cascade filtering usign FFT (sherin tech )

Subject: cascade filtering usign FFT
From:    sherin tech  <sherin.tech@xxxxxxxx>
Date:    Fri, 7 Apr 2006 18:26:46 +0530

Hi,

I had posted some queries on filtering using FFT (in frequency domain).
I could implement it properly.

my working code is doing ...

// doing one filtering

ie,           input -> Filter_1 -> output

while(1)
{
1) Take 512 samples input (no windowing, so, hop size is 512 again).
    Zero pad it to make it 1024.
    Take 1024 point FFT.
2) Take 128 filter-1 coeff ,
    zero pad to make it 1024.
   Take 1024 FFT.
3) Multiply the spectrum to get 1024 bins.
4) Take 1024 point IFFT.
5) do a 50 % overlap and add to get back 512 out sample..
}

Now, I want to do the 2nd filtering in a cascaded manner ..
ie,
          input -> Filter_1 -> Filter_2 -> output


what is the best way to do this ??

coming back to time domain and going for another filtering using FFT
won't be efficient .. i guess .

conceptually multiplying the Transfer function of these two filters
will give the resultant Transfer function...

whats the practical approach ?

need


regards,
sherin