topic Re:Polyphase Filter Length in Intel® Integrated Performance Primitives

Polyphase Filter Length

pq7 — Thu, 02 Sep 2021 03:18:41 GMT

In the example for ResamplePolyphaseGetFixedFilter

int inRate=16000; // input frequency int outRate=8000; // output frequency int history; // half of filter length char fname[]="filter.flt\0"; // coefficient file name { int size,len,height; FILE *file; short *pFilter; IppsresamplingPolyphaseFixed_16s *state; history=(int)(64.0f*0.5*IPP_MAX(1.0,1.0/(double)outRate/(double)inRate))+1; ...

What is the point of this expression on line 10? How does it ever result in anything other than 1.0?

IPP_MAX(1.0,1.0/(double)outRate/(double)inRate)

Since in C, x/y/z == x/(y*z)

Re:Polyphase Filter Length

ShivaniK_Intel — Thu, 02 Sep 2021 11:05:21 GMT

Hi,

Thanks for reaching out to us.

Thanks for bringing up this to our notice. We will get back to you soon.

Regards

Shivani

Re:Polyphase Filter Length

Ruqiu_C_Intel — Sat, 18 Sep 2021 09:49:49 GMT

Hi,

I am afraid not fully understood your question.

For the line 10 in the example, it calculates the filter length for fixed factor resampling. IPP developer reference guide mentioned that for general description of the polyphase resampling, please see "Multirate Digital Signal Processing" by R. Crochine and L. Rabier

Thanks

Re: Re:Polyphase Filter Length

pq7 — Tue, 21 Sep 2021 12:59:14 GMT

Thanks Ruqiu. Let me try to simplify the question for you:

Can you provide sample values for inRate and outRate such that the following expression does not give 1.0?

IPP_MAX(1.0,1.0/(double)outRate/(double)inRate)

Re: Re:Polyphase Filter Length

Andrey_B_Intel — Mon, 25 Oct 2021 15:07:03 GMT

I agree that result is 1.0 and this equation contains ambiguity.

The "outRate/inRate" ration in denominator more appropriate.

IPP_MAX(1.0, 1.0/( (double)outRate/(double)inRate) )

to increase filter length for decimation only.

Re:Polyphase Filter Length

Ruqiu_C_Intel — Mon, 15 Nov 2021 03:37:59 GMT

Thank you for teaching us. This issue is closing and we will no longer respond to this thread. If you require additional assistance from Intel, please start a new thread. Any further interaction in this thread will be considered community only.