Cross-modal learning with multi-modal model for video action recognition based on adaptive weight training

The canonical video action recognition methods usually label categories with numbers or one-hot vectors and train neural networks to classify a fixed set of predefined categories, thereby constraining their ability to recognise complex actions and transferable ability to unseen concepts. In contrast, cross-modal learning can improve the performance of individual modalities. Based on the facts that a better action recogniser can be built by reading the statements used to describe actions, we exploited the recent multimodal foundation model CLIP for action recognition. In this study, an effective Vision-Language action recognition adaptation was implemented based on few-shot examples spanning different modalities. We added semantic information to action categories by treating textual and visual label as training examples for action classifier construction rather than simply labelling them with numbers. Due to the different importance of words in text and video frames, simply averaging all sequential features may result in ignoring keywords or key video frames. To capture sequential and hierarchical representation, a weighted token-wise interaction mechanism was employed to exploit the pair-wise correlations adaptively. Extensive experiments with public datasets show that cross-modal action recognition learning helps for downstream action images classification, in other words, the proposed method can train better action classifiers by reading the sentences describing action itself. The method proposed in this study not only reaches good generalisation and zero-shot/few-shot transfer ability on Out of Distribution (OOD) test sets, but also performs lower computational complexity due to the lightweight interaction mechanism with 84.15% Top-1 accuracy on the Kinetics-400.