scaling in a fixed point FFT

Hi.

I'm writting a code to do a FFT using fixed point(16 bits). Well this
is the question What is the better, make the sacaling after or before
start a pass. I think that is better before start a pass. This is
correct?


Diego

DX wrote:
> Hi.
> 
> I'm writting a code to do a FFT using fixed point(16 bits). Well this
> is the question What is the better, make the sacaling after or before
> start a pass. I think that is better before start a pass. This is
> correct?

Processor?
-- 
Engineering is the art of making what you want from things you can get.
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| I'm writting a code to do a FFT using fixed point(16 bits). Well 
this
| is the question What is the better, make the sacaling after or 
before
| start a pass. I think that is better before start a pass. This is
| correct?
|

If results are divided by two to avoid overflow at each stage (like 
the code I use)
You better scale your input buffer before processing the FFT.

Of course it depends of the precision you need !

Yes, it depends about the presicion, but it depends about the dsp's
features to.
The problem is that I have to use fixed point and the registers has 16
bits to represent a fixed point, and if I don't scale the data they
overflow the registers.

Thank you.

Diego

Hi,

It's better to do the scaling inside the FFT when the intermediate
results have grown. Or even better do a data dependent scaling inside
the FFT when needed.

Best regards,
Jens J. Nielsen
http:/home.get2net.dk/jjn

On 25 Jul 2005 13:48:53 -0700, "DX" <diux007@gmail.com> wrote:

>Yes, it depends about the presicion, but it depends about the dsp's
>features to.
>The problem is that I have to use fixed point and the registers has 16
>bits to represent a fixed point, and if I don't scale the data they
>overflow the registers.
>
>Thank you.
>
>Diego