Path: utzoo!mnetor!uunet!husc6!mit-eddie!ll-xn!ames!pasteur!agate!saturn!ucscb.UCSC.EDU!alibaba
From: alibaba@ucscb.UCSC.EDU (Alexander M. Rosenberg)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Sound Techniques
Message-ID: <2303@saturn.ucsc.edu>
Date: 10 Mar 88 09:18:44 GMT
References: <2263@saturn.ucsc.edu> <24846@yale-celray.yale.UUCP>
Sender: usenet@saturn.ucsc.edu
Reply-To: alibaba@ucscb.UCSC.EDU (Alexander M. Rosenberg)
Organization: University of California, Santa Cruz; CATS
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I thought I'd try and follow up here. What I've deterined is
that all the BDC sounds are at 5.5kHz, and the so-called "compression"
is really a method similar to the way that fat-bits are made (this
may be an old fat bits technique, it came from the Byte SmallTalk issue)

Each bit it plotted every 9 pixels. it is then replotted one to the
right 8 times. (This produces horizonal lines.) then the lines are
duplicated vertically eight times. This produces fat bits. I think
something similar is occuring with BDC sound technique. The sounds
are only every x samples, then "streched" to produce what sounds like
a better sampling rate, and a fuller sound. It also explains the
tinny echo effect that the sounds sound like when not "uncompressed."

Anybody know anything about doing this sort of thing? BDC has good
sounding sounds, and it only stores little bits of them.\

BTW, this fat bits technique also explains how sounds can be overlaid.
Instead of screching the sound, inserting another one interwoven, will
produce the effect of overlapping sounds. I ay have to experiment with
this as it seems a good way of storing sound for low-quality playback
and overlay. If Apple would ever docuemnt 'snth' resources properly,
I would even consider writing a 'snth' to do this, as well as a sound
filter to shrink sounds down.

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