Comparison of frame margin probability training to other discriminative methods for multi-condition speech recognition

English translation, also a kind of language conversion, refers to the activities of expressing each other in English to express another language or another language to express English. This paper aimed to evaluate and research methods of English translation based on the improved Gaussian mixture model (GMM). The paper proposed a simple evaluation and analysis of English translation using a discriminative training algorithm. In the experimental part, on the one hand, taking students, teachers, and translators as case study objects, through a questionnaire survey, it can be known that the number of students who scored more than 80 points in the English translation test is increasing every year, from 11.30% in the first year to 21.13% in the fourth year, an increase of nearly 10%. On the other hand, it can be seen from the speech translation experiment that the correct translation rate was 46.18% by using intelligent technology to distinguish translation. The experimental results showed that the discriminative training algorithm under the improved GMM algorithm is effective in the research of English translation evaluation.

In this work, we present a complete framework of discriminative training using non-uniform criteria for keyword spotting, adaptive boosted non-uniform minimum classification error (MCE) for keyword spotting on spontaneous speech. To further boost the spotting performance and tackle the potential issue of over-training in the non-uniform MCE proposed in our prior work, we make two improvements to the fundamental MCE optimization procedure. Furthermore, motivated by AdaBoost, we introduce an adaptive scheme to embed error cost functions together with model combinations during the decoding stage. The proposed framework is comprehensively validated on two challenging large-scale spontaneous conversational telephone speech (CTS) tasks in different languages (English and Mandarin) and the experimental results show it can achieve significant and consistent figure of merit (FOM) gains over both ML and discriminatively trained systems.

The minimum classification error (MCE) framework for discriminative training is a simple and general formalism for directly optimizing recognition accuracy in pattern recognition problems. The framework applies directly to the optimization of hidden Markov models (HMMs) used for speech recognition problems. However, few if any studies have reported results for the application of MCE training to large-vocabulary, continuous-speech recognition tasks. This article reports significant gains in recognition performance and model compactness as a result of discriminative training based on MCE training applied to HMMs, in the context of three challenging large-vocabulary (up to 100 k word) speech recognition tasks: the Corpus of Spontaneous Japanese lecture speech transcription task, a telephone-based name recognition task, and the MIT Jupiter telephone-based conversational weather information task. On these tasks, starting from maximum likelihood (ML) baselines, MCE training yielded relative reductions in word error ranging from 7% to 20%. Furthermore, this paper evaluates the use of different methods for optimizing the MCE criterion function, as well as the use of precomputed recognition lattices to speed up training. An overview of the MCE framework is given, with an emphasis on practical implementation issues

A smoothing method for minimum phone error linear regression (MPELR) is proposed in this paper. We show that the objective function for minimum phone error (MPE) can be combined with a prior mean distribution. When the prior mean distribution is based on maximum likelihood (ML) estimates, the proposed method is the same as the previous smoothing technique for MPELR. Instead of ML estimates, maximum a posteriori (MAP) parameter estimate is used to define the mode of prior mean distribution to improve the performance of MPELR. Experiments on a large vocabulary speech recognition task show that the proposed method can obtain 8.4% relative reduction in word error rate when the amount of data is limited, while retaining the same asymptotic performance as conventional MPELR. When compared with discriminative maximum a posteriori linear regression (DMAPLR), the proposed method shows improvement except for the case of limited adaptation data for supervised adaptation.

Improvement Comparison of Different Lattice-based Discriminative Training Methods in Chinese-monolingual and Chinese-English-bilingual Speech Recognition

In this paper we compare three frameworks for discriminative training of continuous-density hidden Markov models (CD-HMMs). Specifically, we compare two popular frameworks, based on conditional maximum likelihood (CML) and minimum classification error (MCE), to a new framework based on margin maximization. Unlike CML and MCE, our formulation of large margin training explicitly penalizes incorrect decodings by an amount proportional to the number of mislabeled hidden states. It also leads to a convex optimization over the parameter space of CD-HMMs, thus avoiding the problem of spurious local minima. We used discriminatively trained CD-HMMs from all three frameworks to build phonetic recognizers on the TIMIT speech corpus. The different recognizers employed exactly the same acoustic front end and hidden state space, thus enabling us to isolate the effect of different cost functions, parameterizations, and numerical optimizations. Experimentally, we find that our framework for large margin training yields significantly lower error rates than both CML and MCE training.

Minimum classification error (MCE) based discriminative methods have been extensively studied and successfully applied to automatic speech recognition, speaker recognition, and utterance verification. Our goal is to modify the embedded string model based MCE algorithm to handle the case of a large number of cross-syllable trip hones used in a large vocabulary recognition system. A selective strategy about MCE based discriminative training method, in particular for Mandarin speech syllable loop recognition, is introduced. We use a syllable loop recognition task to evaluate the performance of the acoustic model of an established large vocabulary continuous speech recognition system. The basic idea is that since decoding errors occur in parts of the models in whole decoded sentences, it is reasonable to adjust the parameters of the wrong models. As a result, a weighted MCE formulation is derived, which can provide more effective convergence and about a 10% error rate reduction for a large training set. Our experiments show that, although the performance of the recognition system is improved, some original correct recognition results are misrecognized after discriminative training, and a divide and conquer strategy is proposed as a solution. Thus, the acoustic feature space is divided into two or more sub-spaces according to the discriminative training procedure. By combining these two methods, we obtain over 14.5% error rate reduction in syllable loop recognition.

A novel algorithm for discriminative training of Choquet-integral-based fusion operators is described. Fusion is performed by Choquet integration of classifier outputs with respect to fuzzy measures. The fusion operators are determined by the parameters of fuzzy measures. These parameters are found by minimizing a minimum classification error (MCE) objective function. The minimization is performed with respect to a special class of measures, the Sugeno lambda-measures. An analytic expression is derived for the gradient of the Choquet integral with respect to the Sugeno lambda-measure. The new algorithm is applied to a landmine detection problem, and compared to previous techniques.

The authors developed a generalized probabilistic descent (GPD) method by extending the classical theory on adaptive training by Amari (1967). Their generalization makes it possible to treat dynamic patterns (of a variable duration or dimension) such as speech as well as static patterns (of a fixed duration or dimension), for pattern classification problems. The key ideas of GPD formulations include the embedding of time normalization and the incorporation of smooth classification error functions into the gradient search optimization objectives. As a result, a family of new discriminative training algorithms can be rigorously formulated for various kinds of classifier frameworks, including the popular dynamic time warping (DTW) and hidden Markov model (HMM). Experimental results are also provided to show the superiority of this new family of GPD-based, adaptive training algorithms for speech recognition. >

A statistically designed Automatic Speech Recognition (ASR) system extracts features from speech signals using feature extraction methods, links the extracted features with the expected phonetics of the hypothesis using acoustic models, uses language model to add prior information about the structure of the target language. For many years, Mel-frequency Cepstral coefficients (MFCC), n-gram, and Hidden Markov Model (HMM) approaches have been used predominantly for feature extraction, language modeling and acoustic modeling, respectively. However, performance degradation of MFCC in noisy conditions and inaccuracy of HMMs while handling large vocabularies have made researchers to propose more efficient methods. The proposed work uses noise robust method Gammatone Frequency Cepstral Coefficients(GFCC) for feature extraction, trigram language modeling, and HMM-Gaussian mixture model (GMM) based acoustic modeling to implement a continuous Hindi language ASR system. Also, it applies Differential Evolution (DE) technique to refine the GFCC features and discriminative techniques to enhance performance of the acoustic model. The performance of the implemented system has been evaluated by using different feature extraction methods, variants of n-gram language modeling techniques and different discriminative techniques in clean as well as noisy conditions. Initially, the results reveal that DE optimized GFCC with HMM-Gaussian Mixture Model (GMM) acoustic modeling performs better than MFCC, PLP and MF-PLP feature extraction methods. Secondly, the experimental results show that the Minimum Phone Error (MPE) outperforms Maximum Mutual Information (MMI) and Maximum Likelihood Estimation (MLE) and trigram based language modeling gives more accurate results than unigram and bigram language modeling. Finally, it has been concluded that the continuous Hindi language ASR system implemented using DE refined GFFC feature extraction method with MPE discriminative training technique and trigram based language modeling gives better accuracy in clean as-well-as noisy environments.

A critical component in the pattern matching approach to speech recognition is the training algorithm, which aims at producing typical (reference) patterns or models for accurate pattern comparison. In this paper, we discuss the issue of speech recognizer training from a broad perspective with root in the classical Bayes decision theory. We differentiate the method of classifier design by way of distribution estimation and the discriminative method of minimizing classification error rate based on the fact that in many realistic applications, such as speech recognition, the real signal distribution form is rarely known precisely. We argue that traditional methods relying on distribution estimation are suboptimal when the assumed distribution form is not the true one, and that optimality in distribution estimation does not automatically translate into optimality in classifier design. We compare the two different methods in the context of hidden Markov modeling for speech recognition. We show the superiority of the minimum classification error (MCE) method over the distribution estimation method by providing the results of several key speech recognition experiments. In general, the MCE method provides a significant reduction of recognition error rate.

Discriminative training aims at constructing a classifier that is of small scale but has high classification power. One type, Minimum Classification Error (MCE) training, has been used widely in pattern recognition, especially in the speech recognition field. In parallel with this, Relevance Vector Machine (RVM) has attracted many researchers' interest, based on its potential for alleviating the scalability problem of Support Vector Machine (SVM). It has been reported that RVM achieves high classification accuracy with a limited amount of classifier parameters, i.e., relevance vectors. Comparison studies between MCE training and SVM have been done, but not so much between MCE training and RVM. Motivated by this, we conduct theoretical and experimental comparisons of MCE training and RVM. Results show that MCE training is better suited to the development of small-scale but highly discriminative classifiers than its counterpart.

A derivation of minimum classification error from the theoretical classification risk using Parzen estimation

In this paper, we present the theoretical framework of minimum classification error (MCE) training of generalized linear classifiers for text classification. We show that many important text classifiers, either probabilistic or non-probabilistic, can be unified under this framework, and the proposed MCE classifier training approach can be applied to improve the classifier performance. In addition, we describe an effective MCE classifier training algorithm that uses AdaBoost to generate alternative initial classifiers, as opposed to combining multiple classifiers as it is typically used. This method is applied to MCE classifier training to overcome local minimums in optimal classifier parameter search, utilizing the fact that the family of generalized linear classifiers is closed under AdaBoost. Moreover, we extend the loss function in MCE training to incorporate training sample prior distributions to compensate the imbalanced training data distribution in each category. Experimental studies are performed on the text classification tasks, and the significant classification error reductions of 25% - 55% are observed.

A comparative study of RPCL and MCE based discriminative training methods for LVCSR