The ePresence Interactive Webcasting and Archiving System: Technology Overview and Current Research Issues (2004)

In contrast to video conferencing, webcasting supports scaleable Internet visual communications, yet it is typically viewed as an ephemeral one-way broadcast medium. We have developed a system design to support interactive webcasts that are accessible in real-time by remote viewers and retrospectively by archive viewers who can browse and search for what they want to see. ePresence is an open source system implemented using .NET technology that currently works with Windows and Linux servers and supports a wide variety of machines, operating systems, browsers, media engines, and bandwidths. We discuss current features of ePresence, its architecture and implementation, research intended to provide new capabilities, and the motivation for an open source release. Further details about the system’s functionality, interface, and applications may be found in the companion paper “ePresence: An Open Source Interactive Webcasting and Archiving System for eLearning” by Rankin, Baecker, and Wolf. The ePresence System ePresence is an integrated hardware and software webcasting and event archiving system. To facilitate scaleable communications and knowledge sharing at a distance, we are engaged in research to make Internet visual communications: • engaging, delivering rich media • interactive • accessible in real-time and via archives • useful for knowledge building and sharing. The result has been a viable and innovative webcasting infrastructure called ePresence (Baecker, 2002; Baecker, 2003; Baecker, et al., 2003). ePresence currently includes support for: • video, audio, slide, and live computer desktop demos • slide review • moderated chat, private messages, and the submission of questions; and • the automated creation of structured, navigable, searchable event archives. ePresence also allows configurable live and archive interfaces through tailorable “skins”. Video, audio, slides, and computer desktops are automatically synchronized by the system. The “remote desktop” capability supports transmission of live 600X800 screen capture streams of live software demos and “Web tours” from the presenter’s computer. Web links can also be sent by the speaker and synchronized with the video. Slide controls allow a remote viewer to review any slide already presented by the speaker. The chat system supports public chat, private messages, and questions to the speaker. The archives interface allows retrospective navigation and browsing through a webcast using an outline of the logical structure of the talk and its slides and live demo sessions. Two levels of structure information are supported — chapters (sections of a talk) and slides. Slide titles are picked up automatically from Powerpoint in case it is used; chapter titles are input by the moderator during the talk and can if need be updated afterwards. Archive viewers can also navigate using a timeline. Additionally, we allow searching based on key words that appear in Powerpoint slides. ePresence has been developed with full attention to valuable prior research described in Brotherton and Abowd (2004), Cadiz, et al. (2000), Hurst, et al. (2001), Isaacs, Mooris, and Rodriguez (1994), Jancke, Grudin, and Gupta (2000), Rowe, et al. (2001), Scott and Eisenstadt (1998), and Wactlar, et al. (1999). A more complete literature review appears in Baecker (2003). More detail about the system capabilities, interface, style of usage, and applications may be found in the companion paper Rankin, Baecker, and Wolf (2004). System Architecture and Implementation The system is implemented using .NET. The server software runs under Windows or Linux. Webcast can be viewed on client personal computers running the Linux, Windows 98/2000/2003/XP, and Mac 9.x or OS/X operating systems, and the Internet Explorer, Netscape Navigator, Mozilla, Opera and Safari 1.2 browsers, and using either Real Media or Windows Media live streaming. Archives may be produced in Real Media, Windows Media, and MPEG4 formats. The architecture of our highly modular system may be portrayed as in Figures 1 and 2. The reader may find the following explanation of what all the modules do and how they fit together more understandable if she also refers to the discussion of features and interfaces that appears in the companion paper Rankin, Baecker, and Wolf (2004). Figure 1: Current ePresence system architecture for live webcast Interactive Webcasting (Live) An ePresence live webcast is created by a speaker, an operator, and a moderator. These can be different individuals or the same person depending upon the scale of the event. The ePresence Mobile Station (4) includes several live media encoding and capturing software applications (e.g., Windows or Real Media) controlled by the operator (3) or speaker (7) via a single unified remote control interface. The remote control interface has been developed for different internet-connected devices (Laptops, tablet Pcs, and PDAs). The transport protocol used for remote control is an XML Remote Procedure Call mechanism called SOAP (Simple Object Accessing Protocol, http://www.w3.org/TR/soap/) (12). The operator can perform the following operations remotely: initiate live broadcast, start or stop archiving session, control slides transmission, submit URLs, and initiate multiple live software demo sessions. The speaker may give a talk to a local audience or remotely via a video telephone or videoconferencing (1). This allows us to webcast a meeting that is being held via videoconference. Web-based slide controlling and projecting (7) software allows having multiple distributed audiences listening and following the slide presentation in real time. The moderator interface (10) supports a local moderator who is watching the webcast, sending public announcements to a web audience, and submitting notes (chapter titles) to the archiving application. The moderator works as a communication “bridge” between the speaker and web audience transferring questions and comments on behalf of remote participants. An ePresence webcast is typically viewed by both a local audience (2) and a live web audience (6). The web audience receives video and audio (13) of the speaker(s) from the streaming servers (5), a synchronized slide presentation stream (18) or a screen capture stream (14) from the presenter’s computer, and web URLs (15). Remote viewers can also submit questions to the speaker (directly or via the moderator), have public or private text based dialogs (16), and review the slides that have been already presented. The presentation tier (9) is implemented as a set of web-based applications running on the .NET framework and several database engines (11). The server application has been recently ported from Windows to the Linux platform, and now supports Apache and MySQL software as a backend. The live interface (9) has been developed as a set of templates (“UI skins”) that support different layouts, media formats, video resolutions and other features. The operator can choose the most suitable template depending on the content of the talk. Adopters of the ePresence system can easily develop their own skins using XML, HTML, and several scripting technologies. Figure 2: Producing an archive of an ePresence webcast Archiving and Publishing a Webcast The webcast data (4) such as video (1), slides (3) and event streams (2) is automatically captured during the live webcast. The events stream data includes time stamp information of slides and chapters submitted during the live webcast. Event streams can be updated (5) after the webcast using the ePresence Producer application (12). The operator can add additional keywords to enhance search, update slide synchronization data, edit chapter and slide titles, and replay the event with all synchronized materials before publishing the archive. The ePresence Producer software also allows encoding the captured video in different popular streaming formats (6), automatic uploading to a streaming server (7), automatic creation and publishing of web archives (8), and production of multimedia CDs (9). The software provides a selection of archive templates. The templates mechanism is based on XML/XSLT technology (http://www.w3.org/XML/, http://www.w3.org/TR/xslt). The published archive becomes automatically available on the ePresence website (10). It includes video player, slide frame, interactive timeline component, search tool, interactive table of contents, and threaded discussion board. Every archive exposes its keywords through the XML web services. This makes it easy to integrate the archives into different document repositories, “learning object” banks, and other searchable data storage systems.