  With the prevalence of the commodity depth cameras, the new paradigm of user
interfaces based on 3D motion capturing and recognition have dramatically
changed the way of interactions between human and computers. Human action
recognition, as one of the key components in these devices, plays an important
role to guarantee the quality of user experience. Although the model-driven
methods have achieved huge success, they cannot provide a scalable solution for
efficiently storing, retrieving and recognizing actions in the large-scale
applications. These models are also vulnerable to the temporal translation and
warping, as well as the variations in motion scales and execution rates. To
address these challenges, we propose to treat the 3D human action recognition
as a video-level hashing problem and propose a novel First-Take-All (FTA)
Hashing algorithm capable of hashing the entire video into hash codes of fixed
length. We demonstrate that this FTA algorithm produces a compact
representation of the video invariant to the above mentioned variations,
through which action recognition can be solved by an efficient nearest neighbor
search by the Hamming distance between the FTA hash codes. Experiments on the
public 3D human action datasets shows that the FTA algorithm can reach a
recognition accuracy higher than 80%, with about 15 bits per frame considering
there are 65 frames per video over the datasets.
