Method and apparatus to modify pitch estimation function in acoustic signal musical note pitch extraction

A computer-readable storage medium storing a computer program for causing the computer to estimate pitch in an acoustic signal by operations of:

• initializing a function ƒt and a time t, where t=0, x′0=ƒ0(F0), x′0 is a pitch estimate at time zero and F0 is a frequency of the acoustic signal at time zero;
• determining at least one pitch estimate using the function x′t=ƒt(Ft) by an iterative process of creating ƒt+1(Ft+1) based at least partly on pitch estimates x′t, x′t−1, xt−2, xt−3, . . . , and functions ƒt(Ft), ƒt−1(Ft−1), ƒt−2(Ft−2), ƒt−3(Ft−3) . . . and incrementing t;
• and calculating at least one final pitch estimate.

A system comprising means for receiving data representing an acoustic signal and processing means to process the received data to estimate a pitch of the acoustic signal, where said processing means comprises means for initializing a function ƒt, and a time t, where t=0, x′0=ƒ0(F0), x′0 is a pitch estimate at time zero and F0 is a frequency of the acoustic signal at time zero;

• means for determining at least one pitch estimate using the function x′t=ƒt(F0) by an iterative process of creating ƒt+1(Ft+1) based at least partly on pitch estimates x′t, x′t−1, x′t−2, x′t−3, . . . , and functions ƒt(Ft), ƒt−1(Ft−1), ƒt−2(Ft−2), ƒt−3(Ft−3) . . . and incrementing t;
• and means for determining at least one final pitch estimate (xt).