Inter-frame dependence arising from preceding and succeeding frames - Application to speech recognition

This paper extends the notion of capturing temporal information within an H MM framework by permitting the observed frame not only to be dependent upon preceding frames, but also upon succeeding frames. In particular the IFD-H MM (Ming and Smith, 1996) is extended to support any number of preceding an d/or succeeding frame dependencies. The means through which such a dependen cy might be integrated into an HMM framework are explored, and details give n of the resultant changes to the IFD-HMM. Experimental results are provide d, contrasting the use of bi-directional frame dependencies to the use of p receding only frame dependencies and exploring how such dependencies can be best employed. It was found that a dependency upon succeeding frames enabl ed dynamic spectral information not found in the preceding frames to be use fully employed, resulting in a significant increase in the recognition accu racy. It was also found that the use of frame dependencies proved to be a m ore effective means of increasing recognition accuracy than the use of mult iple mixtures. (C) 1999 Elsevier Science B.V. All rights reserved.