Tag Archives: motion

Optimising SecuritySpy’s AI Object Detection

The new AI-powered motion detection features in SecuritySpy version 5 use deep neural networks to detect the presence of humans and vehicles. This allows for highly-accurate triggering of recordings and notifications of just the events that you are interested in.

The AI algorithms output a prediction probability, indicating the likelihood for the presence of a human or vehicle, and you can choose the threshold at which this triggers recording and notifications. Generally, a threshold of 50% gives good results.

However, the accuracy of the AI depends on many factors such as the distance to the subject, lighting, resolution and quality of the camera. You might find that the threshold you have chosen is letting through too many false-positive triggers, or conversely is preventing real motion from generating a trigger.

To see how the AI is performing on your system, create a folder called “AI Predictions” in the SecuritySpy folder within your Home folder (to get to the Home folder, click the Go menu in the Finder and select Home). Then, whenever a video frame is passed through the AI, SecuritySpy will annotate the frame with the motion area and prediction probabilities, and will save it to this folder as an image file. Inspecting these images allows you to determine what the AI is “seeing”, and will therefore allow you to adjust your trigger thresholds for optimum results on your system.

Here are some examples of these annotated images (cropped to just the relevant area):

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How To Achieve Effective Motion Detection

SecuritySpy’s motion detection algorithm employs many techniques in order to accurately detect real motion events while minimising the rate of false-positive detections. But besides an effective algorithm, there are many choices about the setup and configuration of your video surveillance system that will help achieve reliable motion detection – these are outlined below.

1. Camera Angle

How you position and point the camera, as well as the focal length of the lens (how wide-angle it is) makes a big difference to the effectiveness of motion detection. The key points to consider are as follows:

  • The activity you want to capture should be relatively large in the frame. Don’t use a camera with a very wide-angle lens, as this will make objects and people appear very small – too small to trigger motion detection or make out any important features such as faces.
  • Point the camera downwards and don’t include any sky in the frame. At certain times of the day the sun may glare into the camera, which would impair its ability to render the scene with good enough definition, and may even damage its sensor.
  • Include just the area you want to capture in the frame; don’t include any irrelevant areas as this simply wastes the resolution of your camera.

Here is an example of a bad camera angle for motion detection:

Bad Camera Angle

Bad Camera Angle For Motion Detection

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