SPD-Updater: Symmetric positive definite manifold geometry based temporal updating for visual object tracking.

Visual object tracking has witnessed continuous advances in recent years along with the exciting developments in backbone networks. In general, all advanced solutions adhere to the template-based tracking framework, which exhibits powerful representative capacity gained via offline training. However, when the target undergoes appearance changes or occlusion, the tracker, which relies on a fixed template defined in the initial frame, struggles to locate it accurately in such complex situations. To achieve online adaptation, recent studies have introduced dynamic templates. Typically, the adopted solution is to compute reliability scores in the traditional Euclidean space to assess the confidence of the dynamic template. However, the Euclidean metric is unreliable to some extent in high-dimensional feature spaces, potentially resulting in a negative impact by involving incorrect dynamic templates. To overcome this problem, we exploit the compact geometric representation capacity of the Symmetric Positive Definite (SPD) manifold to design a novel score prediction module for the tracker update (SPD-Updater). By switching to an SPD manifold metric, we obtain a more accurate and stable dynamic template, thereby enhancing the model capacity to handle complex situations. To validate the reliability of manifold metric in tracking models, we conduct experiments with trackers using different backbones. The experimental results on LaSOT, GOT-10k, TrackingNet, and UAV123 demonstrate the effectiveness of our approach, reflecting the merit of the SPD metric in online tracking adaptation.