Databases Reference
In-Depth Information
from users can be interpreted as spatial queries which find arrows or regions closer
to the user's intention. The view in the 3D virtual space means the user's intended
region and can serve as the selective condition of a spatial query. For instance,
while walking through a virtual space, a user can click a 3D arrow icon representing
a video sequence so as to replay it in another window on a screen (Figure 2).
Furthermore, it is possible to incorporate replaying videos into the 3D virtual
space as components of the virtual space (Figure 3, 5). Users can appreciate past
real-world videos in the 3D virtual space. This kind of application is called
Augmented Virtuality
4)
. It provides users with more spatial experience. Another
application of using spatial queries for 3D virtual spaces is to retrieve and replay
videos which show a user's clicked objects in the 3 D virtual space. This application
uses a spatial query to select regions, which correspond to video sequences, including
or intersecting the user's clicked objects.
3
An Experimental System for Spatial Video Browsing
For our experiment, we used two sensors, a GPS and a gyro to generate time-series
spatial data for video sequences which were taken by a digital video camera. We
collected some spatial data for videos taking some scenes of campus festival of
Hiroshima City University held in October 18th and 19th, 1997. The gyro was
precise enough to record the direction of the camera, but the GPS was not precise
to measure the position of the camera. We compensated the position data of the
camera by plotting every one second positions of it on a 2D campus map by hands
later. The zoom ratio can be obtained automatically from a digital camera of the
latest model. To simulate the continuous movement of the camera as real-time 3D
computer graphics animation, we used a method of linear interpolation for the
discrete time-series spatial data such as position, direction and zoom ratio.
Figure 3: Replaying a video on a rectangle plane with a moving camera icon in a 3D virtual
space
We have implemented two typical applications for spatial browsing video data.
