Text-to-Speech Part II

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Text-to-SpeechPart II
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Previous Lecture Summary

• Previous lecture presented
• Text and Phonetic Analysis
• Prosody-I
• General Prosody
• Speaking Style
• Symbolic Prosody
• This lecture continues
• Prosody-II
• Duration Assignment
• Pitch Generation
• Prosody Markup Languages
• Prosody Evaluation

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Duration Assignment

• Pitch and duration are not entirely independent,
  and many of the higher-order semantic factors
  that determine pitch contours may also influence
  durational effects.
• Most systems often treat duration and pitch
  independently because of practical considerations
  van Santen. 1994.
• Numerous factors, including semantics and
  pragmatic conditions, might ultimately influence
  phoneme durations. Some factors that are
  typically neglected include
• The issue of speech rate relative to speaker
  intent, mood, and emotion.
• The use of duration and rhythm to possibly signal
  document structure above the level of phrase or
  sentence (e.g., paragraph).
• The lack of a consistent and coherent practical
  definition of the phone such that boundaries can
  be clearly located for measurement.

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Duration Assignment

• Rule-Based Methods
• Allen, 1987 identified a number of first-order
  perceptually significant effects that have
  largely been verified by subsequent research.

Perceptually significant effects for duration Allen, 1987.
Lengthening of the final vowel and following consonants in prepausal syllables.
Shortening of all syllabic segments (vowels and syllabic consonants) in nonprepausal position.
Shortening of syllabic segments if not in a word final syllable
Consonants in non-word-initial position are shortened.
Unstressed and secondary stressed phoned are shortened.
Emphasized vowels are lengthened.
Vowels may be shortened or lengthened according to phonetic features of their context.
Consonants may be shortened in clusters.
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Duration Assignment

• CART-based Durations
• A number of generic machine-learning methods have
  been applied to the duration assignment problem,
  including CART and linear regression Plumpe et
  al., 1998.
• Phone identity
• Primary lexical stress (binary feature)
• Left phone Context (1 phone)
• Right phone Context (1 phone)

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Pitch Generation

• Pitch, or F0, is probably the most characteristic
  of all the prosody dimensions.
• The quality of a prosody module is dominated by
  the quality of its pitch-generation component.
• Since generating pitch contours is an incredibly
  complicated problem, pitch generation is often
  divided into two levels, with the first level
  computing the so-called symbolic prosody and the
  second level generating pitch contours from this
  symbolic prosody.

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Pitch Generation

• Parametric F0 generation
• To realize all the prosodic effects, some systems
  make almost direct use of a real speaker