Subject: Re: [linux-audio-dev] learning DSP?
From: andrew_AT_acooke.org
Date: Fri Dec 21 2001 - 12:03:39 EET
This is from ancient memory (I'm reading this list out of curiousity
and haven't done any DSP for years). IIRC, you want to search for
info on Z transforms, which are the discrete equivalent of S
transforms which are just Laplace transforms by a different name. I
come from a physics/maths background (rather than an engineering one)
and remember being rather frustrated with the way engineering
textbooks don't explain the fundamental maths in the style I was used
to (and make up names for everything! ;-) - if you're from a similar
background, you may find any popular book with "engineer" in the title
a bit frustrating. Apologies to engineers - this is just a different
emphasis in approach, not a better/worse thing.
Googling for laplace and z transforms I came across
http://lorien.ncl.ac.uk/ming/digicont/digimath/sampled3.htm which
looks like a good brief summary of the basics.
Andrew
On Fri, Dec 21, 2001 at 03:54:09PM +1100, Stuart Allie wrote:
> Okay, Paul's initial explanation and Lamar's comments make it (eq via delay
> lines) fairly obvious in hindsight, thanks guys.
>
> To switch topic a bit, I just came across "The Scientist and Engineer's
> Guide to Digital Signal Processing" on the web - does anybody have any
> comments about the quality of this as an intro to DSP? Any recommendations
> for other DSP sources?
>
> TIA
> Stuart
>
>
> > On Wednesday 19 December 2001 08:39 pm, Paul Davis wrote:
> > > >Just curious, but could somebody explain *how* delay lines
> > can be used
> > > >implement EQ? I have a strong maths background, but no DSP
> > experience if
> > > >that helps.
> >
> > > i'm not a dsp programmer, but its really quite simple. if you
> > > feedback with a delay of just 1 sample, and attenutate both the
> > > current and previous sample by 0.5:
> >
> > > the actual details are extremely hairy though - there is a lot of
> > > sophisticated math that goes into really good filter design, plus a
> > > lot of subjective, non-double blind tested "opinion" :)
> >
> > In short: Z transforms are your friend. Once I grasped what
> > the Z transform
> > did for you in control systems theory, I immediately realized
> > that filtering
> > is a natural for Z transform math.
> >
> > But, in a nutshell:
> >
> > Delaying a set time and adding back to the original produces
> > a 'comb' filter.
> > The amount of the delay and the depth of the readdition
> > together produce
> > various degrees of filtering. Notch filters are easiest with
> > delays -- delay
> > one half cycle at the notch and add back one hundred percent.
> > You get a
> > rather tight notch. Along with other neat effects. :-) Like
> > the peak at
> > twice the notch frequency.... :-) And the secondary notch at
> > thrice the
> > notch frequency. Even multiples peak, odd multiples notch --
> > thus a comb
> > filter.
> >
> > Comb filters are used rather nicely in chroma/luma separation
> > in Never The
> > Same Color video.
> > --
> > Lamar Owen
> > WGCR Internet Radio
> > 1 Peter 4:11
> >
>
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