1 Introduction  
2 Third-Person Action Recognition  
2.1 Single Modality-Based HAR  
2.2 Multimodal Fusion  
2.3 Multimodal HAR  
3 Egocentric Action Recognition  
3.1 Single Modality-Based EAR  
3.2 Multimodal EAR  
4 Datasets and Performance  
4.1 Datasets  
4.2 Performance  
5 Conclusion