Prominence prediction prosody

Informally we can describe prosody as the part of human communication which expresses emotion, emphasises words, shows speaker attitude, breaks a sentence into phrases, governs sentence rhythm and controls the intonation, pitch or tune of the utterance. This chapter describes how to predict prosodic form from the text while Chapter 9 goes on to describe how to synthesize the acoustics of prosodic from these form representations. In this chapter we first we introduce the various manifestations of prosody in terms of phrasing, prominence and intonation. Next we go on to describe how prosody is used in communication, and in particular explain why this has a much more direct affect on the final speech patterns than with verbal communication. Finally we describe techniques for predicting what prosody should be generated from a text input. 

A completely comprehensive approach to timing would therefore attempt to model all these factors, but in general it is very hard to determine any reliable anchor points at a level lower than the phone. In practical TTS, the complex sub-phone timing patterns are often ignored as firstly it is difficult to predict the interactions and secondly it is subsequently difficult to know what to do with the sub-phone information once obtained. In practice then the most common approaches are to predict syllable durations or phone durations. Syllables are attractive as they seem to be the natural units of prosody we have seen elsewhere that they are the units of prominence and therefore pitch accent placement. In addition, we usually think of the syllable as being the natural unit of rhythm. Phones are attractive as they are the smallest units we can predict and therefore allow the most detail in prediction. 

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