From: Bill Stewart <stewarts@ix.netcom.com>
Date: Thu, 24 Aug 95 00:05:28 PDT
To: Andrew.Spring@ping.be (Andrew Spring)
Subject: Re: Random Hiss from Mac mike
Message-ID: <199508240702.AAA24391@ix6.ix.netcom.com>
MIME-Version: 1.0
Content-Type: text/plain


At 07:09 PM 8/23/95 +0100, Andrew Spring wrote:
>In the simplest case, where the microphone is not attached, the signal
>consists of  long runs of '0x80's alternating with '0x7f's.  Now, I have no
>problem transforming this into uniformly distributed RN's : just hash the
>buffer with MD5.

If you know that's what the signal looks like, you can improve it a lot by
run-length encoding before doing the MD5, e.g. crunch the output down to 
a series of count1 value1 count2 value2 count3 value3 (if you stick to runs of
255, you can use 1 byte for each.)   That gives you a much shorter input to
the MD5,
and a more realistic view of how much random data you have.  
(I suppose it may make it harder to do things like Fourier transforms on it...)
#---
#                                Thanks;  Bill
# Bill Stewart, Freelance Information Architect, stewarts@ix.netcom.com
# Phone +1-510-247-0664 Pager/Voicemail 1-408-787-1281
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