  Gait depicts individuals' unique and distinguishing walking patterns and has
become one of the most promising biometric features for human identification.
As a fine-grained recognition task, gait recognition is easily affected by many
factors and usually requires a large amount of completely annotated data that
is costly and insatiable. This paper proposes a large-scale self-supervised
benchmark for gait recognition with contrastive learning, aiming to learn the
general gait representation from massive unlabelled walking videos for
practical applications via offering informative walking priors and diverse
real-world variations. Specifically, we collect a large-scale unlabelled gait
dataset GaitLU-1M consisting of 1.02M walking sequences and propose a
conceptually simple yet empirically powerful baseline model GaitSSB.
Experimentally, we evaluate the pre-trained model on four widely-used gait
benchmarks, CASIA-B, OU-MVLP, GREW and Gait3D with or without transfer
learning. The unsupervised results are comparable to or even better than the
early model-based and GEI-based methods. After transfer learning, our method
outperforms existing methods by a large margin in most cases. Theoretically, we
discuss the critical issues for gait-specific contrastive framework and present
some insights for further study. As far as we know, GaitLU-1M is the first
large-scale unlabelled gait dataset, and GaitSSB is the first method that
achieves remarkable unsupervised results on the aforementioned benchmarks. The
source code of GaitSSB will be integrated into OpenGait which is available at
https://github.com/ShiqiYu/OpenGait.
