Requirements and recommendations for the Sabotage Detection module🔗

Camera requirements

The video resolution must be at least 0.3 MP; the framerate must be at least 5 frames per second; the image quality must not be reduced significantly by compression, because the high compression rate may negatively affect the work of the defocusing detector.

Aspects of operation

For the detector to trigger, it is required that the changes in the video stream that are indicative of the sabotage of the video surveillance last at least 5 seconds. The detector does not trip in case of brief flashes, darkening, etc. Among other things, this is done to avoid triggering of the detector during the switching of the camera from the day mode to the night mode, because such switching may be accompanied by a significant short-term change of brightness in the frame.

It is allowed to use the detector round-the-clock on the cameras with night mode and on those cameras that switch to such mode. However, the switching to the night mode and back must not take more than 3 — 4 seconds.

The repeated generation of the event cannot happen earlier than in 2 minutes.

After the launch of the module, it is required to wait for 15 seconds for the initial automatic adjustment to be completed.

Aspects of individual detectors

The camera flaring detector is designed for detecting the attempts of flaring a video camera by directing a bright beam of light (e.g. of a flashlight) at its lens. Normally, a camera tries to compensate for the local flaring by darkening the rest of the image. That leads to the indiscernibility of objects in the whole field of view of the camera. For the detector to trip, the specific brightness and area of the flaring spot are required.

This detector is triggered by an attempt to defocus the image.

This detector trips when the lens is covered by foreign objects.

The detector triggers with the following area of overlapping:

  • 50% of the area of the frame is overlapped by a dark stationary object, or by an object placed very close to the lens;

  • 78% of the area of the frame is overlapped by a light moving object, or by an object placed at some distance from the lens.

This detector trips when the camera is turned.

It triggers only when the turning angle exceeds 20 degrees and the turning rate is more than 6 degrees per second.