Semantic Bilinear Pooling for Fine-Grained Recognition

Fine-grained recognition, e.g., vehicle identification or bird classification, naturally has specific hierarchical labels, where fine levels are always much harder to be classified than coarse levels. However, most of the recent deep learning based methods neglect the semantic structure of fine-grained objects, and do not take advantages of the traditional fine-grained recognition techniques (e.g. coarse-to-fine classification). In this paper, we propose a novel framework, i.e., semantic bilinear pooling, for fine-grained recognition with hierarchical multi-label learning. This framework can adaptively learn the semantic information from the hierarchical labels. Specifically, a generalized softmax loss is designed for the training of the proposed framework, in order to fully exploit the semantic priors via considering the relevance between adjacent levels. A variety of experiments on several public datasets show that our proposed method has very impressive performance with low feature dimensions compared to other state-of-the-art methods.