Unsupervised Learning of Video Representations via Dense Trajectory
Clustering
- URL: http://arxiv.org/abs/2006.15731v1
- Date: Sun, 28 Jun 2020 22:23:03 GMT
- Title: Unsupervised Learning of Video Representations via Dense Trajectory
Clustering
- Authors: Pavel Tokmakov, Martial Hebert, Cordelia Schmid
- Abstract summary: This paper addresses the task of unsupervised learning of representations for action recognition in videos.
We first propose to adapt two top performing objectives in this class - instance recognition and local aggregation.
We observe promising performance, but qualitative analysis shows that the learned representations fail to capture motion patterns.
- Score: 86.45054867170795
- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- Abstract: This paper addresses the task of unsupervised learning of representations for
action recognition in videos. Previous works proposed to utilize future
prediction, or other domain-specific objectives to train a network, but
achieved only limited success. In contrast, in the relevant field of image
representation learning, simpler, discrimination-based methods have recently
bridged the gap to fully-supervised performance. We first propose to adapt two
top performing objectives in this class - instance recognition and local
aggregation, to the video domain. In particular, the latter approach iterates
between clustering the videos in the feature space of a network and updating it
to respect the cluster with a non-parametric classification loss. We observe
promising performance, but qualitative analysis shows that the learned
representations fail to capture motion patterns, grouping the videos based on
appearance. To mitigate this issue, we turn to the heuristic-based IDT
descriptors, that were manually designed to encode motion patterns in videos.
We form the clusters in the IDT space, using these descriptors as a an
unsupervised prior in the iterative local aggregation algorithm. Our
experiments demonstrates that this approach outperform prior work on UCF101 and
HMDB51 action recognition benchmarks. We also qualitatively analyze the learned
representations and show that they successfully capture video dynamics.
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