Improving Feature Discrimination for Object Tracking by Structural-similarity-based Metric Learning

Existing approaches usually form the tracking task as an appearance matching procedure. However, the discrimination ability of appearance features is insufficient in these trackers, which is caused by their weak feature supervision constraints and inadequate exploitation of spatial contexts. To tackle this issue, this article proposes a novel appearance matching tracking (AMT) method to strengthen the feature restraints and capture discriminative spatial representations. Specifically, we first utilize a triplet structural loss function, which improves the learning capability of features by applying a structural similarity constraint with a triplet metric format on the features. It leverages feature statistics to capture the complex interactions of visual parts. Second, we put forward an adaptive matching module that exploits the dual spatial enhancement module to reinforce target feature discrimination. This not only boosts the representation ability of spatial context but also realizes spatially dynamic feature selection by attending to target deformation information. Moreover, this model introduces a simple but effective matching unit to intuitively evaluate the relative appearance differences between the target and the proposals. In addition, with the obtained discriminative features, AMT is capable of providing precise localization for the target. Therefore, the impact of spatial suppression imposed by window functions can be alleviated, allowing for effective tracking of high-speed moving objects. Extensive experiments prove that AMT outperforms state-of-the-art methods on six public datasets and demonstrate the effectiveness of each component in AMT.