Towards Source-free Domain Adaptive Semantic Segmentation via Importance-aware and Prototype-contrast Learning

TL;DR

This paper introduces an end-to-end source-free domain adaptation method for semantic segmentation in driving scenes, leveraging importance-aware and prototype-contrast learning to effectively adapt without source data.

Contribution

It proposes a novel IAPC framework that extracts domain-invariant and domain-specific knowledge using importance-aware mechanisms and prototype-contrast strategies, improving adaptation performance.

Findings

Outperforms existing state-of-the-art methods on benchmarks.

Effectively reduces domain shift without source data.

Demonstrates robustness in real-world driving scene segmentation.

Abstract

Domain adaptive semantic segmentation enables robust pixel-wise understanding in real-world driving scenes. Source-free domain adaptation, as a more practical technique, addresses the concerns of data privacy and storage limitations in typical unsupervised domain adaptation methods, making it especially relevant in the context of intelligent vehicles. It utilizes a well-trained source model and unlabeled target data to achieve adaptation in the target domain. However, in the absence of source data and target labels, current solutions cannot sufficiently reduce the impact of domain shift and fully leverage the information from the target data. In this paper, we propose an end-to-end source-free domain adaptation semantic segmentation method via Importance-Aware and Prototype-Contrast (IAPC) learning. The proposed IAPC framework effectively extracts domain-invariant knowledge from the well-trained source model and learns domain-specific knowledge from the unlabeled target domain. Specifically, considering the problem of domain shift in the prediction of the target domain by the source model, we put forward an importance-aware mechanism for the biased target prediction probability distribution to extract domain-invariant knowledge from the source model. We further introduce a prototype-contrast strategy, which includes a prototype-symmetric cross-entropy loss and a prototype-enhanced cross-entropy loss, to learn target intra-domain knowledge without relying on labels. A comprehensive variety of experiments on two domain adaptive semantic segmentation benchmarks demonstrates that the proposed end-to-end IAPC solution outperforms existing state-of-the-art methods. The source code is publicly available at https://github.com/yihong-97/Source-free-IAPC.