Crowd anomaly detection

A video security system comprising:

• an image sensor configured to capture video data;
• and
• an electronic processor configured to detect an anomaly by:
• obtaining the video data captured using the image sensor;
• determining a number of people detected within each of a plurality of frames of the video data;
• for each moment t, determining an average number of people n1(t) over a time interval (t-Δt1, t), where Δt1 is greater than or equal to the moment t;
• for each moment t, determining an average number of people n2(t) over a time interval (t-Δt2, t), where Δt2 is greater than or equal to Δt1;
• for each moment t, determining a change Δn in an average number of people based on at least one selected from the group consisting of the average number of people n1(t) and the average number of people n2(t);
• for each moment t, selecting one of a plurality of first histograms based on the average number of people n2(t);
• for each moment t, determining a probability ρ of the change Δn in the average number of people based on the selected one of the plurality of first histograms;
• determining whether the probability ρ is less than a threshold probability ρ*;
• and
• in response to determining that the probability ρ is less than a threshold probability ρ*, generating an alert indicating that an anomalous crowd growth is detected.

A method for detecting an anomaly in a region of interest of a camera, the method comprising:

• capturing video data using an image sensor;
• obtaining the video data captured using the image sensor;
• determining a number of people detected in each of a plurality of frames of the video data;
• for each moment t, determining an average number of people n over a time interval (t-Δt1, t), where Δt1 is greater than or equal to the moment t;
• for each non-overlapping time interval Δt1, updating a histogram based on the average number of people for the time interval Δt1;
• at each moment t, determining a probability ρ associated with the average number of people n over the time interval (t-Δt1, t) using the histogram;
• and
• in response to determining that the probability ρ of the average number of people n over the time interval (t-Δt1, t) is less than a threshold probability ρ*, generating an alert indicating that an anomalous crowd size is detected.