Diphone unit-selection system

The first feature we will examine is the base type, that is type of units we will use in the s5mthesiser. The base type chosen in second generation systems was often the diphone, as these often produced good joins. In unit selection, the increased variability in the units means that we can t always rely on diphones joining well, and so the reasons for using diphones are somewhat lessened. Indeed, from a survey of the literature, we see that almost every possible kind of base... 

Once we have found the units by our search, the actual S5mthesis process is often trivial. In pure unit selection, we have stored our units as waveforms, and so a simple overlap and add technique at the waveform boundaries is sufiicient. If we have stored the units in a more parametric representation (e.g. LP coefiicients and residuals), these can be S5mthesized in the same way as with second generation diphone synthesis. Some systems perform spectral smoothing between units, but again this can be performed with the same techniques as with second generation systems. 

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