Hi Heavyfranz,
All you need to do is to apply a window function to each
batch of 4096 samples. Don't use a triangular window though;
its only advantage is that it is marginally easier to
calculate a triangular function.
You mention "overlap add." this technique would be used
only if you were intending to implement a filter function
in addition to the spectrum analysis you mention. In that
case, if you are filtering using FFT-based convolution, it
is essential that you do not window the data because
windowing would cause severe modulation in the resulting
time-domain output of the filter.
Regards,
John
On 27/10/2011 1:50 AM, heavyfranz wrote:
> Hi, I'm doing a spectrum analyzer. i collect 4096 samples of data from
> codec then I stop interrupt and begin fft.
> The algoritm that I use ( in the ti's dsplib) does not provide a windowing,
> so I don't understand if would be ok to do some "by-hand weighted
> windowing" multiplying a window with the frame of data, without
> implementing an overlap-add function. And secondarily, is right to do a
> "fake overlap-add" simply multiplying sample with a new window function
> that is a sum of a window and it's copy shifted?
>
> Pictorically
>
> MY DATA
> |--------------||--------------||--------------||--------------|
>
> WINDOW (Blackman,triangular, hann...)
> - - - -
> - - - - - - - -
> - - - - - - - -
> - - - - - - - -
>
>
>
Reply by heavyfranz●October 26, 20112011-10-26
Hi, I'm doing a spectrum analyzer. i collect 4096 samples of data from
codec then I stop interrupt and begin fft.
The algoritm that I use ( in the ti's dsplib) does not provide a windowing,
so I don't understand if would be ok to do some "by-hand weighted
windowing" multiplying a window with the frame of data, without
implementing an overlap-add function. And secondarily, is right to do a
"fake overlap-add" simply multiplying sample with a new window function
that is a sum of a window and it's copy shifted?
Pictorically
MY DATA
|--------------||--------------||--------------||--------------|
WINDOW (Blackman,triangular, hann...)
- - - -
- - - - - - - -
- - - - - - - -
- - - - - - - -