Coupling semi-supervised learning and example selection for online object tracking

Training example collection is of great importance for discriminative trackers. Most existing algorithms use a sampling-andlabeling strategy, and treat the training example collection as a task that is independent of classifier learning. However, the examples collected directly by sampling are not intended to be useful for classifier learning. Updating the classifier with these examples might introduce ambiguity to the tracker. In this paper, we introduce an active example selection stage between sampling and labeling, and propose a novel online object tracking algorithm which explicitly couples the objectives of semi-supervised learning and example selection. Our method uses Laplacian Regularized Least Squares (LapRLS) to learn a robust classifier that can sufficiently exploit unlabeled data and preserve the local geometrical structure of feature space. To ensure the high classification confidence of the classifier, we propose an active example selection approach to automatically select the most informative examples for LapRLS. Part of the selected examples that satisfy strict constraints are labeled to enhance the adaptivity of our tracker, which actually provides robust supervisory information to guide semi-supervised learning. With active example selection, we are able to avoid the ambiguity introduced by an independent example collection strategy, and to alleviate the drift problem caused by misaligned examples. Comparison with the state-of-the-art trackers on the comprehensive benchmark demonstrates that our tracking algorithm is more effective and accurate.