[LAD] update of jkmeter

[Fons Adriaensen]

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.

Ciao,

-- 
FA

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