Problem with Scaler II in polyphase 422 mode

Hi,

I have tried some more combinations and found that I can get it to work using a 4 or a 5 tap filter. In both of these cases I have used the Lanczos-2 function to generate the coefficients. It could be that I am generating the coefficients incorrectly for the 8/9 tap case. The Lanczos-2 function (f(x)) is defined over the interval [-2;2], but for the 9 tap coefficients, I need a function which is defined over [-4;4]. Should I stretch the Lanczos-2 function as follows: F'(x) = f(x/2)? According to the Altera documents, one should stretch it, but I have seen other documentation with coefficients for an 8-tap filter where the function is not stretched - it is simply used over the interval [-4; 4]. My DSP theory is severely rusted - otherwise I am sure the answer would have been obvious!

Regards,

Niki