Global-Local Cross-View Fisher Discrimination for View-Invariant Action Recognition

ABSTRACTView change brings a significant challenge to action representation and recognition due to pose occlusion and deformation. We propose a Global-Local Cross-View Fisher Discrimination (GL-CVFD) algorithm to tackle this problem. In the GL-CVFD approach, we firstly capture the motion trajectory of body joints in action sequences as feature input to weaken the effect of view change. Secondly, we design a Global-Local Cross-View Representation (CVR) learning module, which builds global-level and local-level graphs to link body parts and joints between different views. It can enhance the cross-view information interaction and obtain an effective view-common action representation. Thirdly, we present a Cross-View Fisher Discrimination (CVFD) module, which performs a view-differential operation to separate view-specific action features and modifies the Fisher discriminator to implement view-semantic Fisher contrastive learning. It operates by pulling and pushing on view-specific and view-common action features in the view term to guarantee the validity of the CVR module, then distinguishes view-common action features in the semantic term for view-invariant recognition. Extensive and fair evaluations are implemented in the UESTC, NTU 60, and NTU 120 datasets. Experiment results illustrate that our proposed approach achieves encouraging performance in skeleton-based view-invariant action recognition.