IIR filter diverges

[srodriguez]

Hi,
I am using IPP 5.1. I am trying to implement an IIR, Butterworth with cutoff at 100Hz. I have obtained the coefficients from Matlab and and tried the filter there; I also tried the same coefficients in Scilab and also the filter worked pretty well.
When I try to use those coefficients with IPP and this function ippsIIR_32f, the filter diverges, I beleive I have callled all initialization and allocation methods before calling ippsIIR_32f...... Has anybody have gotten good success with an IIR from IPP ?
Did you have to do any special arrangements onthe coefficient ordering that is not standard?
Thank you.
God bless you

[Vladimir_Dudnik]

Hello,

please see answer from our expert

/* =======================================
Order of taps = b0,b1,...,bN,a0,a1,...,aN
N = order
======================================== */
It is mentioned in the manual. Also Butterworth coefficients generation is
available in ipp52 (the only difference with Matlab is that input cutoff freq
should be 1/2F from used in MatLab (it is also described in the manual).

Regards,
Vladimir