Chen, Lizhe2022-04-292022-04-292022-04-292022-04-22http://hdl.handle.net/10012/18208In recent research, the self-supervised video representation learning methods have achieved improvement by exploring video’s temporal properties, such as playing speeds and temporal order. These works inspire us to exploit a new artificial supervision signal for self-supervised representation learning: the change of video playing speed. Specifically, we formulate two novel speediness-related pretext tasks, i.e. speediness change classification and speediness change localization, that jointly supervise a shared backbone for video representation learn ing. This self-supervision approach solves the tasks altogether and encourages the backbone network to learn local and long-ranged motion and context representations. It outperforms prior arts on multiple downstream tasks, such as action recognition, video retrieval, and action localization.envideo representation learningSelf-supervised LearningContrastive LearningMaster Thesis