Re: Sega sound boards...

Ray Ghanbari wrote:
>
> You wrote:
> > > This is off topic for the vectorlist..so please enlighten me in E-Mail
> >
> > Sure -- leave us all in suspense !

OK, I figured I should have left it alone.. please post it if you ever
decide to type it in Joe. :>

hey, Im learnin' stuff here so this is cool. let me dig a little deeper..
 
> Yeesh! I guess today's schools don't get into Nyquist stuff anymore? ;-)

Not deep enough I guess...

> Practical example:
>
> TV dude has a shirt with horizontal bands. As the camera zooms out, the shirt
> goes nuts and large bands start to appear. In this case, the "signal" is the
> pattern of stripes on the shirt, and the sampling is the vertical pixel spacing
> on the TV. As the spacing between the stripes on the shirt gets to be less
> than the pixel spacing on the TV, aliasing starts. Aliasing folds high
> frequency components into low frequncy components. That's why the "stripes"
> appear to get huge.

But wont aliasing on a TV screen occur before (or in conjunction with)
that period because of the interlaced signal? (sorry....)
 
> Guess what. Square waves sound like a dog shitting in a tin
> can.

man, now I know what that sound is.. :>
 
> How to deal with this easily? (at least with state of the shelf DACs circa
> 1985) Over sampling. In a grossly simplified view, oversampling adds
> additional stair steps to the square signal, making it more "analog"
>like.

so this is part of Quantizing then?

I though oversampling was just for aiding error correction at playback...
in conjunction with that process that scatters the data acoss the disc so
a scratch will not wipe out a good chunk of the data (what was this
process called again?)

Speaking of scratches..that is kinda like how minidisc's compression
works... they added a reeeally well designed error correction circuit and
just didn't record every 5th, 10th, and 15th bit. <hehe>

> Apply a little analog filtering to smooth out the edges, and presumably
>you
> have a nice signal. Apply too much, and things sound like a dog shitting in a
> swimming pool (all muddy).

I thought there was just another low-pass (anti-aliasing) filter after
the D/A convertor.

> Now to sit back and have the real engineers remind me why I'm in
>management now ;-)
and laugh at me and my infinite knowledge. :>

Jeff

-- 
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