On the use of a hybrid harmonic/stochastic model for TTS synthesis-by-concatenation

Abstract In this paper, we address the possibilities offered by hybrid harmonic/stochastic (H/S) models in the context of wide-band text-to-speech synthesis based on segment concatenation. After a brief recall of the hypotheses underlying such models and a comprehensive review of a well-known analysis algorithm, namely the one provided by the multi-band excited (MBE) analysis framework, we study how H/S models allow to modify the prosody of segments and how segment concatenation can be organized, in the purpose of minimizing mismatches at the border of segments. In this context, we introduce an original concatenation algorithm which takes advantage of some analysis errors. Speech synthesis algorithms are then described, including an original synthesis technique based on judiciously prepared IFFTs, and the final segmental quality 1 is detailed. More particularly, we examine the differences in the quality obtained when using the model in a narrow-band speech coding context and in a wide-band, concatenation based synthesis context. We study three possible causes for these differences: the choice of an analysis criterion, the inadequacy of the model due to pitch variatons, and the effect of coarticulation on phases.