Target-targeted Domain Adaptation for Unsupervised Semantic Segmentation

Semantic segmentation has attracted increasing attention due to its important role in self-driving, and it is often realized by supervised learning with large number of well labeled maps. However, the labeled images are hard to be obtained in most circumstances, and the common way for unsupervised semantic segmentation is usually implemented by transferring the knowledge from source supervised domain to target unsupervised domain. Most researches focus on encouraging target predictions to be closer to the source ones through a weight-sharing network, and achieve certain performance. However, these methods often suffer from the domain shift problem that the networks are often trained towards the source domain and lead to performance degradation. In this paper, we propose a target-targeted domain adaptation approach by focusing the training on target domain. Our model consists of two components: the Image-to-image Translation (IIT) module to translate the source image to target domain and the Target-targeted Segmentation Adaptation (TSA) module to focus the semantic segmentation on target domain. The IIT module deals with image space alignment while the TSA module bridges the domain gap at the segmentation map level. In addition, we design a closed-loop learning to promote each other by employing feedback from TSA to IIT. Extensive experiments on GTA5 and SYNTHIA to Cityscapes demonstrate the effectiveness of our method in domain adaptation of unsupervised semantic segmentation.