Discrete online cross-modal hashing

Abstract

With the prevalence of multimedia content on the Web which usually continuously comes in a stream fashion, online cross-modal hashing methods have attracted extensive interest in recent years. However, most online hashing methods adopt a relaxation strategy or real-valued auxiliary variable strategy to avoid complex optimization of hash codes, leading to large quantization errors. In this paper, based on Discrete Latent Factor model-based cross-modal Hashing (DLFH), we propose a novel cross-modal online hashing method, i.e., Discrete Online Cross-modal Hashing (DOCH). To generate uniform high-quality hash codes of different modal, DOCH not only directly exploits the similarity between newly coming data and old existing data in the Hamming space, but also utilizes the fine-grained semantic information by label embedding. Moreover, DOCH can discretely learn hash codes by an efficient optimization algorithm. Extensive experiments conducted on two real-world datasets demonstrate the superiority of DOCH.