Evaluation of regularized multi-task leaning algorithms for single/multi-view human action recognition

Regularized multi-task learning (MTL) algorithms have been exploited in the field of pattern recognition and computer vision gradually, which can fully excavate the relationships of different related tasks. Therefore, many dramatically favorable approaches based on regularized MTL have been proposed. In the past decades, although the promising results about human action recognition have been achieved, most of existing action recognition algorithms focus on action descriptors, single/multi-view and multi-modality action recognition, and few works are related with MTL, especial of lacking the systematic evaluation of existing MTL algorithms for human action recognition. Thus, in the paper, seven popular regularized MTL algorithms in which different actions are considered as different tasks, are systematically exploited on two public multi-view action datasets. In detail, dense trajectory features are firstly extracted for each view, and then the shared codebook are constructed for all views by k-means, and then each video is coded by the shared codebook. Moreover, according to different regularized MTL algorithms, all actions or part of actions are considered as related, and then these actions are set to different tasks in MTL. Further, the effectiveness of different number of training samples from different action views is also evaluated for MTL. Large scale experimental results show that: 1) Regularized MTL is very useful for action recognition which can dig the latent relationship among different actions; 2) Not of all human actions are related, if irrelative actions are put together in MTL, its performance will fall; 3) With the increase of the training samples from different views, the relationships about different actions can be fully exploited, and it promotes the accuracy improvement of action recognition.