Results 1  10
of
22
Markovian Models for Sequential Data
, 1996
"... Hidden Markov Models (HMMs) are statistical models of sequential data that have been used successfully in many machine learning applications, especially for speech recognition. Furthermore, in the last few years, many new and promising probabilistic models related to HMMs have been proposed. We firs ..."
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Cited by 84 (2 self)
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Hidden Markov Models (HMMs) are statistical models of sequential data that have been used successfully in many machine learning applications, especially for speech recognition. Furthermore, in the last few years, many new and promising probabilistic models related to HMMs have been proposed. We first summarize the basics of HMMs, and then review several recent related learning algorithms and extensions of HMMs, including in particular hybrids of HMMs with artificial neural networks, InputOutput HMMs (which are conditional HMMs using neural networks to compute probabilities), weighted transducers, variablelength Markov models and Markov switching statespace models. Finally, we discuss some of the challenges of future research in this very active area. 1 Introduction Hidden Markov Models (HMMs) are statistical models of sequential data that have been used successfully in many applications in artificial intelligence, pattern recognition, speech recognition, and modeling of biological ...
Global Optimization of a Neural Network  Hidden Markov Model Hybrid
 IEEE Transactions on Neural Networks
, 1991
"... In this paper an original method for integrating Artificial Neural Networks (ANN) with Hidden Markov Models (HMM) is proposed. ANNs are suitable to perform phonetic classification, whereas HMMs have been proven successful at modeling the temporal structure of the speech signal. In the approach descr ..."
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Cited by 69 (16 self)
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In this paper an original method for integrating Artificial Neural Networks (ANN) with Hidden Markov Models (HMM) is proposed. ANNs are suitable to perform phonetic classification, whereas HMMs have been proven successful at modeling the temporal structure of the speech signal. In the approach described here, the ANN outputs constitute the sequence of observation vectors for the HMM. An algorithm is proposed for global optimization of all the parameters. Results on speakerindependent recognition experiments using this integrated ANNHMM system on the TIMIT continuous speech database are reported. 1 Introduction In spite of the fact that speech exhibits features that cannot be represented by a firstorder Markov model, Hidden Markov Models (HMMs) of speech units (e.g., phonemes) have been used with a good degree of success in Automatic Speech Recognition (ASR) (Rabiner & Levinson 85; Lee & Hon 89). Artificial Neural Networks (ANNs) have proven to be useful for classifying speech prop...
LeRec: A NN/HMM hybrid for online handwriting recognition
 Neural Computation
, 1995
"... We introduce a new approach for online recognition of handwritten words written in unconstrained mixed style. The preprocessor performs a wordlevel normalization by tting a model of the word structure using the EM algorithm. Words are then coded into low resolution \annotated images " where e ..."
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Cited by 43 (8 self)
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We introduce a new approach for online recognition of handwritten words written in unconstrained mixed style. The preprocessor performs a wordlevel normalization by tting a model of the word structure using the EM algorithm. Words are then coded into low resolution \annotated images " where each pixel contains information about trajectory direction and curvature. The recognizer is a convolution network which can be spatially replicated. From the network output, a hidden Markov model produces word scores. The entire system is globally trained to minimize wordlevel errors. 1
On adaptive decision rules and decision parameter adaptation for automatic speech recognition
 Proc. IEEE
, 2000
"... Recent advances in automatic speech recognition are accomplished by designing a plugin maximum a posteriori decision rule such that the forms of the acoustic and language model distributions are specified and the parameters of the assumed distributions are estimated from a collection of speech and ..."
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Cited by 27 (4 self)
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Recent advances in automatic speech recognition are accomplished by designing a plugin maximum a posteriori decision rule such that the forms of the acoustic and language model distributions are specified and the parameters of the assumed distributions are estimated from a collection of speech and language training corpora. Maximumlikelihood point estimation is by far the most prevailing training method. However, due to the problems of unknown speech distributions, sparse training data, high spectral and temporal variabilities in speech, and possible mismatch between training and testing conditions, a dynamic training strategy is needed. To cope with the changing speakers and speaking conditions in real operational conditions for highperformance speech recognition, such paradigms incorporate a small amount of speaker and environment specific adaptation data into the training process. Bayesian adaptive learning is an optimal way to combine
Discriminative speaker adaptation with conditional maximum likelihood linear regression
 In Eurospeech
, 2001
"... We present a simplified derivation of the extended BaumWelch procedure, which shows that it can be used for Maximum Mutual Information (MMI) of a large class of continuous emission density hidden Markov models (HMMs). We use the extended BaumWelch procedure for discriminative estimation of MLLRty ..."
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Cited by 25 (2 self)
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We present a simplified derivation of the extended BaumWelch procedure, which shows that it can be used for Maximum Mutual Information (MMI) of a large class of continuous emission density hidden Markov models (HMMs). We use the extended BaumWelch procedure for discriminative estimation of MLLRtype speaker adaptation transformations. The resulting adaptation procedure, termed Conditional Maximum Likelihood Linear Regression (CMLLR), is used successfully for supervised and unsupervised adaptation tasks on the Switchboard corpus, yielding an improvement over MLLR. The interaction of unsupervised CMLLR with segmental minimum Bayes risk lattice voting procedures is also explored, showing that the two procedures are complimentary. 1.
Large margin hidden markov models for speech recognition
, 2005
"... In this work, motivated by large margin classifiers in machine learning, we propose a novel method to estimate continuous density hidden Markov model (CDHMM) for speech recognition according to the principle of maximizing the minimum muticlass separation margin. The approach is named as large margi ..."
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Cited by 18 (2 self)
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In this work, motivated by large margin classifiers in machine learning, we propose a novel method to estimate continuous density hidden Markov model (CDHMM) for speech recognition according to the principle of maximizing the minimum muticlass separation margin. The approach is named as large margin HMM. Firstly, we show this type of large margin HMM estimation problem can be formulated as a constrained minimax optimization problem. Secondly, by imposing different constraints to the minimax problem, we propose three solutions to the large margin HMM estimation problem, namely the iterative localized optimization method, the constrained joint optimization method and the semidefinite programming (SDP) method. These new training methods are evaluated in the isolated Eset recognition task using ISOLET database and the TIDIGITS connected digit string recognition task. Experimental results clearly show that the large margin HMMs consistently outperform the conventional HMM training methods. It has been consistently observed that the large margin training method yields significant recognition error rate reduction even on top of some popular discriminative training methods.
Conditional random fields for integrating local discriminative classifiers
 Audio, Speech, and Language Processing, IEEE Transactions on
, 2008
"... Abstract—Conditional random fields (CRFs) are a statistical framework that has recently gained in popularity in both the automatic speech recognition (ASR) and natural language processing communities because of the different nature of assumptions that are made in predicting sequences of labels compa ..."
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Cited by 11 (2 self)
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Abstract—Conditional random fields (CRFs) are a statistical framework that has recently gained in popularity in both the automatic speech recognition (ASR) and natural language processing communities because of the different nature of assumptions that are made in predicting sequences of labels compared to the more traditional hidden Markov model (HMM). In the ASR community, CRFs have been employed in a method similar to that of HMMs, using the sufficient statistics of input data to compute the probability of label sequences given acoustic input. In this paper, we explore the application of CRFs to combine local posterior estimates provided by multilayer perceptrons (MLPs) corresponding to the framelevel prediction of phone classes and phonological attribute classes. We compare phonetic recognition using CRFs to an HMM system trained on the same input features and show that the monophone label CRF is able to achieve superior performance to a monophonebased HMM and performance comparable to a 16 Gaussian mixture triphonebased HMM; in both of these cases, the CRF obtains these results with far fewer free parameters. The CRF is also able to better combine these posterior estimators, achieving a substantial increase in performance over an HMMbased triphone system by mixing the two highly correlated sets of phone class and phonetic attribute class posteriors. Index Terms—Automatic speech recognition (ASR), random fields. I.
A Discriminative Training Algorithm for Hidden Markov Models
 IEEE TRANSACTIONS ON SPEECH AND AUDIO PROCESSING
, 2004
"... We introduce a discriminative training algorithm for the estimation of hidden Markov model (HMM) parameters. This algorithm is based on an approximation of the maximum mutual information (MMI) objective function and its maximization in a technique similar to the expectationmaximization (EM) algorit ..."
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Cited by 9 (0 self)
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We introduce a discriminative training algorithm for the estimation of hidden Markov model (HMM) parameters. This algorithm is based on an approximation of the maximum mutual information (MMI) objective function and its maximization in a technique similar to the expectationmaximization (EM) algorithm. The algorithm is implemented by a simple modification of the standard BaumWelch algorithm, and can be applied to speech recognition as well as to wordspotting systems. Three tasks were tested: Isolated digit recognition in a noisy environment, connected digit recognition in a noisy environment and wordspotting. In all tasks a significant improvement over maximum likelihood (ML) estimation was observed. We also compared the new algorithm to the commonly used extended BaumWelch MMI algorithm. In our tests the algorithm showed advantages in terms of both performance and computational complexity.
Hidden Neural Networks
 NEURAL COMPUTATION
, 1997
"... A general framework for hybrids of Hidden Markov models (HMMs) and neural networks (NNs) called Hidden Neural Networks (HNNs) is described. The paper begins by reviewing standard HMMs and estimation by conditional maximum likelihood, which is used by the HNN. In the HNN the usual HMM probability par ..."
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Cited by 7 (3 self)
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A general framework for hybrids of Hidden Markov models (HMMs) and neural networks (NNs) called Hidden Neural Networks (HNNs) is described. The paper begins by reviewing standard HMMs and estimation by conditional maximum likelihood, which is used by the HNN. In the HNN the usual HMM probability parameters are replaced by the outputs of state specific neural networks. As opposed to many other hybrids, the HNN is normalized globally and therefore has a valid probabilistic interpretation. All parameters in the HNN are estimated simultaneously according to the discriminative conditional maximum likelihood criterion. An evaluation of the HNN on the task of recognizing broad phoneme classes in the TIMIT database shows clear performance gains compared to standard HMMs tested on the same task.
An overview of discriminative training for speech recognition
"... This paper gives an overview of discriminative training as it pertains to the speech recognition problem. The basic theory of discriminative training will be discussed and an explanation of maximum mutual information (MMI) given. Common problems inherent to discriminative training will be explored a ..."
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Cited by 7 (0 self)
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This paper gives an overview of discriminative training as it pertains to the speech recognition problem. The basic theory of discriminative training will be discussed and an explanation of maximum mutual information (MMI) given. Common problems inherent to discriminative training will be explored as well as practicalities associated with implementing discriminative training for large vocabulary recognition. Alternatives to the MMI objective function such as minimum word error (MWE) and minimum phone error (MPE) will be discussed. The application of discriminative techniques for adaptation will be described. Finally, possible future avenues of research will be given. 1.