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Optical flow is widely used in human action recognition. However, the influence of complex background on optical flow often leads to low recognition efficiency. To deal with this issue, an optical flow-based physical feature-driven action recognition framework is proposed in this paper. We first calculate the original dense optical flow field. Then, for reducing computational burden, joint action relevance that can eliminate the pseudo-optical flow in complex background is developed. After that, a more state flow field is obtained by local spatial–temporal thermal diffusion processing. On this basis, we design a feature descriptor that takes the divergence, curl and gradient features of flow field into consideration. Finally, we adopt Fisher vector to encode descriptors for classification. Experimental on HMDB51, KTH and UCF101 datasets proves that actions in complex background can be recognized accurately by the proposed framework, which outperforms the already developed methods. [ABSTRACT FROM AUTHOR]

Human action recognition (HAR) is one of the most challenging tasks in the field of computer vision due to complex backgrounds and ambiguity action, etc. To tackle these issues, we propose a novel action recognition framework called Semantic Feature and High-order Physical Feature Fusion (SF-HPFF). Concretely, we first calculate attention pooling module with a low-rank approximation to remove the information of irrelevant complex backgrounds and thus capture the interested target motion region. On this basis, motion features based on the physical characteristics of flow field and semantic features based on word embedding are developed to distinguish ambiguity behaviors. These features are of low dimension and high discrimination, which help to reduce computation burden significantly while maintaining an excellent recognition performance. Finally, cascaded convolutional fusion network is adopted to fuse features and accomplish classification. Multiple experiment results validate that the proposed SF-HPFF outperforms the state-of-art action recognition methods. [ABSTRACT FROM AUTHOR]