[linux-audio-dev] Final Scratch, custom kernel?

[Paul Winkler]

On Mon, Oct 07, 2002 at 09:18:38PM +0200, CK wrote:
> > you could just count the zero crossings per second and take the ratio
> > compared to the expected 440 Hz.

But DJ techniques include manipulating the speed of the record -
faster or slower.  So if all you do is measure frequency, you won't 
know whether you've increased the position or the speed.

So I think something like the suggestion of stereo-encoding two
signals is necessary. That way the speed and direction can always
be determinied by looking at the sawtooth wave, e.g. on the left channel,
as suggested previously;
and the *position* can be determined by comparing the  ratio of 
the sawtooth wave to a time-varying signal on the right channel.

Encoding stereo to an LP is no problem - the needle vibrates along
two axes.  There's a limit to how much stereo separation you can
get (I forget, it might be like 40-45 dB) but that shouldn't be
too hard to account for.

--PW

--

Paul Winkler
"Welcome to Muppet Labs, where the future is made - today!"