Chien Jen-Tzung, Liao Chih-Pin
Departmernt of Computer Science and Information Engineering, National Cheng Kung University, Tainan, Taiwan.
IEEE Trans Pattern Anal Mach Intell. 2008 Apr;30(4):606-16. doi: 10.1109/TPAMI.2007.70715.
This paper presents a hybrid framework of feature extraction and hidden Markov modeling(HMM) for two-dimensional pattern recognition. Importantly, we explore a new discriminative training criterion to assure model compactness and discriminability. This criterion is derived from hypothesis test theory via maximizing the confidence of accepting the hypothesis that observations are from target HMM states rather than competing HMM states. Accordingly, we develop the maximum confidence hidden Markov modeling (MC-HMM) for face recognition. Under this framework, we merge a transformation matrix to extract discriminative facial features. The closed-form solutions to continuous-density HMM parameters are formulated. Attractively, the hybrid MC-HMM parameters are estimated under the same criterion and converged through the expectation-maximization procedure. From the experiments on FERET and GTFD facial databases, we find that the proposed method obtains robust segmentation in presence of different facial expressions, orientations, etc. In comparison with maximum likelihood and minimum classification error HMMs, the proposed MC-HMM achieves higher recognition accuracies with lower feature dimensions.
本文提出了一种用于二维模式识别的特征提取与隐马尔可夫模型(HMM)的混合框架。重要的是,我们探索了一种新的判别训练准则,以确保模型的紧凑性和可区分性。该准则通过最大化接受观测来自目标HMM状态而非竞争HMM状态这一假设的置信度,从假设检验理论推导而来。相应地,我们开发了用于人脸识别的最大置信隐马尔可夫模型(MC-HMM)。在此框架下,我们合并一个变换矩阵来提取有区分性的面部特征。给出了连续密度HMM参数的闭式解。吸引人的是,混合MC-HMM参数在相同准则下进行估计,并通过期望最大化过程收敛。从在FERET和GTFD面部数据库上的实验中,我们发现所提出的方法在存在不同面部表情、方向等情况下能获得稳健的分割。与最大似然和最小分类误差HMM相比,所提出的MC-HMM在较低特征维度下实现了更高的识别准确率。