Bridging the Gap: Multi-Level Cross-Modality Joint Alignment for Visible-Infrared Person Re-Identification

Visible-Infrared person Re-IDentification (VI-ReID) is a challenging cross-modality image retrieval task that aims to match pedestrians’ images across visible and infrared cameras. To solve the modality gap, existing mainstream methods adopt a learning paradigm converting the image retrieval task into an image classification task with cross-entropy loss and auxiliary metric learning losses. These losses follow the strategy of adjusting the distribution of extracted embeddings to reduce the intra-class distance and increase the inter-class distance. However, such objectives do not precisely correspond to the final test setting of the retrieval task, resulting in a new gap at the optimization level. By rethinking these keys of VI-ReID, we propose a simple and effective method, the Multi-level Cross-modality Joint Alignment (MCJA), bridging both the modality and objective-level gap. For the former, we design the Visible-Infrared Modality Coordinator in the image space and propose the Modality Distribution Adapter in the feature space, effectively reducing modality discrepancy of the feature extraction process. For the latter, we introduce a new Cross-Modality Retrieval loss. It is the first work to constrain from the perspective of the ranking list in the VI-ReID, aligning with the goal of the testing stage. Moreover, to strengthen the robustness and cross-modality retrieval ability, we further introduce a Multi-Spectral Enhanced Ranking strategy for the testing phase. Based on the global feature only, our method outperforms existing methods by a large margin, achieving the remarkable rank-1 of 89.51% and mAP of 87.58% on the most challenging single-shot setting and all-search mode of the SYSU-MM01 dataset.