ODP: AW: Harmonix content formula

[Martin Czech]

> I stayed quiet on this subject, cuz I've seen many posts describing it
> in detail. But when you say FFT is a headache I have to dissagree.
> I'd say it is fun (see how dorky I am). You could probably find many
> examples
> of software (I mean source code) calculating FFT, or even write your own
> when you learn the FFT itself. It is rather simple and logical IMHO.
> And FFT examples for DSPs are just laying around everywhere.
> If anyone is interested in C code for it, I'd be pleased to share with you.
> Not too efficient code, but works (for Windoze).
> BTW, I've heard of strange ppl doing FFT in hardware (8-O
> using FPGA chips. It was also one of the project in my University,
> but I don't know if they succeded.

Not strange. If you want to do fast convolution in real time for video,
you'll need some fast hardware, it is 2D, so even more power is needed.

> 
> Now I have dangerously silly idea - DCT in analog hardware:
> (Discrete Cosine Transform - simplifed version of Discrete Fourier
> Transform)
> say, 32 sine oscilators of harmonic frequencies (or not harmonic - why stick
> to the original?), 32 multipliers (ringmods) multiplying input signal with
> each of
> 32 sine oscs (or one muxed), 32 envelope followers and we have harmonic
> content output.
> 
???

sorry

My understanding is that FT looks like convolution with sine waves,
not multiplying. That would be too easy.

If you see it this way, FT is like filtering and the filter impulse
response is a sin/cos wave.

m.c.