Dahua IVS Intrusion detection algorithm

[carbonita]

I'm observing some surprising false negatives from an IPC-HDW5231R-ZE -- one of ~100 vehicles passing on the street not alerting. Generally occurs during daylight for vehicles travelling at ~20mph about 30feet from the camera at a 20degree angle of incidence from the lens axis. I have another camera (non Dahua) at the same location with simple motion detection which captures the vehicle. Target filter min/max is 0*0/8191*8191, which alerts on all manner of squirrels, cats, and other critters darting across the street. Anyways, this has gotten me curious about the IVS algorithm. Does anyone have a reference to the IVS intrusion and/or tripwire algorithm used in Dahua cams? I've found some papers (e.g., Efficient method for moving object detection in cluttered background using Gaussian Mixture Model), but can't trace to Dahua implementation.

 

[tigerwillow1]

Some of us think the tripwire algorithm is to trigger when half of the green box crosses the line. This works ok for smaller green boxes but results in no trip for a large green box. I've got one camera location where a mouse crossing the line causes a trip, but a truck doesn't. The bigger issue for me is the green boxes. Sometimes, a clearly visible moving object doesn't cause a box to be created, while on the same camera, something that's difficult for me to see gets a box. With cars I've observed that color matters. The detection characteristics change with different firmware versions.