Post-lexical processing

Some systems use the output from the lexical lookup process and/or G2P conversion directly as the input to the synthesizer. In some systems, however, an additional step often known as post-lexical processing is performed, which modifies the output in some way. The most significant factor in determining how much post-lexical processing is performed is the specific form of the input to the synthesizer. This was discussed in Section 8.1.3, where we saw that we could choose high-level phonemic representation or a low-level detailed phonetic representation. A low-level representation will require significant processing, for example to turn an /n/ into an /m/ in a labial context, but, because 

Some processes operate at a purely phonological level, so, regardless of the type of input to the syntiiesizer, some processing may still be required. English doesn t really have any clear demonstrations of this, but when we consider French we see that the process of liaison must be modelled. In general, the word les is pronounced /I ey/, but, when followed by a word starting in a vowel, it is pronounced /I ey z/ as in les amis — /I ey z a m iy/. 

Some systems use the output fi om the lexical lookup process and/or grapheme-to-phoneme conversion directly as the input to the synthesizer. In some systems however, an additional step often known as post-lexical processing is performed which modifies the output in some way. The most significant factor in determining how much post lexical processing is the specific form of 

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First generation techniques usually require a quite detailed, low-level description of what is to be spoken. For purposes of explanation, we will take this to be a phonetic representation for the verbal component, along with a time for each phone, and an FO contour for the whole sentence. The phones will have been generated by a combination of lexical lookup, LTS rules and post-lexical processing (see Chapter 8), while the timing and FO contour will have been generated by a classical prosody algorithm of the type described in Chapter 9. It is often convenient to place this information in a new stmcture called a synthesis specification. Hence the specification is the input to the synthesiser and the waveform is the output. 

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