VideoBots: Robotic avatars for desktop teleconferencing
|The VideoBot system is designed to enhance the remote presence of teleconference participants. Each remote user is represented by a life-size “talking head” video display mounted on a robotic pedestal with three degrees of freedom. A video camera affixed to the display provides a local image to the remote participant. Moving the robotic display moves the camera in lockstep, and preserves the gaze affordances of face-to-face meetings, where people naturally perceive gaze direction by head orientation. Because the display and camera are mechanically linked, it is easy to tell where the remote participant is looking, because the display is pointed in that direction, which naturally cues local users to the remote user’s gaze direction. A high-quality video link delivers an exceptionally realistic face image and voice quality, increasing the realism and allowing subtle nuances of expression to be conveyed. In addition, the display can move dynamically to attract attention, change gaze direction, indicate degree and direction of interest, and even give motion cues like nodding and bowing.
||It is impossible to look at a VideoBot display and not look
direction of the camera. Studies have shown that the perception of eye
contact is asymmetrical, and that users are much less sensitive to gaze
direction in the
vertical plane. Thus the gaze problem is mitigated to a large extent.
Pointing the display in the same direction as the camera
cues local users to the remote participant’s gaze direction. As
remote user steers the camera to different regions, the display follows
giving immediate feedback to local users about what the remote user can
see. If a VideoBot is directed away from a local user, he or she will
know that the remote user cannot see them.
|VideoBot prototypes consist of 17'' diagonal XVGA color LCD
displays mounted on custom robotic platforms. The power supply has been
removed from the display and installed in a separate enclosure to save
weight. Each of the three axis (rotation, up/down, and in/out) is
driven with a powerful 24V DC motor, using a Solutions Cubed MicroPID
servocontroller. Each motor is equipped with a reduction gear and an
optical position encoder. The servocontroller programmatically drives
the motor to the desired position in a feedback loop. Limit switches
detect when the motion of a particular axis reaches the maximum or
minimum extent. They allow the optical encoders to be calibrated to an
absolute position, and also serve as a fail-safe that inactivates the
motor in the event it is erroneously requested to move beyond its
|We use a blend of custom and off-the-shelf software in the
system. Because the life-size display emphasizes the shortcomings of
typical compressed video, we use the Digital Video format (DV) from a
consumer Sony camcorder via the IEEE 1994 (``FireWire'')
transmitted over the IP protocol using the WIDE DVTS software.
This provides superlative stereo 48 kHz audio and full frame rate 720 X
480 video. Though there is some latency, it is not enough to impact
usability. To match the portrait format of the
VideoBot display, we resort to the simple expedient of rotating the
capture camcorder sideways. For the return audio and video, image
fidelity is less important than small camera size (as the camera must
be mounted on the moveable display). So for the local-to-remote video,
we use a
off-the-shelf USB video camera with 640 X 480 resolution. Return
audio and video is transmitted via the open-source VideoLAN streaming software.
|A WXPython front end
is used to remotely steer the VideoBot. Users see a conventional video
window showing the view from the VideoBot camera, and use a joystick to
control VideoBot movement. Left/righ joystick movement rotates the
VideoBot, while forward/back joystick movement controls either the
up/down axis or, if the trigger button is held, the the in/out axis. If
available, the joystick “rudder control” also controls
in/out axis movement.
|An artist's conception of VideoBot use in a meeting.
(image courtesy Surapong Lertsithichai)
A video demonstration will be available Real Soon Now; in the meanwhile you may watch this VideoBot video (5.4 Mb mpg) taken during system development.
Thanks to Tim Black at Quantalink and Conor McQuaid for help with design and mechanical fabrication.
contact: Jonathan Foote