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An Overview of End-to-End Automatic Speech Recognition

by 1,2,*, 1,2,* and 1,2
1
Science and Technology on Parallel and Distributed Processing Laboratory, National University of Defense Technology, Changsha 410073, China
2
College of Computer, National University of Defense Technology, Changsha 410073, China
*
Authors to whom correspondence should be addressed.
Symmetry 2019, 11(8), 1018; https://doi.org/10.3390/sym11081018
Received: 30 June 2019 / Revised: 21 July 2019 / Accepted: 3 August 2019 / Published: 7 August 2019
Automatic speech recognition, especially large vocabulary continuous speech recognition, is an important issue in the field of machine learning. For a long time, the hidden Markov model (HMM)-Gaussian mixed model (GMM) has been the mainstream speech recognition framework. But recently, HMM-deep neural network (DNN) model and the end-to-end model using deep learning has achieved performance beyond HMM-GMM. Both using deep learning techniques, these two models have comparable performances. However, the HMM-DNN model itself is limited by various unfavorable factors such as data forced segmentation alignment, independent hypothesis, and multi-module individual training inherited from HMM, while the end-to-end model has a simplified model, joint training, direct output, no need to force data alignment and other advantages. Therefore, the end-to-end model is an important research direction of speech recognition. In this paper we review the development of end-to-end model. This paper first introduces the basic ideas, advantages and disadvantages of HMM-based model and end-to-end models, and points out that end-to-end model is the development direction of speech recognition. Then the article focuses on the principles, progress and research hotspots of three different end-to-end models, which are connectionist temporal classification (CTC)-based, recurrent neural network (RNN)-transducer and attention-based, and makes theoretically and experimentally detailed comparisons. Their respective advantages and disadvantages and the possible future development of the end-to-end model are finally pointed out. Automatic speech recognition is a pattern recognition task in the field of computer science, which is a subject area of Symmetry. View Full-Text
Keywords: automatic speech recognition; end-to-end; deep learning; neural network; CTC; RNN-transducer; attention; HMM automatic speech recognition; end-to-end; deep learning; neural network; CTC; RNN-transducer; attention; HMM
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Wang, D.; Wang, X.; Lv, S. An Overview of End-to-End Automatic Speech Recognition. Symmetry 2019, 11, 1018.

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