SSML Extensions for TTS in Indian Languages II workshop on Internationalizing SSML 30-31 May 2006, Greece

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SSML Extensions for TTS in Indian LanguagesII
workshop on Internationalizing SSML 30-31 May
2006, Greece

• Nixon Patel and Kishore Prahallad
• Bhrigus Inc. Hyderabad, India
• IIIT Hyderabad, India

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Topics

• About Bhrigus
• Collaborative Efforts between Bhrigus and IIIT
  Hyderabad
• Nature of Indian language scripts convergence
  and divergence
• Issues across TTS rendering in all these
  languages
• Proposed solutions/tags
• Syllable Element
• Alien Element
• Dialect Element

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Bhrigus voice data solutions
http//www.bhrigus.com
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About Bhrigus

• Established 2002
• Business Providing IVR, Speech
  
• 
  Enterprise solutions to BFSI,
• 
  Telcos, contact centers
• 
  manufacturing companies.
• Key Customers Hewitt Associates,
• ATT,
  Pfizer, Merrill Lynch,
• Union
  pacific railroad, CDIA,
• South
  western energy,
• Orange
  county, Stryker
• SEI CMM Level 4 Process Implementation
  undergoing, ISO 9001 2000 KPMG certified.

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Speech and Language Technology Lab _at_ Bhrigus

• Playing a leadership role in the development of
  ASR and TTS for all official Indian languages to
  provide voice solutions for Indian market
• Collaborations IIIT Hyderabad, Carnegie Mellon
  University
• 10 member team board of advisors
• 3 PhDs and 4 Masters
• Synthesis team, Recognition team, Linguist team
  and Language resources team
• Initiating SSML and VXML chapters in India

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Collaborative Efforts

• Bhrigus Inc. Hyderabad Voice based solution
  providers
• IIIT Hyderabad one of the leading universities
  in India doing speech research
• Telugu TTS Collaborative Efforts between
  Bhrigus Inc. and IIIT
• Goal Develop ASR and TTS for all official Indian
  languages

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Nature of Indian Language (IL) Scripts

• Basic units of the writing system are Aksharas
• An Akshara is an orthographic representation of a
  speech sound
• Akshara is syllabic in nature, typical forms are
  V, CV, CCV and CCCV (C consonant, V vowel)
• Always ends with a vowel (or nasalized vowel) in
  written form
• 1652 dialects/native languages
• 22 languages officially recognized

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Convergence of IL Scripts

• Aksharas are syllabic in nature
• Common phonetic base
• Share a common set of speech sounds across all
  languages
• Fairly good (though not exact) correspondence
  between sequence of Aksharas and the
  corresponding sequence of sounds
• Often referred to as Letter-to-sound rules
• Written from left-to-right as in European
  languages
• Words are separated by space as in European
  languages

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Divergence of IL Scripts

• Each IL has its own script
• All IL share a common phonetic base however,
  Phonotactics in each IL are different from each
  other
• IL are non-tonal languages unlike eastern
  languages such as Chinese

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How to represent Indian language Scripts

• Unicode
• Useful for rendering the Indian language
  scripts
• Not suitable for keying-in through QWERTY key
  board
• Not suitable to build modules such as
  text-normalization (cant see the Unicode
  characters on many editors)
• Itrans-3 / OM - A transliteration scheme by IISc
  Bangalore, India and Carnegie Mellon University
• Useful for keying-in and store the scripts of
  Indian language using QWERTY keyboards
• Useful for processing and writing modules/rules
  for letter-to-sound, text normalization etc.

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Itrans-3 / OM Notation
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Why Itrans-3/OM?

• Developed from the user readability aspects
  Easier to read and type
• It is case-insensitive.
• This scheme is phonetic in nature, the characters
  corresponds to the actual sound that is being
  spoken.
• Thus a single transliteration scheme is used for
  all the Indian languages, as they share the same
  set of sounds.
• Each character (corresponding to a phone/sound)
  is not more than three letters length.
• Adapted across Universities in India/Abroad and
  some industrial labs such as Bhrigus Inc.

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Issues in TTS rendering in IL

• TTS should be able to pronounce words as Akshara
  (syllable) by Akshara (syllable)
• Languages have heavy influence of English (alien)
  words
• Alien words occur in between the sentences
• Each language has its own dialect

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SSML Tag Phoneme Element ltphonemegt

• ltphoneme alphabet"itrans-3" ph"n aa t oo"gt
  naatoo lt/phonemegt
• Ph attribute specifies phoneme/phone string
• Rendering n aa t oo individually does not
  make sense to the native speakers of Indian
  languages
• Sounds needs to be rendered in terms of syllables

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Syllable Element ltsyllablegt

• ltsyllable alphabet"itrans-3" syl"naa too"gt
  naatoo lt/syallablegt
• Render naa and too which are Aksharas
  (syllables)

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Motivation for Loan Word ltaliengt

• Informal experiments suggested 33 of errors of
  TTS of IL occur while rendering alien
  (non-native) words
• Such alien words could be automatically detected
  due to syllabic properties of the Indian
  languages

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Example of loan word

• BANK has to be pronounce as /B/ /AE/ /N/ /K/
• /AE/ phoneme does not exist in Indian language
  phone set
• ltaliengt baank lt/aliengt
• Alien (non-native) words could be rendered using
  different pronunciation dictionaries or
  letter-to-sound rules

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Dialect Element ltdialectgt

• Each language has its own dialect
• TTS should be able to handle dialects without
  unloading the language resources

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Dialect Element ltdialectgt

• lt?xml version"1.0"?gtltspeak version"1.0"
  xmllang"tel-in"gt
• ltvoice gender"female"gt
• ltdialect name andhragt yekkadiki vellaali
  lt/dialectgt
• ltdialect name telengana pro yaadiki
  poovaalegt yekkadiki vellaali lt/dialectgt
• lt/voicegtlt/speakgt

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Conclusions

• Bhrigus Inc. Hyderabad taking lead position to
  develop ASR and TTS for Indian languages
• Proposed ltsyllablegt ltaliengt ltdialectgt elements
  for SSML extensions

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References

• Prahallad Lavanya, Prahallad Kishore and
  GanapathiRaju Madhavi, A Simple Approach for
  Building Transliteration Editors for Indian
  Languages, Journal of Zhejiang University
  Science, vol.6A, no.11, pp. 1354-1361, Oct 2005.