HoloTrace: LLM-based Bidirectional Causal Knowledge Graph for Edge-Cloud Video Anomaly Detection

Video anomaly detection (VAD) is vital for public safety, yet current approaches struggle with limited generalization, low interpretability, and high resource demands. To address these challenges, we propose HoloTrace, an edge-cloud collaborative VAD system that integrates large language models (LLMs) to construct and update a novel bidirectional causal knowledge graph. At the edge, HoloTrace leverages LLM-based cross-modal understanding and employs Hidden Markov Model (HMM) for bidirectional event reasoning, obtaining anomaly boundaries with low computational overhead. On the cloud side, LLMs are leveraged to dynamically update the Bi-CKG graph with key frames sent from the edge, in order to update causal relationships between events. Additionally, we introduce SVAD, a new large-scale VAD dataset comprising 632 real-world surveillance videos across 10 anomaly types and diverse scenes, with manually labeled frame-level annotations. Experimental results demonstrate that HoloTrace not only achieves the highest accuracy but also enhances interpretability and efficiency, paving the way for more generalizable and explainable video anomaly detection systems.