DSDC-GCN: Decoupled Static-Dynamic Co-Occurrence Graph Convolutional Networks for Skeleton-Based Action Recognition

The existing approaches for skeleton-based action recognition based on graph convolutional networks (GCNs) primarily emphasize the construction of human skeletal structure by leveraging inherent connections. However, the static skeletal topology used across all action categories fails to capture discriminative relationships between joint pairs, while current graph structures struggle to model dynamic motion information, limiting their ability to represent both temporal and motion-specific dependencies. To address this limitation, we propose the decoupled static-dynamic co-occurrence graph convolution (DSDC-GConv), which specifically aims to learn and adapt the graph topology by refining the inter-frame and intra-frame joint dependencies through decomposed manner. Additionally, a multi-level context-aware module is proposed to comprehensively model the latent saliencies of multiple domains in skeletal sequences. This module refines the spatial nodes, temporal dynamics, channel-wise characteristics, and motional dependencies within the graph convolution block. Furthermore, a hierarchical densely connected temporal convolution is proposed to enhance the representation of local features through partial dense connections and enrich the temporal information during the convolution process. Findings from our evaluations on five large-scale benchmark datasets (i.e., NTU RGB+D 60, NTU RGB+D 120, Kinetics Skeleton 400, Northwestern-UCLA, PKU-MMD) demonstrate the effectiveness and superiority of our proposed method over competing approaches, with an recognition accuracy of 93.0% and 97.1% on NTU RGB+D 60, 89.9% and 90.6% on NTU RGB+D 120, 38.6% and 63.4% on Kinetics Skeleton 400, 97.4% on Northwestern-UCLA, 97.6% and 63.6% on PKU-MMD.