Re: DFT or DFS: Are they the same thing?

On Aug 9, 9:14 am, robert bristow-johnson <r...@xxxxxxxxxxxxxxxxxxxx>
wrote:
On Aug 9, 10:52 am, dbd <d...@xxxxxxxx> wrote:
...

what is the non-zero length of your FIR and what is N, the DFT size?
and how many uncorrupted output samples do you expect to get for each
frame?

r b-j

N is the DFT size.

N-1
X[n] = (1/N) SUM{ x[k] e^(-j*2*pi*n*k/N) }
k=0

The complex exponentials are the FIR filter coefficients. The DFT
formula, for each n, is a linear time domain convolution. I get one
sample, X[n], for the n-th filter of the N filters in the filter bank,
X, for each time I call the N point DFT.

When the complex exponential FIR filter coefficients embedded in the
DFT definition are suitable for my FIR applications, I can achieve
better computational efficiency by calculating my FIR filter bank by
calling the FFT. Fortunately, many applications find the complex
exponential FIR coefficients useful enough to benefit from this
computational advantage.

Dale B. Dalrymple

.

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