Fine-Grained Fragment Diffusion for Cross Domain Crowd Counting

Deep learning improves the performance of crowd counting, but model migration remains a tricky challenge. Due to the reliance on training data and inherent domain shift, model application to unseen scenarios is tough. To facilitate the problem, this paper proposes a cross-domain Fine-Grained Fragment Diffusion model (FGFD) that explores feature-level fine-grained similarities of crowd distributions between different fragments to bridge the cross-domain gap (content-level coarse-grained dissimilarities). Specifically, we obtain features of fragments in both source and target domains, and then perform the alignment of the crowd distribution across different domains. With the assistance of the diffusion of crowd distribution, it is able to label unseen domain fragments and make source domain close to target domain, which is fed back to the model to reduce the domain discrepancy. By monitoring the distribution alignment, the distribution perception model is updated, then the performance of distribution alignment is improved. During the model inference, the gap between different domains is gradually alleviated. Multiple sets of migration experiments show that the proposed method achieves competitive results with other state-of-the-art domain-transfer methods.