Optelecom-nkf Siqura C-54 E-MC User Manual page 66

Using the internal web pages
Note on Advanced VMD settings: Motion is detected by comparing the current frame with a reference
image (e.g. a previous frame) and calculating the difference between the two. The value you enter for
the Event window size parameter determines how many frames are evaluated for VMD purposes at a
time. Not all frames from the original video stream are used for VMD. Only 1 divided by the value set for
the frame rate divider frames are evaluated.
A VMD event becomes active when, within the Event window, the number of frames with motion exceeds
a configurable value, the Event window hi mark. After this, the VMD event will remain active until the
number of frames with motion drops below another configurable value, the Event window low mark.
frame
with
motion
X = Event window size
VMD alarm becomes active when in at least Y out of X frames motion is detected.
VMD alarm becomes inactive when in at least Z out of X frames no motion is detected.
No VMD alarm VMD alarm
Y = Event window hi mark
Figure 7.45 VMD alarm and Event window hi/low mark
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No VMD alarm
Z = Event window low mark
X
Y
Z
0