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From: simard@loral.UUCP (Ray Simard)
Newsgroups: net.audio
Subject: Re: speeding up sound
Message-ID: <288@loral.UUCP>
Date: Fri, 27-Jul-84 02:21:54 EDT
Article-I.D.: loral.288
Posted: Fri Jul 27 02:21:54 1984
Date-Received: Sun, 22-Jul-84 05:47:50 EDT
Organization: Loral Instrumentation, San Diego, CA
Lines: 34



Digital "harmonizers" work basically by sampling the input signal, storing the
signal in a memory buffer, while simultaneously outputing the signal at a 
different rate.  Some smarts are usually included so that when the output
pointer is at a zero crossing and about to overtake the input pointer, the 
output pointer is reset to a previous zero crossing, thus eliminating the
glitch that occurs when the output pointer overtakes the input pointer.  The 
effect can be observed even without this zero-crossing matching however, as
I have used an 8080 and 8 bit a/d d/a converters to do some experimenting
with this technique.  The buffer size I use is relatively small in this case,
512 to 1024 bytes.

This has the effect of 're-playing' the most recent completed wave in
order to make up for the fact that the playback is occuring faster than
the record.


I would have posted this message to the net, however we seem to be having
a problem with our mail system at this time and can only mail to specific
destinations.  If you feel it might be useful, please post from your end.

Keith Doyle
{ucbvax,decvax}!trwrb!cadovax!keithd

>Per Keith's request, I have posted this to net.audio.



-- 
Ray Simard
Loral Instrumentation, San Diego
{ucbvax, ittvax!dcdwest}!sdcsvax!sdccsu3!loral!simard