Re: [stella] interesting supercharger/mp3 challenge

Subject: Re: [stella] interesting supercharger/mp3 challenge
From: "Eric Ball" <ericball@xxxxxxxxxxxx>
Date: Wed, 3 Mar 2004 20:01:39 -0500
> 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.

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.

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