EventLip: Enhancing Event-Based Lip Reading via Frequency-Aware Spatiotemporal Hypergraph Modeling

Event cameras, with their microsecond-level temporal resolution and sparse visual encoding, provide a transformative paradigm for automatic lip reading (ALR). However, event data inherently lack explicit spatial structure and exhibit a pronounced frequency-domain bias. The low-frequency components fail to capture crucial lip structural information, which fundamentally impedes the modeling of intra-frame topological dependencies and inter-frame semantic evolution-both of which are critical for robust lip reading. To this end, we propose FAST-HG, a Frequency-Aware SpatioTemporal HyperGraph framework specifically designed for event-based lip reading. First, we apply low-frequency perturbation to improve the model's robustness for capturing discriminative features, and integrate adaptive high-frequency filtering to enhance edge-aware representations. Then, we construct a Spatial Region Hypergraph (SRH) and a Temporal Semantic Hypergraph (TSH). The former captures intra-frame topological dependencies among lip regions, while the latter explicitly models inter-frame structural associations throughout the lip movement process, enabling the model to capture discriminative patterns in lip dynamics. Furthermore, we propose a viseme-aware label smoothing strategy, where a novel viseme-level edit distance is designed to quantify visual similarities between classes and guide the construction of soft labels. FAST-HG achieves 79.85% and 84.03% accuracy on the DVS-Lip and DVS-LRW100 datasets, respectively, significantly outperforming prior methods and establishing a new benchmark for event-based lip reading.