Patent ID: 6590972
Filing Date: 2003-07-08
Classification: H04Q

Abstract:
A system for determining DTMF tones, the system comprising:a linear predictive coding (LPC) analysis module, said LPC analysis module receiving an input signal, said input signal including a DTMF tone, said DTMF tone having a first frequency and a second frequency, said LPC analysis module computing LPC coefficients using said input signal; a cost-function generation module coupled to said LPC analysis module, said cost function generation module computing cost functions based at least in part upon said LPC coefficients; a predetermination module coupled to said cost function generation module, said predetermination module determining an initial first frequency and an initial second frequency by computing the values of said cost functions at a plurality of frequencies; and an enhancement module, said enhancement module being coupled to said predetermination module and said cost-function generation module, said enhancement module confirming that said initial first frequency is said first frequency and said initial second frequency is said second frequency based upon re-computing the values of said cost functions, said cost-functions being re-computed using said plurality of frequencies and using at least one adjustment factor.