Lattice generation with accurate word boundary in WFST framework

This paper presents an algorithm to generate the speech recognition lattice with accurate word boundary in weighted finite-state transducer (WFST) decoding framework. In traditional WFST lattice generation algorithms, the transformation from context-dependent phone lattice to word lattice does not yield accurate time boundaries between words. Meanwhile, this lattice is not a Standard Lattice Format nor is it compatible with existing toolkits. The lattice without word boundary can only be used in the area where the word boundary is not needed. In this paper, we propose a lexicon matching algorithm based on token passing to transform the phone lattice to the word lattice. This algorithm generates standard lattices with accurate word boundary. The experiments show that the proposed lattice generation algorithm has an good lattice quality and good algorithm efficiency.