Expanding the point: automatic enlargement of presentation video elements

Abstract

We present a system that assists users in viewing videos of lectures on small screen devices, such as cell phones. It automatically identifies semantic units on the slides, such as bullets, groups of bullets, and images. As the participant views the lecture, the system magnifies the appropriate semantic unit while it is the focus of the discussion. The system makes this decision based on cues from laser pointer gestures and spoken words that are read off the slide. It then magnifies the semantic element using the slide image and the homography between the slide image and the video frame. Experiments suggest that the semantic units of laser-based events identified by our algorithm closely match those identified by humans. In the case of identifying bullets through spoken words, results are more limited but are a good starting point for more complex methods. Finally, we show that this kind of magnification has potential for improving learning of technical content from video lectures when the resolution of the video is limited, such as when being viewed on hand held devices.