Compact Bilinear Augmented Query Structured Attention for Sport Highlights Classification

Understanding fine-grained activities, such as sport highlights, is a problem being overlooked and receives considerably less research attention. Potential reasons include absences of specific fine-grained action benchmark datasets, research preferences to general super-categorical activities classification, and challenges of large visual similarities between fine-grained actions. To tackle these, we collect and manually annotate two sport highlights datasets, i.e., Basketball-8 Soccer-10, for fine-grained action classification. Sample clips in the datasets are annotated with professional sub-categorical actions like "dunk", "goalkeeping"and etc. We also propose a Compact Bilinear Augmented Query Structured Attention (CBA-QSA) module and stack it on top of general three-dimensional neural networks in a plug-and-play manner to emphasize important spatio-temporal clues in highlight clips. Specifically, we adapt the hierarchical attention neural networks, which contain learnable query-scheme, on the video to identify discriminative spatial/temporal visual clues within highlight clips. We name this altered attention which separately learns a query for spatial/temporal feature as query structured attention (QSA). Furthermore, we inflate bilinear mapping, which is a mature technique to represent local pairwise interactions for image-level fine-grained classification, on video understanding. In detail, we extend its compact version (i.e., compact bilinear mapping (CBM) based on TensorSketch) to deal with the three-dimensional video signal for modeling local pairwise motion information. We eventually incorporate CBM and QSA together to form CBA-QSA neural networks for fine-grained sport highlights classifications. Experimental results demonstrate that CBA-QSA improves the general state-of-the-arts on Basketball-8 and Soccer-10 datasets.