Alarms allow BrainFrame to notify you when a specified condition happens within a zone. Alarms generate alerts when their condition is met. Alerts are made available through the REST API, and a stream with an active alert is brought to the top of the grid view in the client.
All alarms have an "Active Time", a period during the day where the alarm is allowed to trigger. This can be useful if, for example, you want to be notified if a person is in an area after business hours.
There are two main types of alarm conditions: count-based conditions, and rate-based conditions.
Count-based conditions are triggered based on the number of objects in a zone. The condition may trigger if the number of a certain object class is greater than, less than, equal to, or not equal to a given value. The condition may also specify an attribute value to filter objects by.
The following are examples of count-based conditions:
- If less than 3 people in uniform are in region "Entrance", raise an alarm
- If there is not 1 person in region "Cash Register", raise an alarm
- If there is greater than 0 cars in region "Restricted Parking", raise an alarm
Rate-based conditions are triggered based on a change in the number of objects in a zone over time.
The following are examples of rate-based conditions:
- If greater than 10 people enter region "Main Entrance" within 5 seconds, raise an alarm
- If fewer than 1 car exits region "Parking Lot" within 120 seconds, raise an alarm
Creating an Alarm¶
To create an alarm, open the Task Configuration window for the stream of interest and under the "Add New" section, click the "Alarm" button.
This will bring up the "Alarm Configuration" window. Here you may choose which condition type to use and specify each parameter. The "Condition Type" section is meant to be read like a sentence.
If you don't see any class names available in the second drop-down, make sure that you have at least one plugin loaded that is able to detect objects.
When an alarm is triggered, the alert will appear in that stream's alert log and the stream will be moved to the "Streams with ongoing alerts" section.
By default, a detection is said to be inside a zone if the bottom center point of the detection is in the zone. This bottom center point is referred to as the detection's "intersection point". This default works well for most overhead camera angles, but can be changed to the top, left, right, or center of the detection by changing the "Intersection Point" drop-down in the alarm configuration dialog.