Interface Issues for Interactive Navigation and Browsing of Recorded Lectures and Presentations

Being able to visually scan a document that contains a recorded lecture is essential for the usability of such files. In addition, flexible and easy interaction and navigation functionality should be provided to the students in order to improve the overall learning experience. In this paper we discuss the issues involved in these tasks and present a new interaction design that highly improves usability. First, we describe common approaches for browsing, navigating, and reviewing recorded lectures. Then we introduce a new interface design which supports higher interactivity and solves some of the most common problems with regular approaches for these tasks. Motivation – Why Navigation and Browsing of Recorded Lectures is Important Automatic lecture recording and presentation capturing has gained increasing popularity over the last couple of years. Today, many commercial tools exist that make automatic lecture recording an easy, straightforward task. Lecturers at many universities have begun to record their courses on a routinely basis, thus producing a tremendous amount of multimedia documents that can be used for further learning by the students. Many of the commercial systems available today have their roots in earlier research projects related to automatic lecture recording. Most of these projects started already in the middle of the 90s, for example the Cornell/Berkeley Lecture Browser (Mukhopadhyay and Smith (1999)), the Classroom 2000/eClass project (Brotherton and Abowd (2004)), or the Authoring on the Fly system (AOF, Muller and Ottmann (2000)), which was developed by our research group. Over the years, those research projects have not only come up with new solutions for the automatic capturing of presentations but also gained a lot of experience with the usage of the produced files by the students for further learning and studying. For example, at our university many students use them to repeat selected parts of a lecture when doing their homework or when preparing for an exam. One important aspect of this usage is that students usually do not continuously replay the whole recording of a presentation but instead use it very selectively, for example, by reviewing only the parts they haven’t understood completely or that are necessary to solve a particular exercise (Zupancic and Horz (2002)). In fact, using digital, multimedia documents for learning appears to be similar to working with traditional media, for example, books. When reading a novel, one usually starts with the first page and continues reading page by page till the end. In the same way, users watch, for example, a movie on a DVD linearly from the beginning to its end without much interaction during its replay. On the other hand, when a text book is used for learning, its content is usually processed more selectively: Chapters of particular interest are accessed directly, parts of minor interest are scanned quickly or skipped completely while more complicated topics are re-read over and over again, sometimes sentence by sentence, and so on. Similarly, students want to “work” with multimedia data, such as lecture recordings, when they use it for learning. They want to quickly skim the file in order to locate parts of particular relevance and to skip portions of minor interest. They need to be able to set back and replay a part they just listened to but didn’t understand. They want to examine complicated parts of the content in more detail than other portions of the file, and so on. Consequently, system designers have to offer comfortable, flexible, and easy browsing, navigation, and interaction support in the player software in order to provide the highest possible usability for the students. Common Approaches for Visual Navigation and Browsing of Lecture Recordings Most systems for replay of recorded presentations offer a thumbnail overview of the slides used in the lecture. Each of these thumbnails is usually linked to the corresponding position in the multimedia file that contains the recording (compare Figure 1a). In a similar way as static keyframes are often represented in order to facilitate browsing and navigation of video data (compare Girgensohn et al. (2001), for example), thumbnails of slides can be used to quickly scan the recorded lecture’s content, to identify relevant parts, and to access them directly by clicking on the respective thumbnail icon. However, such approaches have significant disadvantages. The minimized display of the slides reduces readability making it sometimes hard to identify its content. In addition, thumbnails can only provide a static representation of the continuous media signal. This is no problem, if the visual data stream of the lecture recording just contains slides whose content is not changing but static between the transition of two slides. However, the full power of modern systems for presentation recording lie in their ability to record continuously changing information as well, such as handwritten annotations made on a slide. A static representation of these annotations removes information contained in the original signal and makes browsing of the content much harder. For example, in the case illustrated in Figure 1, it is impossible to decided in which order the annotations on the graphics were made by just looking at its static representation due to the removal of the temporal information. However, this order might be important, if not essential for the learning process of the students. Maybe the most critical disadvantage of thumbnail representations is that they restrict navigation to specific entry points of the file, namely the transitions from one slide to another. Consider a situation where a student wants to go back and repeat the last one or two sentences that have just been replayed. If navigation is only supported via thumbnails, one has to go back to the position where the corresponding slide appeared on the screen for the first time, what in the worst case might be as much as a several minutes. This is truly not a comfortable and flexible way to interact with the system or the corresponding data. the corresponding thumbnail single slides by clicking on and navigation between of the document’s content They enable quick scanning the synchronization model random accessibility provided by (b) Time-based slider interface data stream due to the real-time displays any change of the visual Moving the slider knob immediately icons (a) Thumbnails of the slides Figure 1: Original interface design of our player software which offers different possibilities to browse and navigate through a lecture recording, for example, (a) by using the thumbnail representation of the slides or (b) by using the time-based slider that offers real-time random access to any position within the document.