A Framework for Classifier Adaptation for Large-Scale Multimedia Data

Machine learning techniques have been used extensively to build models for the analysis and retrieval of multimedia data. The explosion of multimedia data on the Web poses a great challenge to such techniques not simply because of the sheer data volume, but also because of the heterogeneity of the data. With data from a wide variety of domains, models trained from one domain do not generalize well to other domains, while at the same time it is prohibitively expensive to build new models for each and every domain due to the high cost for labeling training examples. In this paper, we tackle the heterogeneity challenge in large-scale multimedia data using cross-domain model adaptation for better performance and reduced human cost. Specifically, we investigate the problem of adapting supervised classifiers trained from one or more source domains to a new classifier for a target domain that has only limited labeled examples. The foundation of our work is a general framework for function-level classifier adaptation based on the regularized loss minimization principle, which adapts a classifier by directly modifying its decision function. Under this framework, one can derive concrete adaptation algorithms by plugging in any loss and regularization functions, among which we elaborate on adaptive support vector machines (a-SVM). We further extend this framework for multiclassifier adaptation, namely adapting multiple existing classifiers into a classifier for the target domain, in a way that the contributions of these existing classifiers are automatically determined. We evaluate the proposed approaches in cross-domain semantic concept detection based on TRECVID corpora. The results show that our approaches outperform existing (adaptation and nonadaptation) methods in terms of accuracy and/or efficiency, and adaptation from multiple classifiers offers further benefits.