Sequential keypoint density estimator: an overlooked baseline of skeleton-based video anomaly detection

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Hauptverfasser: Delić, Anja, Grcić, Matej, Šegvić, Siniša
Format: Preprint
Veröffentlicht: 2025
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author Delić, Anja
Grcić, Matej
Šegvić, Siniša
author_facet Delić, Anja
Grcić, Matej
Šegvić, Siniša
contents Detecting anomalous human behaviour is an important visual task in safety-critical applications such as healthcare monitoring, workplace safety, or public surveillance. In these contexts, abnormalities are often reflected with unusual human poses. Thus, we propose SeeKer, a method for detecting anomalies in sequences of human skeletons. Our method formulates the skeleton sequence density through autoregressive factorization at the keypoint level. The corresponding conditional distributions represent probable keypoint locations given prior skeletal motion. We formulate the joint distribution of the considered skeleton as causal prediction of conditional Gaussians across its constituent keypoints. A skeleton is flagged as anomalous if its keypoint locations surprise our model (i.e. receive a low density). In practice, our anomaly score is a weighted sum of per-keypoint log-conditionals, where the weights account for the confidence of the underlying keypoint detector. Despite its conceptual simplicity, SeeKer surpasses all previous methods on the UBnormal and MSAD-HR datasets while delivering competitive performance on the ShanghaiTech dataset.
format Preprint
id arxiv_https___arxiv_org_abs_2506_18368
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Sequential keypoint density estimator: an overlooked baseline of skeleton-based video anomaly detection
Delić, Anja
Grcić, Matej
Šegvić, Siniša
Computer Vision and Pattern Recognition
Detecting anomalous human behaviour is an important visual task in safety-critical applications such as healthcare monitoring, workplace safety, or public surveillance. In these contexts, abnormalities are often reflected with unusual human poses. Thus, we propose SeeKer, a method for detecting anomalies in sequences of human skeletons. Our method formulates the skeleton sequence density through autoregressive factorization at the keypoint level. The corresponding conditional distributions represent probable keypoint locations given prior skeletal motion. We formulate the joint distribution of the considered skeleton as causal prediction of conditional Gaussians across its constituent keypoints. A skeleton is flagged as anomalous if its keypoint locations surprise our model (i.e. receive a low density). In practice, our anomaly score is a weighted sum of per-keypoint log-conditionals, where the weights account for the confidence of the underlying keypoint detector. Despite its conceptual simplicity, SeeKer surpasses all previous methods on the UBnormal and MSAD-HR datasets while delivering competitive performance on the ShanghaiTech dataset.
title Sequential keypoint density estimator: an overlooked baseline of skeleton-based video anomaly detection
topic Computer Vision and Pattern Recognition
url https://arxiv.org/abs/2506.18368