Information Technology Reference
In-Depth Information
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Shape 3-D Descriptor
The Shape 3-D descriptor specifies the shape of 3-D mesh mod-
els. It uses a function of two principal curvatures. However, it is
strongly dependent on the accuracy of estimates of the principal
curvatures.
11.2.4 Motion Feature Descriptors
Although color, texture, and shape feature descriptors can be used in
indexing video frames, motion features in videos can provide more visual
information about motion characteristics in video sequences. The more
detailed descriptions of motion features and feature extraction are beyond
the limitations of this chapter and can be found in ISO/IEC information
technology [1].
The MPEG-7 standard defines several feature descriptors based on
motion.
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Camera Motion Descriptor
The camera motion descriptor specifies 3-D camera motion parame-
ters that automatically are extracted or generated by capture devices.
It supports the following basic camera operations: fixed, panning,
tracking, tilting, booming, zooming, dolling, and rolling. The sub-
shots with all frames characterized by a particular type of cam-
era motion determine the building blocks for this camera motion
descriptor.
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Motion Trajectory Descriptor
The motion trajectory descriptor specifies the motion trajectory of a
moving region, defined as the spatio-temporal replacement of one of
its representative points such as its centroid. It can be used to check
if objects enter sensitive areas for surveillance videos.
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Parmetric Motion Descriptor
The parmetric motion descriptor specifies the motion of objects in
video sequences, as well as global motion. The descriptor character-
izes the evolution of arbitrarily shaped regions over time in terms of
a 2-D geometric transform. The descriptor describes translational,
ration-scaling, affine, perspective, and quadratic models of 2-D
motion from one frame to the next.
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Motion Activity Descriptor
The motion activity descriptor specifies the motion activities includ-
ing intensity, direction, spatial distribution, spatial localization, and
