Single-Stream Extractor Network With Contrastive Pre-Training for Remote-Sensing Change Captioning

Remote sensing (RS) image change captioning is a visual semantic understanding task that has received increasing attention. The change captioning methods are required to understand the visual information of the images and capture the most significant difference between them, then describe it in natural language. Most existing methods mainly focus on improving the difference feature encoder or language decoder, while ignoring the visual feature extractor. The current feature extractors suffer from several issues, including 1) domain gap between pre-training on single temporal natural images and downstream bi-temporal RS task, 2) limited difference feature modeling in the implicit single-stream network, and 3) high computational costs caused by extracting features for each temporal phase image under the dual-stream extractor. To address these issues, we propose a Single-stream Extractor Network (SEN). It consists of a single-stream extractor pre-trained on bi-temporal RS images using contrastive learning to mitigate the domain gap and high computational cost. Additionally, to improve feature modeling for difference information, we propose a shallow feature embedding (SFE) module and a cross attention guided difference (CAGD) module, which enhance the representation of temporal features and extract the difference features explicitly. Extensive experiments and visualizations demonstrate the effectiveness and advanced performance of SEN. The code and model weights are available at https://github.com/mrazhou/SEN.