I. Introduction
The presence of the visual attention mechanism enables humans to quickly identify interested objects with complex external information. Salient object detection (SOD) approaches aim to realize this mechanism. As an important pre-processing method, SOD has seen widespread application in a variety of computer vision tasks, such as video processing [1], image segmentation [2], video action recognition [3], and so on. Although computer technology has made dramatic progress recently, SOD is still a challenging task.