Design of a Virtual Auditorium

Milton Chen

Appears in Proceedings of ACM Multimedia 2001


We built a videoconference system called the Virtual Auditorium to support dialog-based distance learning. The instructor can see dozens of students on a tiled wall-sized display and establish eye contact with any student. Telephone-quality audio and television-quality video can be streamed using commodity codecs such as wavelet and MPEG-4. Support for stream migration allows a seamless user interface to span the multiple computers driving the display wall.

We performed user studies on the auditorium parameters. We found that the optimal display wall size must balance two contradictory requirements: subjects prefer larger videos for seeing facial expressions and smaller videos for seeing everyone without head movement. Ideally, each video should have a field of view that spans 14 degrees, which corresponds to a slightly larger than life-size image. At the very least, each video should have a field of view of 6 degrees. We found that a video window should be less than 2.7 degrees horizontally and 9 degrees vertically from the camera in order to maintain the appearance of eye contact for the remote viewer. In addition, we describe a previously unreported gaze phenomenon: a person's expectation determines his perception of eye contact under ambiguous conditions.


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