Date   : Mon, 12 Feb 1996 17:25:49 +0100
From   : Robert Schmidt <robert@...>
Subject: Re: Decoding BBC tapes...

At 15:47 12.02.96 +0100, you wrote:
>Maby it is possible to take smaller sound-samples, maby 2400 times pr. sec.
Every
>sound-sample should be long enough to enclose two successive zero
crossings. You
>only have to measure the time between the two crossings. Of course this
method
>would be more sensitive to noise, but then you could try to take more
sound-samples
>pr. sec. (make it a variable). I would love to program this, but i am
long away
>from home and my BBC :-(

I didn't get this.  If you sample at 2400 Hz, you should be lucky to detect
anything at all.  The "0" frequency is exactly 2400 Hz, so your sample can
(in theory) be all zeroes.  If you're lucky, "0" will show as "++" (or
"--"), while "1" will show as either "+-" or "-+".

But actually it's not too bad an idea, but I would rather sample at a
greater multiple of 2400 Hz, maybe 4800 will do, though 9600 sounds quite
safe.  This would reduce the amount of data to process substantially - I
guess 44100 is not really neccessary.  I wish I knew more of the theory
behind all this.

robert

--
Robert Schmidt - robert@...         - http://www.idt.unit.no/~robert
	
	Maintainer of "The BBC lives!" page:  
	http://www.idt.unit.no/~robert/bbc/bbc.html