Design of a Virtual Auditorium
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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