Re: [stella] interesting supercharger/mp3 challenge

Subject: Re: [stella] interesting supercharger/mp3 challenge
From: KirkIsrael@xxxxxxxxxxxxx
Date: 4 Mar 2004 01:24:56 -0000
> > I had this idea for using my friends "ancient" mp3
> > player (a Diamond Rio, a 'paltry' 32 megs) as a way of carrying
> > around an mp3 version of the JoustPong "makewav" output.
> >
> > At first it was hit or miss whether it worked, but now I
> > figured out how to crank up the bitrate (so the mp3 is nearly
> > as big as the Wav ~250k) and it seems to be pretty reliable.
> Many (most?) MP3 players grok WAV files too.  Just toss an 8KHz mono WAV
> file from MakeWAV onto it and see if it will play it back.

Well, I've only found one program that lets me deal w/ the Rio
that runs under XP (its kind of klunky, with a printer port 
passthrough adapater (!)) and it only accepts mp3 files.  

> MP3 uses a DCT to transform the PCM input to a pseudo-frequency space.  The
> problem is each DCT term represents a cosine wave at a single frequency &
> defined phase shift.  So even if the frequency is matched, only the in phase
> portion is preserved, the rest gets smeared across the entire DCT spectrum.
> In between frequencies get treated even worse.  And that's before the
> quantization algorithm decides to reduce the resolution or chop out chunks
> of the spectrum.  MP3 is fine for music & speech, but horrid to anything
> which requires very accurate reproduction.

You know, that's EXACTLY what I was thinking before my friend 
convinced me to try it...well, except for the bit about the cosine 
wave. And the phase shift.  And the DCT spectrum.  And the quantization.
But I DID think MP3 might be removing the bits that aren't important
to our ears, like JPEG does for images, and that those bits might be 
important to the supercharger.  So I was surprised that it work. Well, 
I figured it had to be a little robust, since old tape players were
rather lofi but it had to work despit that.  

At the higher bit rate, it seems pretty reliable, but I'll 
burn a CD and bring a discman as back up :-) Just wont look 
as cool...the supercharger/mp3 combo looks pretty slick, actually.

"If I can't be free, at least I'll be cheap"--some guy on the net

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