Semantic-Aware Multimodal Collaborative Learning for Unsupervised Visible-Infrared Person Re-Identification

Unsupervised visible-infrared person re-identification (VI-ReID) is challenging due to the significant modality gap between visible and infrared images. Most existing methods rely on one-hot clustering pseudo-labels as supervision signals, which often fail to capture the full semantic relationships among samples and are highly susceptible to noise. To address these limitations, we propose a Semantic-aware Multimodal Collaborative Learning (SAMCL) framework for unsupervised VI-ReID. Specifically, a Modality-aware Semantic Fusion (MSF) module is designed to bridge the inter-modality gap by integrating complementary semantic details from both visible and infrared modalities, generating enriched cross-modal supervision signals, for cross-modal collaborative learning. Meanwhile, we present a Dynamic Contrastive Learning (DCL) module to refine intra-modality feature learning by dynamically aligning samples with their neighboring centroids in the feature space, improving clustering reliability and intra-modality feature discrimination. By combining the two modules, SAMCL harnesses multimodal collaboration, minimizes dependence on noisy pseudo-labels, and provides a robust approach to unsupervised VI-ReID. Extensive experiments demonstrate the superiority of our proposed method. For instance, on the SYSU-MM01 dataset, our model achieves a Rank-1 accuracy of 68.68% in the All Search setting, surpassing the state-of-the-art (SOTA) by 3.48%. On the RegDB dataset, it achieves a Rank-1 accuracy of 94.47% in the Visible-to-Infrared setting, outperforming the SOTA by 3.57%. On the LLCM dataset, it achieves a Rank-1 accuracy of 50.6% in the Visible-to-Infrared setting, outperforming the SOTA by 3.7%. The code is available at https://github.com/luoshixi123/SAMCL.