

Diver uses a FullView camera system with fivemirrors and five cameras, and this system feedsthe camera streams to a PC where FullView soft-ware stitches and dewarps the video streams forlive preview (at a reduced frame rate and/orreduced resolution, and always without sound).The FullView system uses three parallel PCI buseson the PC processing the streams to achieve sucha high data transfer rate.

Because of these limitations, we’ve developed atape-based recording system capable of recordingat the full resolution and full frame rate of NTSC-DV (digital video), which is desirable for repur-posing panoramic video (that is, 720 × 480 × 5cameras, at ~30 fps). A system for capturing mul-tichannel sound with a microphone array gener-ates corresponding audio.

To ensure compatibility with 4:3 aspect-ratiovideo and panoramic video content at a varietyof aspect ratios, Diver supports a generalapproach to video analysis, collaboration, andinteraction, allowing for a diversity of aspectratios and resolutions for recorded video materi-al. This provides a flexible approach for record-ing, analyzing, and sharing a broad range ofvideo material independently of the specifics ofthe captured video material.

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1. Shooting

2. Encoding

Quick TimeSource Video

3. Creating the dive

De s k t o p Div e r

my Div e

4. Sharing on Webdiver

my Div e

h t t p : / / Di v e r / my d i v e

my Div e

h t t p : / / Di v e r / my d i v e

my Div e

h t t p : / / Di v e r / my d i v e

Figure 1. Overview of

the Diver video

exploration and

reflection system.

User interface The Diver software consists of the Diver desk-

top application and the WebDiver server system.The desktop application is a native Windowsapplication coded in C++ that builds on Apple’sQuickTime tools and uses the QuickTime videoformat and QuickTime browser plug-in to displayand control the video.

The design rationale for Diver’s user interfaceis rooted in cognitive science and human–com-puter interaction research. Our goal for the toolis to augment the fundamental and social activi-ty of human visual interpretation and commu-nication about what’s interesting or relevant to agiven purpose—namely, looking at a complexscene, noticing events, and commenting on thefocus of attention.

The Diver interface consists of three distinctregions, each corresponding to an element in thelook-notice-comment cycle, as Figure 2 illustrates.

The overview window (look region) providesaccess to the original source material and pro-vides standard video controllers.

The magnified viewing window (notice region)shows the part of the original scene that the userselects by dragging and resizing a rectangle over-lay (the virtual camera) across the overview win-dow, panning over and zooming into regions ofinterest.

This overview/magnified viewing interfaceaims to satisfy the well-known dual-awarenessprinciple of human–computer user interfacedesign: it lets the user zoom in on details of aninformation source while maintaining orienta-tion and context.8,9 Other researchers have

explored related navigational interfaces in exper-imental10–12 and commercial applications ofpanoramic video technology (FullView andBeHere, for example).

As a user drags the virtual camera rectangleacross the video source overview, the viewingwindow gives a dynamically updated and magni-fied view of the circumscribed region. Two but-tons make the viewing selection a flexibleauthoring tool. Mark takes a temporally taggedsnapshot of the viewing window contents andautomatically creates a new panel in the screen’sthird region: the Dive worksheet (commentregion). In addition to a video thumbnail repre-senting a marked frame or clip, a worksheet panelcontains a text field in which users can describethe selection’s noteworthy characteristics.

Pressing the record button creates a newpanel. At the same time, moving the selectionrectangle across the overview window creates arecording of the spatiotemporal selectionshown in the viewing window. Thus the usercan record a dynamic path through the originalsource video. Pressing the record button againends the recording. The user can annotate therecorded pathway clip by entering text in theDive panel.

In creating a unique point-of-view virtual tourof the original video source, the Diver user cre-ates a Dive. The Dive can serve as a storytellingdevice for playing back both the marked loca-tions and the dynamically cropped pathwayrecordings through the original video source andthe records’ annotations.

Panels contain the data elements constitutinga Dive (see Figure 2):

❚ static and dynamic time and space video mark-ers—a static marker points to a single frame inthe video (temporal coordinate) and the loca-tion of the virtual viewfinder in that frame(spatial coordinates); dynamic markers resultfrom recording the virtual camera’stime/space path as the user guides it throughthe source video.

❚ thumbnail representations of time and space videomarkers—thumbnail-sized images copied fromthe source video at the marked time andspace.

❚ annotation text—the commentary associatedwith the marker (that is, the text the usertyped into the panel).

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Figure 2. Diver user

interface. The overview

window (bottom left)

shows the full video

source. The magnified

viewing window (upper

left) shows a selected

image from the scene.

The annotation

window, a.k.a. Dive

worksheet (right) lets

users comment on the

frames or path movies

they create.

❚ time codes—codes indicating the temporalpoint or range of video contained within apanel selection. Static markers take a singletime code; dynamic markers take a range ofcodes.

❚ time/space cropped video clips—thumbnails in apanel that also symbolize portions of thesource video. Double-clicking a thumbnail (ordragging and dropping it back into the view-ing window) repositions the source video atthe corresponding time/space coordinates.

Full-resolution panoramic video recorderDiver’s user interface supports panoramic

video. As Figure 3 demonstrates, the user gets a360-degree horizontal view of the unfoldingscene while the video plays as a “peeled back”cylinder with a wide-aspect ratio.

To accommodate even higher resolution videocapture than native FullView live preview anddirect-to-disk video can achieve, we developed analternative full-resolution video tape-basedrecorder. Our general-purpose Diver recorder sys-tem captures the FullView camera array output atfull resolution (720 × 480 × 5) and full frame rate(~30 fps) to five DV tape recorders (VTRs). TheDiver recorder system later transfers select videotape segments to a PC, where our software reassem-bles in postprocessing the multiple recordings intoseamless full-resolution panoramic movies encod-ed in QuickTime and ready for Diving.

Virtual path moviesThe Diver file format supports the efficient

creation of Dives. As a user drags the virtual cam-era viewfinder across the source overview win-dow, Diver records time (the video time) andspace (a viewing region’s position within thevideo’s border) references, as Figure 4 shows. Thevirtual viewfinder in Figure 4 is rectangular, butit can also be circular or any selection shape.Marking parallel video regions of interest usingmultiple concurrent pathways with the appro-priate user interface is also feasible.

What’s recorded when the user presses therecord button is not a new video; rather, it’s thedigital video collaboratory (.dvc) file informationneeded to replay the dynamically cropped path-way that the virtual camera traced through theoriginal video frame sequence.

When a user plays back a .dvc file, Diver resetsthe current video time and space to the previ-

ously saved coordinates. Before displaying eachframe of video in the virtual camera window,Diver scales the video’s borders (in real time, on-the-fly) to match only the viewing area coordi-nates associated with the same frame (videotime) in the recorded virtual camera path.

Using the .dvc list recording scheme insteadof rendering new video clips has two significantadvantages:

❚ Virtual video clips eliminate the generation ofredundant video files, greatly reducing diskstorage requirements.

❚ No rendering time means vastly improvedperformance. Users can instantly create andplay back dynamic path videos without longvideo-rendering delays.

Dives are thus extremely lightweight glosses onoriginal source content yet they can contain richand compelling viewing experiences.

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Figure 3. Panoramic

video as input for

Diver. The user gets a

360-degree view of the

scene around the

camera’s location.

Figure 4. Graphical representation of the .dvc file format.

The structure and extensibility of the XML-based .dvc file format lets users reformat Divesinto many display and interaction environments.For example, on a lightweight device supportingonly text and image display, a user could extractand show just the text annotations and videoimage thumbnails.

Infinite panoramic audio mixingThe Diver panoramic recording system cap-

tures up to 10 independent audio channels, eachmapped to an associated field of view capturedby the FullView camera. (Near-term enhance-ments will incorporate 16 or more independentaudio channels into the panoramic recordingarray.) Diver embeds these multichannel soundrecordings as navigable QuickTime audio tracksin the postprocessed panoramic movies. Whenplaying back the recordings, Diver can steerpanoramic sound so only the tracks associatedwith the virtual viewfinder’s current focusbecome audible. Thus, Diver users can easilyrepurpose audio recordings and dynamically cre-ate infinite virtual audio mixes.

WebDiver server systemUsers can upload their Dives to a WebDiver

server where others can share them, promotingdialogue and collaboration around video clips.Transforming content for the Web occurs in aseries of client- and server-side automated tasksinvisible to the user. The user chooses the Exportto WebDiver menu option in the desktop Diverapplication, initiating text, image, and video-cliptransformation processes.

The Diver system formats and transfers anno-tation text, time, and space markers and othermetadata associated with each Dive (file names,

file sizes, and so on) to the WebDiver server in anXML format. At the server, PHP scripts and aMySQL database store and retrieve Dive contentfor delivery to client browsers as dynamicallygenerated and JavaScript-enhanced HTML pages.Diver transforms thumbnail images from videobitmaps to JPEG files.

Because QuickTime plug-ins don’t supportreal-time playback of time/space cropped movies,accommodating dynamic playback of suchmovies in Web pages across multiple platformsand browsers would require a custom-codedplug-in for each of the most popular operatingsystems and browsers. As a possible cross-plat-form alternative, we experimented with a DiverJava applet architecture, but found thatQuickTime for Java in its current implementationisn’t robust enough to support time/spacecropped movies. Rather than write our own cus-tom plug-ins, we rendered all Dive video intostandalone QuickTime video clips. Users can playthe videos directly from the WebDiver Web siteusing standard QuickTime players.

During the video clip export process, Diveruses the .dvc file to trace the virtual camera’spath through the time/space cropped video. Itrebuilds the QuickTime clips frame by frame bycopying time/space regions of the source videointo the new standalone files. Diver also convertsthe original video source file to QuickTime in acompressed format of smaller geometry. Theseconversions constitute a technical video repur-posing step in Diver.

Figure 5 shows the XML schema for a Dive. When the desktop Diver finishes the transfor-

mation, the application automatically opens theuser’s Web browser and dynamically generatesand displays a new Web page containing a filetransfer and HTML form frameset. Submittingthe form completes the Dive transmission (rep-resented by the XML file containing Dive meta-data, image thumbnails, and automaticallygenerated video files) from the desktop to theWeb server.

When a user later opens a Dive on theWebDiver site, shown in Figure 6, Diver recon-stitutes the content as HTML and JavaScript,dynamically generating the Web pages from themedia files and XML data. WebDiver pages in thebrowser look similar to desktop Dives and con-tain the same data and media elements.

In addition to the Dive’s author, otherWebDiver users can explore the full source videoused to create it. Moreover, users can collaborate

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<dive id= owner=>

<name></name>

<annotation></annotation>

<video type= id=>

<video_file bytes=></video_file>

</video>

<panel id= order=>

<annotation></annotation>

<video type=>

<time_in></time_in>

<time_out></time_out>

<source_video></source_video>

<video_file bytes=></video_file>

<thumbnail_file

bytes=></thumbnail_file>

</video>

</panel>

</dive>

Figure 5. Dive XML

schema. A <panel>

data block is written

for each panel in the

Dive worksheet.

on Dives by adding comments to the panels inthe manner of a threaded discussion. WebDiverusers can also perform keyword and metadatasearches across all annotations.

Diver usage scenarios and implicationsMultimedia records are an increasingly impor-

tant type of data for researchers in many fieldsbecause they capture the complexity of “mind incontext”—human interactions and behaviors insituations such as the classrooms and the home.Researchers today lack tools for sharing or dis-cussing these data readily with fellow scholarsand practitioners. Diver seeks to bridge this gap,enabling collaborative analysis of learning andteaching video records in a distributed commu-nity of researchers and practitioners.

For example, social scientists can select andannotate video clips of human behavior from theworkplace, home, or learning settings, and sharetheir analyses with distant colleagues. They caninvestigate areas in which video has proven use-ful, such as patterns of student participation ininstructional discourse, uses of diagrams, smallgroup collaboration, and teaching.13–16 Used diag-nostically, Diver can tease out differences in hownovices and experts notice social, behavioral, andphysical phenomena in video. Researchers can useDive panels as structured templates for assessingtrainees in various fields; they can direct users toparticular Diver clips and ask them to answer spe-cific questions. Local or remote experts can pro-vide critiques as threaded comments in WebDiver.For training purposes, experts in a domain couldconstruct Diver videos from Dives created to serveas think-aloud reflective commentaries, offering“guided noticing” help for novices.

More generally, Diver is relevant to any humanactivity domain with dynamic or static media inwhich community engagement in analysis andeducation using those media might bear fruit. Forexample, virtual classroom visits are increasinglyused in teacher education for professional devel-opment (Teachscape.com, Lessonlab.com, andTeachfirst.com, for example).

To ensure that Diver reflects user needs, andto introduce Diver into relevant user communi-ties, we recently held a design kitchen in thelearning and social sciences departments atStanford University. Faculty and graduate stu-dents used Diver to examine their own videodata while the Diver team observed their use ofthe tool and recorded their reactions. The initialuser reaction was positive, with several research

teams already incorporating Diver into theirwork with digital video data—for example, instudies of collaborative learning in mathematics,group discussions of text comprehension, uses ofdiagrams in physics education, and teacherpreparation.

We’re working on a pilot project with severalCalifornia universities in which K–12 teachers useDiver to document and reflect on their teachingpractices in terms of specific quality rubrics forplanning, instruction, assessment, and reflection.

OutlookAlthough our current work focuses on video

records in learning research and educationalpractices, Diver can aid collaborative analysis of abroad array of visual data records, including sim-ulations, 2D and 3D animations, and static worksof art, photography, and text. In addition to thesocial and behavioral sciences, substantive appli-cation areas include medical visualization, astro-nomic data or cosmological models, militarysatellite intelligence, and ethnology and animalbehavior.

Diver-style user-centered video repurposingmight also prove compelling for popular mediawith commercial application involving sportsevents, movies, television shows, and videogaming.

Future technical development includes possi-ble enhancements to the interface to supportsimultaneous display of multiple Dives on thesame source content, a more fluid two-way rela-tion between desktop Diver and WebDiver, and

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Figure 6. A Dive from

the WebDiver site, as it

appears in a browser

window.

solutions to the current limitations on display-ing and authoring time/space cropped videos in abrowser context. These developments supportthe tool’s fundamentally collaborative, commu-nication-oriented nature. MM

AcknowledgmentsDiver, WebDiver, Dive, and Guided Noticing

are trademarks of Stanford University for oursoftware and affiliated services, with patentspending. This work was supported by the USNational Science Foundation (grants 0216334and 0234456) and the Hewlett Foundation. Anyopinions, findings, and conclusions or recom-mendations expressed in this material are thoseof the authors and do not necessarily reflect theviews of its funders.

We used a QuickTime for Windows-basedpanoramic video postprocessing application,developed from camera calibration tables provid-ed by the manufacturer (FullView.com), and withthe programming assistance of Dirk Farin, a visit-ing scholar from the University of Mannheim,Germany. Bob Smith, SCIL’s director of technol-ogy services, made significant design contribu-tions to the Diver panoramic work as did DanNelson, who contributed to the panoramic soundrecording process. Thanks also to Ulrich Neu-mann and the team at the University of SouthernCalifornia’s Integrated Media Systems Center forsharing their expertise and experiences withpanoramic video recording.

References1. B. Jordan and A. Henderson, “Interaction Analysis:

Foundations and Practice,” J. Learning Sciences, vol.

4, 1995, pp. 39-103.

2. J. Roschelle, R.D. Pea, and R. Trigg, VideoNoter: A Tool

for Exploratory Video Analysis, tech. report no. 17, Inst.

for Research on Learning, Palo Alto, Calif., 1990.

3. D. Kimber, J. Foote, and S. Lertsithichai, “FlyAbout:

Spatially Indexed Panoramic Video,” Proc. ACM

Multimedia 2001, ACM Press, 2001, pp. 339-347.

4. T. Pintaric, U. Neumann, and A. Rizzo, “Immersive

Panoramic Video,” Proc. ACM Multimedia 2000,

ACM Press, 2000, pp. 493-494.

5. D. Lee et al., “Portable Meeting Recorder,” Proc. ACM

Multimedia 2002, ACM Press, 2002, pp. 493-502.

6. X. Sun et al., “Panoramic Video Capturing and Com-

pressed Domain Virtual Camera Control,” Proc. ACM

Multimedia 2001, ACM Press, 2001, pp. 329-338.

7. R. Cutler et al., “Distributed Meetings: A Meeting

Capture and Broadcasting System,” Proc. ACM Mul-

timedia 2002, ACM Press, 2002, pp. 503-512.

8. S.K. Card, J.D. Mackinlay, and B. Shneiderman,

eds., Readings in Information Visualization: Using

Vision to Think,” Morgan Kaufmann, 1999.

9. M. Mills et al., “A Magnifier Tool for Video Data,”

Proc. Computer–Human Interactions, ACM Press,

1992, pp. 93-98.

10. L. Teodosio and M.I. Mills, “Panoramic Overviews

for Navigating Real-World Scenes,” Proc. ACM Mul-

timedia 1993, ACM Press, 1993, pp. 359-364.

11. B. Prihavec and F. Solina, “User Interface for Video

Observation over the Internet,” J. Network and

Computer Applications, vol. 21, 1998, pp. 219-237.

12. Y. Rui, G. Gupta, and J.J. Cadiz, “Viewing Meetings

Captured by an Omni-Directional Camera,” tech.

report MSR-TR-2000-97, Microsoft Corp., 2000.

13. B. Barron, “When Smart Groups Fail,” J. Learning

Sciences, vol. 12, 2003, pp. 307-359.

14. J. Frederiksen et al., “Video Portfolio Assessment:

Creating a Framework for Viewing the Functions of

Teaching,” Educational Assessment, vol. 5, no. 4,

1998, pp. 225-297.

15. M. Lampert and D. Loewenberg-Ball, Teaching,

Multimedia and Mathematics: Investigations of Real

Practice, Teachers’ College Press, 1998.

16. M. Ulewicz and A. Beatty, eds., The Power of Video

Technology in Int’l Comparative Research in

Education, Nat’l Research Council, Board on Int’l

Comparative Studies in Education, Board on Test-

ing and Assessment, Center for Education, Wash-

ington, D.C., 2001.

Roy Pea is a professor of education

and learning sciences at Stanford

University, director of the Stanford

Center for Innovations in

Learning (SCIL), and cofounder of

Teachscape.com. His research

interests include applying video analysis technology to

studies in the learning sciences and technology design.

Pea has a DPhil in developmental psychology from

Oxford University as a Rhodes Scholar. He is president-

elect of the International Society of the Learning

Sciences, and a fellow of the National Academy of

Education, the American Psychological Society, and the

Center for Advanced Study in the Behavioral Sciences.

Michael Mills is SCIL’s design

director and a cognitive scientist.

His research interests include

interface, product and interface

design, user studies, and teach-

ing. Mills has a PhD in commu-

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nication with a cognitive science specialization from

McGill University. As principal scientist at Apple

Computer, he was instrumental in the development of

QuickTime and QuicktimeVR, holds 6 interface design

patents in digital video, and has authored many arti-

cles on interface design.

Joseph Rosen is SCIL’s senior

software engineer. His research

interests include software pro-

gramming, interface design, digi-

tal interactive video, computer

graphics, and animation. Rosen

has a master’s degree in interactive telecommunications

from New York University. He also contributed to early

QuickTime research at Apple Computer in the late 1980s.

Kenneth Dauber is SCIL’s acting

deputy research director. His

research interests include sociolo-

gy of culture and science. Dauber

has a PhD in sociology from

University of Arizona. He was a

software architect and director of learning technologies

at Unext.com, an Internet distance education company.

Wolfgang Effelsberg is a profes-

sor of computer science at the

University of Mannheim, with

research and teaching interests in

multimedia technology and com-

puter networks. Effelsberg has a

Dr-Ing degree in computer science from the Technical

University of Darmstadt, Germany. He is a member of

and frequent contributor to the publications of the

ACM, the IEEE and Gesellschaft für Informatik.

Eric Hoffert is the chief executive

officer of Versatility Software. His

research interests include digital

media, collaboration, and com-

munications. Hoffert has MS and

BS degrees in computer science

from New York University. He holds 11 patents and has

published many papers for the IEEE and the ACM.

Readers may contact Pea at Stanford University, Stan-

ford Center for Innovations in Learning, Wallenberg

Hall (Room 232), 450 Serra Mall, Stanford CA 94305-

2055, roypea@stanford.edu.

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