Speech driven lip synthesis is an interesting and important step toward human-computer interaction. An incoming speech signal is time aligned using a speech recognizer to generate phonetic sequence which is then converted to corresponding viseme sequence to be animated. In this paper, we present a novel method for generation of the viseme sequence, which uses viseme based acoustic models, instead of usual phone based acoustic models, to align the input speech signal. This results in higher accuracy and speed of the alignment procedure and allows a much simpler implementation of the speech driven lip synthesis system as it completely obviates the requirement of acoustic unit to visual unit conversion. We show through various experiments that the proposed method results in about 53% relative improvement in classification accuracy and about 52% reduction in time, required to compute alignments.
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