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Introduction of Grphones. Dong Wang 05/05/2008. Content. Grphones Graphone-based LVCSR Graphone-based STD. Graphones. Suppose graphemes and phonemes are two streams from a single stochastic process. Example speaking s p ea k i ng [spi:king] [s] [p] [i:] [k] [i] [ng].

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introduction of grphones

Introduction of Grphones

Dong Wang

05/05/2008

content
Content
  • Grphones
  • Graphone-based LVCSR
  • Graphone-based STD
graphones
Graphones
  • Suppose graphemes and phonemes are two streams from a single stochastic process
  • Example

speaking s p ea k i ng

[spi:king] [s] [p] [i:] [k] [i] [ng]

graphones1
Graphones
  • The grapheme-phoneme join units are called graphones.
  • Suppose no context dependence among graphones, leading to simplest graphone model. With a known alignement L, the join probability can be written:
  • The whole work is to define u and estimate p(u)
graphones2
Graphones
  • If the graphon model is ready, we can estimate the phoneme sequence from a grapheme sequence, and vice versa.

Deligne, Sabine / Yvon, Francois / Bimbot, Frédéric (1995): "Variable-length sequence matching for phonetic transcription using joint multigrams", In EUROSPEECH-1995, 2243-22

graphones3
Graphones
  • As the alignment is unkown in the training corpus (dictionary), an EM procedure can be used, with the alignment as latent variable.

Z

E

E

E

E

P

z

i

p

graphones4
Graphones
  • Iterative process is as the following, where c is the counts of occurrence:
  • A forward-back process is used to avoid redundant computation
graphones5
Graphones
  • Some tricks
    • Null grapheme or phoneme segment is allowed, however null-null graphones are not allowed
    • Mutual information could be used to estimate the model accuracy among different length variables
    • In English, I used gg length from 0-3, while pp length from 0-1.
graphones6
Graphones
  • Some experiments
      • Mutual information:

gr(0-3)ph(0-1): 0.86 gr(0-1)ph(0-1): 0.58

      • High-probable graphones

A+ax 7.587430e-01

E+iy 6.197528e-02

I+ay 4.753983e-02

O+ow 4.640152e-02

A+ 1.886822e-02

+ax 1.882734e-02

VE+v 1.074523e-02

ER+er 8.942506e-03

LL+l 8.298488e-03

CH+ch 5.454664e-03

SS+s 2.709674e-03

graphone based lvcsr
Graphone-based LVCSR
  • M. Bisani, H. Ney , Multigram-based Grapheme-to-Phoneme Conversion for LVCSR , In Proc. Eurospeech, Geneva, Switzerland, 2003

Transcribe lexicon for new words using graphone models

graphone based std
Graphone-based STD
  • Using multi-gram model to generate graphone forms for out-of-vocabulary words.
  • Train hybrid language models which contains both in-vocabulary words and graphones.
  • Decoding using the lexicon expanded with graphones.
  • Searching INV words as in word lattices, and OOV words as in phoneme lattices.

Murat Akbacak, Dimitra Vergyri, Andreas Stolcke ,OPEN-VOCABULARY SPOKEN TERM DETECTION USING GRAPHONE-BASED HYBRID RECOGNITION SYSTEMS , ICASSP08, Los Angels, USA.

graphone based std1
Graphone-based STD
  • Only the hybrid system can detect OOV words
  • For INV words, the hybrid system works better also.

Murat Akbacak, Dimitra Vergyri, Andreas Stolcke ,OPEN-VOCABULARY SPOKEN TERM DETECTION USING GRAPHONE-BASED HYBRID RECOGNITION SYSTEMS , ICASSP08, Los Angels, USA.

graphone based std2
Graphone-based STD
  • What is the difference between grahpone and phoneme based STD, considering OOV?
  • How if we use decision trees to perform the LTS?
  • How if we train the multi-gram using the whole text corpus, instead of the dictionary, hence including the frequency information?
conclusions
Conclusions
  • Graphone model is an alternative for decision trees to performance LTS.
  • Graphone models can be used to detect multi-letter graphemes
  • Word-subword hybrid system seems interesting.