comp.dsp conference: Still need presenters? How about ...

TITLE:"Fast Convolution (FFT) Filtering: From Basics to Filter Banks".

DESCRIPTION: Fast Convolution filtering is a powerful technique with 
which every DSP engineer should be familiar.  All but the shortest FIR 
filters are more efficiently implemented with FFTs rather than direct 
forms.  The longer the filter; the greater the advantage.  This 
presentation begins with the primary forms of fast convolution: 
overlap-add and overlap-save.  These concepts lay the foundation for 
building parallel filters that perform mixing, filtering, and 
downsampling in the frequency domain.



I was thinking that demonstrating the concepts via matlab/octave scripts 
on an LCD projector would be a good format.

There will be approximately 6-10 iterations of the script, each one 
building on the previous concepts.

I'll start by demonstrating circular convolution of two sequences using 
an FFT.
Then add the overlapping transients of successive buffers.
Then explain the computational benefit of overlap-save.
...etc
In the end, the script will model a system that:
    performs an fft on each overlapping input block,
then for each output filter/tuner:
    mixes via bin-shifting,
    multiplies by an anti-alias filter's frequency response,
    wraps/aliases the residual high frequency energy to the lower bins
    reverse ffts with a smaller transform size than the forward fft to 
decimate
    discards the wrap-around transients.


I think it will fit into an hour with sufficient links for further study.
It could also be easily split into two sessions.

-- Mark Borgerding

Mark Borgerding <mark@borgerding.net> wrote in news:409C4C21.9010408
@borgerding.net:

> TITLE:"Fast Convolution (FFT) Filtering: From Basics to Filter Banks".
> 
> DESCRIPTION: Fast Convolution filtering is a powerful technique with 
> which every DSP engineer should be familiar.  All but the shortest FIR 
> filters are more efficiently implemented with FFTs rather than direct 
> forms.  The longer the filter; the greater the advantage.  This 
> presentation begins with the primary forms of fast convolution: 
> overlap-add and overlap-save.  These concepts lay the foundation for 
> building parallel filters that perform mixing, filtering, and 
> downsampling in the frequency domain.
> 
> 
> 
> I was thinking that demonstrating the concepts via matlab/octave 
scripts 
> on an LCD projector would be a good format.
> 
> There will be approximately 6-10 iterations of the script, each one 
> building on the previous concepts.
> 
> I'll start by demonstrating circular convolution of two sequences using 
> an FFT.
> Then add the overlapping transients of successive buffers.
> Then explain the computational benefit of overlap-save.
> ...etc
> In the end, the script will model a system that:
>     performs an fft on each overlapping input block,
> then for each output filter/tuner:
>     mixes via bin-shifting,
>     multiplies by an anti-alias filter's frequency response,
>     wraps/aliases the residual high frequency energy to the lower bins
>     reverse ffts with a smaller transform size than the forward fft to 
> decimate
>     discards the wrap-around transients.
> 
> 
> I think it will fit into an hour with sufficient links for further 
study.
> It could also be easily split into two sessions.
> 
> -- Mark Borgerding
> 

Wonderful!

Lori Ann or Rick will get you on the schedule.

-- 
Al Clark
Danville Signal Processing, Inc.
--------------------------------------------------------------------
comp.dsp conference July 28 - Aug 1, 2004

details at http://www.danvillesignal.com/index.php?id=compdsp
email: compdsp@danvillesignal.com

Who says you can't teach an old dog a new DSP trick?