Advidia "A" Series Manual do Utilizador descarregar pdf (Página 55)

Firmware User Manual

Trigger threshold

Look at the moving object entering the area of motion detection: although moving quite slowly, it caused

motion activity – several pixel regions reported a motion that was faster than allowed “speed limit” of

sensitivity (70).

The blue graph on the right side of the

image shows how many percent of pixels

within the motion detection region were

considered as “currently in motion”. The activity panel itself is a timeline – for each moment of time you

can see the height of the blue bars. You may notice that at certain moment the tallest bars in the activity

graph reached about 25% (a quarter of the total height in activity panel) – it means, 25% of this motion

detection area were filled with moving pixels at that moment. By visual observation you can also see that

the object standing inside the motion detection region indeed covers about 25% of its size.

What if the object is really small but moves rather fast (gets triggered by the current sensitivity level)?

For example, we want to detect people but not the cat walking in the room. Although both people and

cat may move with the speed that will trigger motion, they have different size of triggered pixels. For

example, a human passing by the motion detection region will trigger 25% of pixels in that region while

the cat would trigger only 2%. Since we want to have a real alarm in case of human or vehicle passing by

while ignoring birds, cats, butterflies, mice, etc, we need a filter that can define how many percent of

triggered pixels will be considered as a real alarm. This parameter is called trigger threshold. The default

value of trigger threshold is 10%. It means, only the objects that are bigger than 10% of the motion

detection region size and move faster than allowed by sensitivity level (70) will produce actual alarm.

How to choose the most optimal trigger threshold level? The rule of thumb, keep the trigger threshold

as small as possible while not causing false alarms by the moving objects that are not humans or

vehicles.

You can have different sensitivity level and trigger threshold level for each motion detection region.

In order to understand all of the above even better, please refer to the table below containing four

possible combinations of settings using sensitivity level and trigger threshold percentage.

1 2 ... 50 51 52 53 54 55 56 57 58 59 60 ... 111 112

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Advidia "A" Series Manual do Utilizador Página 55