Xref: utzoo rec.audio:21781 sci.electronics:12269
Path: utzoo!utgpu!watserv1!watmath!att!dptg!ulysses!andante!alice!jj
From: jj@alice.UUCP (jj, like it or not)
Newsgroups: rec.audio,sci.electronics
Subject: Re: My CD player is running slow! (!)
Message-ID: <10903@alice.UUCP>
Date: 5 Jun 90 02:18:26 GMT
References: <1990Jun2.182334.21396@athena.mit.edu> <6378.26693284@umiami.miami.edu> <55024@microsoft.UUCP>
Reply-To: jj@alice.UUCP (jj, like it or not)
Organization: NJ State Home for Bewildered Terminals
Lines: 41

In article <55024@microsoft.UUCP> gordonl@microsoft.UUCP (Gordon LETWIN) writes:
>In article <6378.26693284@umiami.miami.edu>, chuck@umiami.miami.edu writes:
>> 
>> There is no way in the world that the CD player would play "slow" or "flat"
>> because of the nature of the beast.  ...
>> ...Pitch-shifting in the 
>> digital domain is a fairly ugly computational process, usually handled by
>> high-speed DSP chips.  
>
>This is wrong.  Pitch shifting is easy.  My first CD player was an
>inexpensive one and it had a pitch adjustment control on it.  It's my
>guess that you can pitch shift just by changing the rate at which you
>feed samples to the DtoA convertor.  CD players already have circuitry
>to adjust the rotation rate to keep the convertor FIFO happy, so I expect
>that if you just change your sample clocking rate the slight change of
>the disc rotation rate would occur automatically.

Whoa.  This is confusing two things:
	1) Slow playback
	2) Pitch shifting.

They are different.  1) involves slowing down the whole system,
and will slow down both the cadence and pitch of the signal.

2) involves doing information lossy signal processing of entirely
non-trivial nature.

It's very easy to imagine that the CD player has a bad crystal
(doesn't matter why) that is 1% slow.  1% is easily heard as a pitch
uncertainty.

Of course, when tape machines are involved, one wonders if the
mechanics of the tape machine aren't involved in the process,
perhaps through drag problems, or machine to machine variations.

Neither need involve the CD player.
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