Anomalous object interaction detection and reporting
Techniques are disclosed for analyzing a scene depicted in an input stream of video frames captured by a video camera. The techniques include evaluating sequence pairs representing segments of object trajectories. Assuming the objects interact, each of the sequences of the sequence pair may be mapped to a sequence cluster of an adaptive resonance theory (ART) network. A rareness value for the pair of sequence clusters may be determined based on learned joint probabilities of sequence cluster pairs. A statistical anomaly model, which may be specific to an interaction type or general to a plurality of interaction types, is used to determine an anomaly temperature, and alerts are issued based at least on the anomaly temperature. In addition, the ART network and the statistical anomaly model are updated based on the current interaction.
1. A processor-implemented method, comprising:
receiving, at a processor, a first sequence and a second sequence, the first sequence associated with a segment of a trajectory of a first object through a scene, and the second sequence associated with a segment of a trajectory of a second object through the scene;
upon determining, via the processor, that the first object and the second object interact with one another, mapping the first sequence to a first sequence cluster and mapping the second sequence to a second sequence cluster;
determining, via the processor, a rareness value for the first sequence cluster and the second sequence cluster, the rareness value given by:
R ij =1− f ij /f max ,
where f ij is an observation frequency associated with the first sequence cluster and the second sequence cluster, and f max is a frequency of a most frequently observed sequence cluster pair;
determining an anomaly temperature based on the rareness value; and
issuing an anomalous object interaction report when the anomaly temperature has a value that exceeds a threshold value.
2. The processor-implemented method of claim 1 , wherein each of the first sequence and the second sequence is normalized to an n-dimensional vector.
3. The processor-implemented method of claim 1 , wherein determining that the first object and the second object interact includes detecting that an edge of a bounding box of the first sequence has come within a predetermined number of pixels of an edge of a bounding box of the second sequence.
4. The processor-implemented method of claim 1 , wherein determining that the first object and the second object interact includes detecting that the trajectory of the first object intersects with the trajectory of the second object.
5. The processor-implemented method of claim 1 , further comprising detecting, based on the first sequence cluster and the second sequence cluster, a tailgating event, the determining the anomaly temperature further based on a tailgating anomaly model.
6. The processor-implemented method of claim 1 , wherein determining the anomaly temperature is performed using a statistical anomaly model.
7. The processor-implemented method of claim 1 , further comprising updating an anomaly model based on the rareness value.
8. An apparatus, comprising:
a processor; and
a memory in operable communication with the processor and storing processor-executable instructions to:
receive a first sequence and a second sequence, the first sequence associated with a segment of a trajectory of a first object through a scene, and the second sequence associated with a segment of a trajectory of a second object through the scene;
upon determining that the first object and the second object interact with one another, mapping the first sequence to a first sequence cluster and mapping the second sequence to a second sequence cluster;
determine a rareness value for the first sequence cluster and the second sequence cluster, the rareness value given by:
R ij =1− f ij /f max ,
where f ij is an observation frequency associated with the first sequence cluster and the second sequence clusters, and f max is a frequency of a most frequently observed sequence cluster pair;
determine an anomaly temperature based on the rareness value; and
issue an anomalous object interaction report if a value of the anomaly temperature exceeds a threshold value.
9. The apparatus of claim 8 , wherein each of the first sequence and the second sequence is normalized to an n-dimensional vector.
10. The apparatus of claim 8 , wherein determining that the first object and the second object interact includes detecting that an edge of a bounding box of the first sequence has come within a predetermined number of pixels of an edge of a bounding box of the second sequence.
11. The apparatus of claim 8 , wherein determining that the first object and the second object interact includes detecting that the trajectory of the first object intersects with the trajectory of the second object.
12. The apparatus of claim 8 , the memory further storing processor-executable instructions to detect, based on the first sequence cluster and the second sequence cluster, a tailgating event, the determining the anomaly temperature further based on a tailgating anomaly model.
13. The apparatus of claim 8 , wherein determining the anomaly temperature is performed using a statistical anomaly model.
14. The apparatus of claim 8 , the memory further storing processor-executable instructions to update an anomaly model based on the rareness value.
15. A non-transitory processor-readable medium storing instructions to:
receiving a first sequence and a second sequence, the first sequence associated with a segment of a trajectory of a first object through a scene, and the second sequence associated with a segment of a trajectory of a second object through the scene;
upon determining that the first object and the second object interact with one another, mapping the first sequence to a first sequence cluster and mapping the second sequence to a second sequence cluster;
determine a rareness value for the first sequence cluster and the second sequence cluster, the rareness value given by:
R ij =1− f ij /f max ,
where f ij is an observation frequency associated with the first sequence cluster and the second sequence cluster, and f max is a frequency of a most frequently observed sequence cluster pair;
determine an anomaly temperature based on the rareness value; and
issue an anomalous object interaction report if the anomaly temperature has a value that exceeds a threshold value.
16. The processor-readable medium of claim 15 , wherein each of the first sequence and the second sequence is normalized to an n-dimensional vector.
17. The processor-readable medium of claim 15 , wherein determining that the first object and the second object interact includes detecting that an edge of a bounding box of the first sequence has come within a predetermined number of pixels of an edge of a bounding box of the second sequence.
18. The processor-readable medium of claim 15 , wherein determining that the first object and the second object interact includes detecting that the trajectory of the first object intersects with the trajectory of the second object.
19. The processor-readable medium of claim 15 , further storing processor-executable instructions to detect, based on the first sequence cluster and the second sequence cluster, a tailgating event, the determining the anomaly temperature further based on a tailgating anomaly model.
20. The processor-readable medium of claim 15 , wherein determining the anomaly temperature is performed using a statistical anomaly model.