A two-channel training algorithm for hidden Markov model and its application to lip reading

  • Authors:
  • Liang Dong;Say Wei Foo;Yong Lian

  • Affiliations:
  • Department of Electrical and Computer Engineering, National University of Singapore, Singapore;School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore;Department of Electrical and Computer Engineering, National University of Singapore, Singapore

  • Venue:
  • EURASIP Journal on Applied Signal Processing
  • Year:
  • 2005

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Abstract

Hidden Markov model (HMM) has been a popular mathematical approach for sequence classification such as speech recognition since 1980s. In this paper, a novel two-channel training strategy is proposed for discriminative training of HMM. For the proposed training strategy, a novel separable-distance function that measures the difference between a pair of training samples is adopted as the criterion function. The symbol emission matrix of an HMM is split into two channels: a static channel to maintain the validity of the HMM and a dynamic channel that is modified to maximize the separable distance. The parameters of the two-channel HMM are estimated by iterative application of expectation-maximization (EM) operations. As an example of the application of the novel approach, a hierarchical speaker-dependent visual speech recognition system is trained using the two-channel HMMs. Results of experiments on identifying a group of confusable visemes indicate that the proposed approach is able to increase the recognition accuracy by an average of 20% compared with the conventional HMMs that are trained with the Baum-Welch estimation.