[LAD] update of jkmeter
fons at kokkinizita.net
Tue Oct 7 16:14:01 UTC 2008
On Tue, Oct 07, 2008 at 03:33:34PM +0200, Joern Nettingsmeier wrote:
> what i'm looking for is exactly the behaviour i get from a stereo
> correlation meter (or the W-X one for that matter), where negative means
> out-of-phase, zero means mono and positive means stereo'ish.
That is not what you get from a correlation meter.
+ = in-phase, - = out of phase, 0 = uncorrelated.
If the input is a single frequency, it indicates
the cosine of the relative phase, i.e. zero for
+/- 90 degrees. Mono will indicate +1, as will
any single panned signal, and also a mix of
independent panned signals.
> my intent is to be able to tell at a glance whether a signal has lots of X,
> Y, or Z information. for instance, i would expect the Y and Z meters to
> linger around 0 for an open-air recording of a single musician at the same
> elevation as the microphone. Z would move to 1 when a plane flies overhead
> (or a subway rumbles below), and Y would indicate sounds coming from off
> the median plane.
The problem is that if cx and cy are the outputs of the W/X
and W/Y correlation meters, then atan2(cy, cx) is *not* the
direction of a source. The reason is that they both depend
only on the relative phase of X and Y to W, and not on the
relative amplitudes. Any sound in the left front quadrant
would produce cx = cy = +1.
I am thinking about a graphic display of sound directions
for AMB, but it's a different thing.
Follie! Follie! Delirio vano e' questo!
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