Patent ID: 7634407

Claim:
A method of indexing a speech segment, the method comprising: identifying a lattice of speech unit sequences by performing speech recognition on the speech segment, the lattice comprising states with transitions between states, each transition representing a speech unit and all transitions into a state representing the same speech unit; for each transition into each state, determining all possible speech unit positions that the speech unit for the transition occupies in all speech unit sequences that pass through the transition; for each state in the lattice, defining at least one sub-state with a separate sub-state for each different speech unit position determined from all of the transitions into the state such that sub-states for two different states represent a same speech unit at a same speech unit position; calculating a position score for each sub-state; summing the position scores of sub-states for different states, where the sub-states represent the same speech unit at the same speech unit position, to form a posterior probability for the speech unit in the speech unit position; for each speech unit in the lattice of speech unit sequences, placing information in an entry in the index that indicates a speech unit position of the speech unit in at least one speech unit sequence and the posterior probability of the speech unit in the speech unit position.