Mining Semantics-Preserving Attention for Group Activity Recognition

In this paper, we propose a Semantics-Preserving Teacher-Student (SPTS) model for group activity recognition in videos, which aims to mine the semantics-preserving attention to automatically seek the key people and discard the misleading people. Conventional methods usually aggregate the features extracted from individual persons by pooling operations, which cannot fully explore the contextual information for group activity recognition. To address this, our SPTS networks first learn a Teacher Network in semantic domain, which classifies the word of group activity based on the words of individual actions. Then we carefully design a Student Network in vision domain, which recognizes the group activity according to the input videos, and enforce the Student Network to mimic the Teacher Network during the learning process. In this way, we allocate semantics-preserving attention to different people, which adequately explores the contextual information of different people and requires no extra labelled data. Experimental results on two widely used benchmarks for group activity recognition clearly show the superior performance of our method in comparisons with the state-of-the-arts.