Multiparty videoconferencing with even a small number of people is often
infeasible due to the high network bandwidth required. Bandwidth can be
significantly reduced if most of the advantages of using full-motion video
can be achieved with low-frame-rate video; unfortunately, the impact of
low-frame-rate video on communication is relatively unexplored. We
implemented a multiparty videoconferencing system that supports
full-motion video, low-frame-rate video where the video is updated only
once every few seconds, and a hybrid scheme where full-motion video is
transmitted when the system detects that a user is making a gesture and
low-frame-rate video is transmitted at all other times. We studied people
using our system for small-group discussions and found that low-frame-rate
video limited people's ability to request to speak or judge when to stop
speaking. The hybrid scheme, conversely, was as effective as full-motion
video for floor control, resulting in a similar number of speaker changes,
while using only ten percent of the bandwidth.
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