LATTICE GENERATION

A lattice or word graph is a point-to-point description of the search through the language model as indicated in the figure below.




• The generated lattice can be applied in a second pass decoding to constrain the search space, and can be reused to efficiently test new acoustic models or language models.

• Modifications to the ISIP decoder:

  
  

  • Add a new level path marker object (trace) - word level. So now the ISIP decoder explicitly maintains three-level traces - state, phone and word level.

  
  

  • Allow each path marker object to maintain a list of backpointers instead of a single backpointer. The size of the list at each level is specified by the user.

  
  

  • At the search end, recursively backward traverse along the backpointers and construct the lattice, then write this lattice into a file, which can be used in the second pass decoding.