Re: Windowed-sinc function


BobM wrote:
> Michel Rouzic wrote:
> > I tried changing my code by what you gave :
> >
> > for (i=0; i<*M/2; i++)
> > {
> > h[i]=sin(2*pi*fc*(i-*M/2))/(pi*(i-*M/2));
> > h[*M-i-1]=h[i];
> > }
> > h[*M/2]=2*fc;
> >
> > an apparently, it doesn't change alot. the highest sample besides the
> > central one is still only 1.8506121e-008
>
> That factor alone might be meaningless. What is it doing in the
> frequency domain?

as one could expect, not alot, it acts alot like a shifted delta
function

> > I also looked at your code http://www.musicdsp.org/files/wsfir.h and,
> > correct me if i'm wrong, but doesn't your blackman window end and start
> > with 0 values?
>
> Yes...
>
> I double-checked a couple of books (Oppenheim & Schafer and Rick
> Lyons's latest) and both show the Blackman window starting and ending
> with 0. Off the top of my head, the one common window notable for _not_
> starting/ending with 0 is the Hamming window.

oh, I thought zeros were useless for a blackman window. guess i'll have
to correct my code

> > anyways, i dont understand why it worked for you and not me if we're
> > using the same formulas...
>
> Not sure. Good luck!
>
> Michel, if you haven't done so already I highly recommend getting a
> hold of a couple of good DSP text books. I recommend Understanding DSP
> by Richard Lyons for starters. Your questions have served as good
> discussion topics, although I think most of your code issues could have
> been solved with a quick reference to a DSP book to brush up on the
> concepts.

yeah i'm getting kind of tired of always having to ask for help on
usenet. From what I see on amazon, it sounds like a very good book.
i'll buy it as soon as i can (whenever i get a job). btw, is the second
edition really worth the price difference?

.

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