Evolution of the ASR decoder design

Abstract

The ASR decoder is one of the fundamental components of an ASR system and has been evolving over the years to address the increasing demands for larger domains as well as the availability of more powerful hardware. Though the basic search algorithm (i.e. Viterbi search) is relatively simple, implementing a decoder which can handle hundreds of thousands of words in the active vocabulary and hundreds of millions of n-grams in the language model in real time is no simple task. With the emergence of embedded platforms, some of the design concepts used in the past to cope with limitations of the available hardware can become relevant again, where such limitations are similar to those of workstations of early days of ASR. In this paper we will describe various basic design concepts encountered in various decoder implementations, with the focus on those which are relevant today among the fairly large spectrum of available hardware platforms. © 2010 Springer-Verlag Berlin Heidelberg.