7 Oct
2002
7 Oct
'02
7:36 p.m.
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!"