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Dawa Sewbalak
22.2.3.1 Parameters Panel
The facilities provided within the Parameters panel allow the operator to set tracking
sensitivity and the range of facial sizes for tracking operations.
22.2.3.1.1
Follow Threshold
Determines the confidence threshold associated with the knowbot structure for determining
whether the segmented region corresponds to a face. If the confidence remains above this
threshold, the knowbot will continue to follow the face on subsequent video frames.
22.2.3.1.2
Maximum Size
This text box sets the upper size limit for faces that are tracked. This size limit is applied for
tracking during all modes of operation (i.e. enrollment, classify and verify ). The size of the
facial tracking box is established as a fraction of the height of the video frame.
22.2.3.1.3
Minimum Size
This text box sets the lower size limit for faces that are tracked. This size limit is applied for
tracking during all modes of operation (i.e. enrollment, classify and verify ). The size of the
facial tracking box is established as a fraction of the height of the video frame.
22.2.3.2 Mask Thresholds Panel
The panel entitled "Mask Thresholds" panel pertains to a series of masks that are applied
over the video frame, sectioned into 16 x 16 regions. Each region of the video frame is
evaluated separately for variance, frame to frame movement and color content. Thresholds
are applied to these measurements in order to mask out regions of the video frame from the
tracking subsystem. Proper use of masks can significantly improve tracking speed and
performance. It should also be noted that the effect of the masks may be viewed by clicking
on the "View/Show Masks/All" menu items. Descriptions of the parameters contained within
the "Mask Thresholds" panel are provided below:
22.2.3.2.1
Variance
The variance measurement within each region is normalized by variance across the entire
video frame. This set point is used when the variation over time in overall lighting intensity is
large. If relative pixel intensity variance is less than this threshold, the region will be masked
out.
22.2.3.2.2
Abs Variance
Similar to the "Variance" threshold, however the threshold for masking out regions of the
video frame based upon an absolute measure of pixel intensity variance. If intensity variance
is less than this threshold, the region will be masked out.
22.2.3.2.3
Movement
Sets a difference threshold for frame-to-frame pixel intensity. This value is used to detect
motion. If the frame-to-frame difference in pixel intensity is less than this threshold, the
region will be masked out.
22.2.3.2.4
Face Color
Regions of the image may be masked out based upon color content. This value sets the
mask threshold for skin tone. The color scoring method has been tuned to recognize skin
tone among all ethnic types. The valid range for this parameter is -1 to +1. Lower values will
cause a greater region of the video frame to be masked out.
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Power Automation
Printed 5/29/2005