Good Evening Giuseppe, This gives me weird behavior I can't explain.
Here is my test audio which contains vocals in mono-mid, mono-left, mono-right, mono-half-left, mono-half-right, stereo: https://cloud.4ohm.de/s/y9oZzqFGyrZT5ej And my test code. I only put in the meter instead of three separate outs. import("stdfaust.lib"); //phase(l,r) = (l/r) : aa.arctan; phase(l,r)= (l/r):atan; magnitude(l,r)= (l^2+ r^2)^(1/2); correlate(l,r)= phase(l,r)* magnitude(l,r); correlate_meter(x,y)= x,y<:x,attach(y,(correlate:hbargraph("corr",-1,1))):_,_; process= _,_:correlate_meter; //process = os.osc(10),os.osc(10.1) <: _,_,phase, magnitude, correlate;//, correlate_meter; Another email will follow in response to Dario's solution. Thanks very much! Klaus On 04.08.21 20:47, Giuseppe Silvi wrote: > Hi Klaus, > I suppose the fixed magnitude line is > > magnitude(l,r) = (l^2 + r^2)^(1/2); > > and you can use `atan` in phase(). > > import("stdfaust.lib"); > > //phase(l,r) = (l/r) : aa.arctan; > phase(l,r) = (l/r) : atan; > magnitude(l,r) = (l^2 + r^2)^(1/2); > correlate(l,r) = phase(l,r) * magnitude(l,r); > > correlate_meter(x,y) = x,y <: x , attach(y, (correlate : > hbargraph("corr",-1,1))) : _,_; > > process = os.osc(10),os.osc(10.1) <: _,_,phase, magnitude, correlate;//, > correlate_meter; > >> On 4 Aug 2021, at 16:50, Klaus Scheuermann <kla...@posteo.de> wrote: >> >> Thanks Giuseppe, >> >> I checked it out, but somehow it still does not give me the desired result... >> I did some more research and found this, which indicates that it can be done >> with arctan more easily. >> >>> The way this is done on phase (correlation) meters in audio equipment is >>> rather simple: >>> >>> Phase = arctan(L/R) >>> >>> With phase of 45 or 225 = 1, and phase of 135 and 315 (-45) is -1. >>> >>> Essentially, the Y Axis is the L, and the X axis is the R. The phase is >>> simply the polar angle of the vector between the two. >>> >>> This type of meters will show 1 if the signal is mono, and -1 if the left >>> and right are perfectly phase inverted. >>> >>> Notice however, that phase meters of this type also account for the >>> magnitude in the polar coordinates. So: >>> >>> Magnitude = (L^2 + R^2)^1/2 >>> >>> Thus the actual meter display is a normalised version of: >>> >>> Correlation = Phase * Magnitude >>> >>> I'm not sure that satisfies your requirements, but this answers the >>> question in the subject. >>> >> So I transfered this to faust, but it still behaves weired... >> >> import("stdfaust.lib"); >> >> phase(l,r) = (l/r) : aa.arctan; >> magnitude(l,r) = (l^2 + r^2)^1/2; >> correlate(l,r) = phase(l,r) * magnitude(l,r); >> >> correlate_meter(x,y) = x,y <: x , attach(y, (correlate : >> hbargraph("corr",-1,1))) : _,_; >> >> process = _,_ : correlate_meter: _,_; >> >> Any ideas? >> >> Klaus >> >> On 03.08.21 14:48, Giuseppe Silvi wrote: >>> Hi Klaus, >>> The filters are necessary to obtain a -1 +1 range, I think. >>> >>> import("stdfaust.lib"); >>> >>> correlate(l,r) = l*l ,r*r , l*r : par(i,3, si.smooth(0.9)) : sqrt, sqrt, _ >>> : *,_ : /; >>> correlate_meter(x,y) = x,y <: x , attach(y, (correlate : >>> hbargraph("corr”,-1,1))); >>> >>> process = correlate_meter; >>> >>> Try playing with the si.smooth coefficient. >>> >>> best, >>> giuseppe >>> >>> >>>> On 3 Aug 2021, at 14:09, Klaus Scheuermann <kla...@posteo.de> >>>> wrote: >>>> >>>> Could it be something like this? >>>> >>>> (according to the 'correct' algorithm in >>>> https://www.beis.de/Elektronik/Correlation/CorrelationCorrectAndWrong.html >>>> ) >>>> import("stdfaust.lib"); >>>> >>>> correlate(l,r) = l*l ,r*r , l*r : sqrt, sqrt, _ : *,_ : / :_; >>>> correlate_meter(x,y) = x,y <: x , attach(y, (correlate : >>>> hbargraph("corr",-1,1))) : _,_; >>>> >>>> process = _,_ : correlate_meter: _,_; >>>> >>>> I am not sure about the lowpass filters though. Maybe not needed in the >>>> digital domain? >>>> >>>> Also, my code only returns -1 or 1 while it should be returning a range of >>>> -1 and 1, right? >>>> >>>>> The correlation is either expressed in % from -100% to +100% or as the >>>>> correlation factor, which ranges from -1 to +1. Note that due to the >>>>> correlation algorithm the level of both signals does not matter, i.e., it >>>>> does not influence the measured result. >>>>> >>>>> When a mono source is used for a stereo signal both stereo channels will >>>>> be +100% correlated. When e.g. in a stereo signal both channels contain >>>>> completely different signals, e.g. left (and only left) is the trumpet >>>>> and right (and only right) is the guitar these stereo channels will be 0% >>>>> correlated. With a third instrument appearing in both channels, the >>>>> correlation will be somewhere between 0 and +100%. >>>>> >>>>> >>>> Ideas? >>>> Danke :) >>>> Klaus >>>> >>>> >>>> >>>> >>>> On 03.08.21 12:48, Klaus Scheuermann wrote: >>>> >>>>> Hello List, >>>>> >>>>> I just wondered, if anyone has implemented a stereo audio correlation >>>>> meter/analyser in faust? >>>>> >>>>> If yes - great! >>>>> If no - I have another project :) >>>>> >>>>> Here is what I found about the algorithm(s): >>>>> >>>>> >>>>> https://www.beis.de/Elektronik/Correlation/CorrelationCorrectAndWrong.html >>>>> >>>>> >>>>> >>>>> I never learned analog electronic schematics, but it seems it should not >>>>> be extremely hard to transfer to faust. >>>>> >>>>> Cheers, Klaus >>>>> >>>>> >>>>> >>>>> _______________________________________________ >>>>> Faudiostream-users mailing list >>>>> >>>>> >>>>> Faudiostream-users@lists.sourceforge.net >>>>> https://lists.sourceforge.net/lists/listinfo/faudiostream-users >>>> _______________________________________________ >>>> Faudiostream-users mailing list >>>> >>>> Faudiostream-users@lists.sourceforge.net >>>> https://lists.sourceforge.net/lists/listinfo/faudiostream-users
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