Crowd Density
How it works
The Crowd Density rule generates an event when the number of people in a defined region of interest reaches or exceeds a configured threshold for a set period of time (the "dwell time"). It is built for scenes where people are dense enough that counting individuals one by one is unreliable — for example train stations, city squares, transit hubs, public gatherings, and demonstrations. Rather than tracking each person separately, it estimates the overall crowd in the area, which makes it suited to busy, high-occupancy scenes.
How it detects
Crowd Density uses a dedicated crowd-estimation model (the "crowd" object type) rather than the standard per-person detector. It analyzes full-size frames on a fixed schedule, sampling the whole scene periodically instead of reacting to individual movement. Because of this, its behavior is not tied to how much activity is happening in the scene — it runs on the same cadence whether the area is quiet or busy. When the estimated number of people in the region of interest crosses the threshold you set and stays above it for the dwell time, the rule generates an event with a crowd overlay on the scene. Note: Crowd Density is different from Crowd Statistics. Crowd Statistics is the reporting feature that shows a live per-head dot overlay and a running count over time; Crowd Density is the real-time rule that raises an event when a crowd threshold is exceeded.
How to set up
- Open the camera you want to configure and add a new rule.
- Select "Crowd Density" as the rule type.
- Draw the region of interest on the scene — the area to monitor for crowding.
- Set the people threshold — the number of people that must be present in the region before an event is generated.
- Set the dwell time — how long the crowd must remain at or above the threshold before the event triggers.
- Save and activate the rule. It can run alongside other rules on the same camera and be scheduled to active hours.
What to expect
- An event is generated once the estimated crowd meets your threshold for the full dwell time.
- Crowd Density events are shown with a scene overlay (distinct from the per-person dots used by Crowd Statistics).
- The rule performs best in genuinely dense scenes. In sparse scenes where people are easily separable, the per-person rules (Grouping, People Counting) are usually a better fit.
- Because detection runs on a fixed schedule over the full frame, very brief crowd spikes shorter than the sampling interval may not register.