formant extraction using LPC

[raniaziedan]

hi every one
I am doing my PHD in accent recognition and I wanna to ask a question

when i have a wav sample for example 5 seconds
and i wanna to extract the formants using LPC

now i do LPC to whole signal then find the formants
[x, fs] = wavread('5sec.wav');
[a P] = lpc(x, ncoef); then find the formants

or apply LPC on each window seperately then find formants in each window , if this how i detect for example the first formant from all windows and how i detect the first formant from whole speech

thanks a lot