Continual spatio-temporal graph convolutional networks.

• We proposed a highly efficient online skeleton-based action recognition method. • It reformulates ST-GCN as a Continual Inference Network. • It performs online frame-by-frame predictions in a highly efficient manner. • It achieves up to 26x on-hardware speed-up, and up to 109x FLOP reduction. Graph-based reasoning over skeleton data has emerged as a promising approach for human action recognition. However, the application of prior graph-based methods, which predominantly employ whole temporal sequences as their input, to the setting of online inference entails considerable computational redundancy. In this paper, we tackle this issue by reformulating the Spatio-Temporal Graph Convolutional Neural Network as a Continual Inference Network, which can perform step-by-step predictions in time without repeat frame processing. To evaluate our method, we create a continual version of ST-GCN, Co ST-GCN, alongside two derived methods with different self-attention mechanisms, Co AGCN and Co S-TR. We investigate weight transfer strategies and architectural modifications for inference acceleration, and perform experiments on the NTU RGB+D 60, NTU RGB+D 120, and Kinetics Skeleton 400 datasets. Retaining similar predictive accuracy, we observe up to 109 × reduction in time complexity, on-hardware accelerations of 26 × , and reductions in maximum allocated memory of 52% during online inference. [ABSTRACT FROM AUTHOR]