Online Discriminative Cross-Modal Hashing
X. Kang, Xingbo Liu, Xuening Zhang, Xiushan Nie, Yilong Yin
Abstract
Online cross-modal hashing has received increasing research attention due to its capability of encoding streaming data and updating hash functions simultaneously. Despite significant progress, there is still room for further improving accuracy from two aspects, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i.e</i> ., 1) enhancing discrimination of hash codes with an efficient training process; 2) elevating generalization performance by harmonizing the training and retrieval process. Inspired by this, we propose an Online Discriminative Cross-modal Hashing method, called ODCH. To enlarge the inter-class margin and magnify the intra-class similarity, ODCH skillfully constructs a discriminative semantic space and seamlessly integrates bit balance and uncorrelation constraints, discrete optimization, and asymmetric strategy for embedding the discriminative semantic information into hamming space. Furthermore, ODCH attempts to boost the generalization process by bridging the gap between learning and generalization. It develops adaptive bit-wise weights to reflect different learning conditions among bits and transmits them into the generalization process. Besides, the proposed discriminative embedding and adaptive weighting can be adopted by existing supervised cross-modal hashing methods, achieving more precise performance than the original versions. Extensive experiments on three benchmarked datasets show that ODCH achieves up to an average of 4.17% mAP score gains compared to state-of-the-art online cross-modal hashing methods, indicating its superiority.