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UNDERSTANDING MOTION DETECTION
You can configure MasterControl to recognize various levels and types of
motion by going to the Setup page and clicking the Motion tab. For example,
you can adjust the camera’s sensitivity to motion, configure MasterControl
to ignore subtle changes in light level, or create a motion mask to identify
areas of the video display in which motion should not trigger recording. The
following sections explain how motion detection works in NTSC (the PAL
video standard uses slightly different numbers, as described later in this
section). See the “Configuring Motion Detection” section of this chapter
for information on how to set up MasterControl for motion detection.
THE MOTION DETECTION IMAGE
Each time MasterControl captures and compresses an image, a smaller black-
and-white version of the image is created. This smaller image is used only
for motion detection, then discarded; it is not stored separately from the
compressed data. All motion detection is done using this smaller image.
REFERENCE FRAME
When recording begins from a camera with motion detection active, the first
image of video captured becomes the camera’s
reference frame
, which fol-
lowing images are compared to. The reference frame is replaced periodically
to prevent gradual and inevitable changes—such as light levels during sun-
rise or sunset—from being detected as motion.
The Number of Frames Between Reference setting determines how often the
reference frame is updated. A setting of 100, for example, means that every
100th frame becomes the new reference. The 99th frame would be compared
to the first frame, whereas the 101st frame would be compared to the 100th
frame.
BLOCK DIFFERENCE
Each smaller image captured along with the compressed frame is made up of
330 blocks arranged 22×15. Each time a new image is captured, its smaller
image is compared block by block with the reference frame for that camera. If
the brightness of a block differs from the reference frame by more than the
Sensitivity value, the block is considered changed.
The Sensitivity setting is a percentage times 100. For example, a value of 100
indicates 1 percent, 5000 indicates 50 percent, and so on. A brightness change
Summary of Contents for Dvx 1000
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