  Current state-of-the-art action detection systems are tailored for offline
batch-processing applications. However, for online applications like
human-robot interaction, current systems fall short, either because they only
detect one action per video, or because they assume that the entire video is
available ahead of time. In this work, we introduce a real-time and online
joint-labelling and association algorithm for action detection that can
incrementally construct space-time action tubes on the most challenging action
videos in which different action categories occur concurrently. In contrast to
previous methods, we solve the detection-window association and action
labelling problems jointly in a single pass. We demonstrate superior online
association accuracy and speed (2.2ms per frame) as compared to the current
state-of-the-art offline systems. We further demonstrate that the entire action
detection pipeline can easily be made to work effectively in real-time using
our action tube construction algorithm.
