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Author Topic:   Phase Meter
SSC
Administrator 		posted 03 July 2002 14:27         Edit/Delete Message   Reply w/Quote

phasemeter.kym
 
Mathis inspired us to implement a phase meter. This allows you to measure the average phase difference between the right and left channels of a stereo input. In some sense, it gives a measure of the "stereo separation" of your signal. It can also warn you if your stereo signal will cancel itself out in a mono mix (e.g. for TV or radio).

In each of these Sounds, you will find the input to the phase meter to be the replaceable input Sound, called "source".

In addition to monitoring the stereo source, the output of the Sound is a meter/fader (controlled by a SoundToGlobalController) called "Phase". When Phase is at the top, the left and right channels of the input Sound are perfectly in phase; the middle of the fader indicates a 90 degree phase difference between the left and right channels; and the bottom indicates a 180 degree phase difference.

This meter works by measuring the instantaneous phase difference between the left and right channels (using the ArcTangent Sound). It maps the phase difference to a -1 to +1 range (using the InputOutputCharacteristic Sound), where -1 indicates 180 degrees and +1 indicates zero degrees. Then it smooths the (-1, 1) output using a 10 hz cutoff AveragingLowPassFilter, and, finally, it translates the measurement to an Event (using the SoundToGlobalController Sound) that is displayed on the VCS .

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mathis
Member 		posted 03 July 2002 15:38         Edit/Delete Message   Reply w/Quote
congratulations!! iīm completely enthusiastic!!
thatīs exactly what i whished!!!
thank you very very much!

itīs very accurate and expressive. for me itīs not only the possible loss of sound when playing it back mono for which i have to care for, also the opposite: when a sound is too much out of phase it moves too much in the surround speakers when played back thru a dolby stereo decoder (analog matrix).


(the only thing i changed for me: iīm used to see the correlation meter in horizontal position.)

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mathis
Member 		posted 04 July 2002 15:33         Edit/Delete Message   Reply w/Quote

phasemeter_v2.kym
 
Kurt helped me with enourmous perseverance during a long long phone call bringing the phase meter to my taste. thank you very much, kurt.

1) after comparing it to known correlation meters i found out that they have a different ballistic to show more detail in the 90° area (in the middle). (like in level meters, where the area around 0dB has higher resolution). its new ballistic is now nearly the same as that of the "professional" correlation meters.
this helps also for not being too cautious with phasey material. now it looks more safe. which is right.
2) changed smoothing/time resolution to 1 hz.
3) changed vertical to horizontal fader.

[This message has been edited by mathis (edited 04 July 2002).]

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