[LAD] Mixing audio: Implementing pan and balance

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To: <linux-audio-dev@...>
Date: Tuesday, March 12, 2013 - 5:23 am

Hi, I need some advice, clear up some confusion:

I noticed our app uses this pan formula:

vol_L = volume * (1.0 - pan);
vol_R = volume * (1.0 + pan);

where volume is the fader value, pan is the pan knob value
which ranges between -1.0 and 1.0, and vol_L and vol_R are the
factors to be applied to the data when sending a mono signal
to a stereo bus.

When pan is center, 100% of the signal is sent to L and R.
At pan extremities, the signal is boosted by 3dB.

But according to [1], we should be using a Pan Law [2],
where pan center is around 3dB to 6dB down and pan
extremities is full signal.

So I want to change how we mix mono -> stereo and use
true Pan Law. I could add a Pan Law selector, seems like it
might be useful for various studio acoustics.

Then I noticed we use the same formula above to apply 'balance'
(using the same pan knob) when sending a stereo signal to
a stereo bus.

But according to [3] we should be using a true balance control, not those
same pan factors above. And according to [1]:
"Note that mixers which have stereo input channels controlled by a single
pan pot are in fact using the balance control architecture in those channels,
not pan control."

So I want to change how we mix stereo -> stereo and use true balance.

But then I checked some other apps to see what they do.
In an unofficial test I noticed that QTractor seems to do the same thing,
that is, when pan is adjusted on a stereo track, one meter goes up while
the other goes down. RG seems not to have stereo meters and Ardour
I couldn't seem to make pan affect the meters, I will try some more.

My questions:

Is the pan formula above popular?

What is the consensus on stereo balance - use a Pan Law, being the
formula above or otherwise, or use a true balance?

What should I do in the remaining case sending a stereo signal to a mono bus?
If I am using a Pan Law as balance, the two signals will have already been
attenuated at pan center so I could simply sum the two channels together.
But if instead I use true balance, at center the two signals are 100%.
So should I attenuate the signals before summing them to a mono bus?
Currently as our pan formula above shows, there would be no attenuation.

Thanks.
Tim.

[1]
http://en.wikipedia.org/wiki/Panning_%28audio%29
[2]
http://en.wikipedia.org/wiki/Pan_law
[3]
http://www.rane.com/par-b.html#balance

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Messages in current thread:
[LAD] Mixing audio: Implementing pan and balance, Tim E. Real, (Tue Mar 12, 5:23 am)
Re: [LAD] Mixing audio: Implementing pan and balance, Fons Adriaensen, (Tue Mar 12, 9:56 am)
Re: [LAD] Mixing audio: Implementing pan and balance, Tim E. Real, (Tue Mar 12, 8:25 pm)
Re: [LAD] Mixing audio: Implementing pan and balance, Fons Adriaensen, (Tue Mar 12, 9:22 pm)
Re: [LAD] Mixing audio: Implementing pan and balance, Tim E. Real, (Wed Mar 13, 8:16 am)
Re: [LAD] Mixing audio: Implementing pan and balance, Paul Davis, (Wed Mar 13, 11:34 am)
Re: [LAD] Mixing audio: Implementing pan and balance, Paul Davis, (Tue Mar 12, 8:28 pm)
Re: [LAD] Mixing audio: Implementing pan and balance, Tim E. Real, (Tue Mar 12, 9:15 pm)
Re: [LAD] Mixing audio: Implementing pan and balance, Geoff Beasley, (Tue Mar 12, 9:41 am)
Re: [LAD] Mixing audio: Implementing pan and balance, Tim E. Real, (Tue Mar 12, 7:08 pm)
Re: [LAD] Mixing audio: Implementing pan and balance, Jörn Nettingsmeier, (Thu Mar 14, 10:42 am)
Re: [LAD] Mixing audio: Implementing pan and balance, Tim E. Real, (Fri Mar 15, 11:57 pm)
Re: [LAD] Mixing audio: Implementing pan and balance, Paul Davis, (Thu Mar 14, 11:37 am)
Re: [LAD] Mixing audio: Implementing pan and balance, Jörn Nettingsmeier, (Thu Mar 14, 6:50 pm)
Re: [LAD] Mixing audio: Implementing pan and balance, Ralf Mardorf, (Sat Mar 16, 10:17 am)
Re: [LAD] Mixing audio: Implementing pan and balance, Fred Gleason, (Sat Mar 16, 11:51 pm)
Re: [LAD] Mixing audio: Implementing pan and balance, Ricardus Vincente, (Sat Mar 16, 7:47 pm)
Re: [LAD] Mixing audio: Implementing pan and balance, Paul Davis, (Sun Mar 17, 10:54 am)
[LAD] OT: Mixing audio: Implementing pan and balance, Ralf Mardorf, (Sat Mar 16, 2:20 pm)
Re: [LAD] Mixing audio: Implementing pan and balance, Paul Davis, (Sat Mar 16, 1:25 pm)
Re: [LAD] Mixing audio: Implementing pan and balance, Fons Adriaensen, (Sat Mar 16, 6:23 pm)
Re: [LAD] Mixing audio: Implementing pan and balance, Raphaël BOLLEN, (Sat Mar 23, 5:05 pm)
Re: [LAD] Mixing audio: Implementing pan and balance, Raphaël BOLLEN, (Sun Mar 24, 8:07 am)
Re: [LAD] Mixing audio: Implementing pan and balance, Raphaël BOLLEN, (Sun Mar 24, 8:46 am)
Re: [LAD] Mixing audio: Implementing pan and balance, hermann meyer, (Sun Mar 24, 9:50 am)
Re: [LAD] Mixing audio: Implementing pan and balance, Raphaël BOLLEN, (Sun Mar 24, 10:10 am)
Re: [LAD] Mixing audio: Implementing pan and balance, Jörn Nettingsmeier, (Sun Mar 24, 12:57 am)
Re: [LAD] Mixing audio: Implementing pan and balance, Fons Adriaensen, (Sun Mar 24, 11:57 am)
Re: [LAD] Mixing audio: Implementing pan and balance, Raphaël BOLLEN, (Sun Mar 24, 1:01 pm)
Re: [LAD] Mixing audio: Implementing pan and balance, Fons Adriaensen, (Sun Mar 24, 3:11 pm)
Re: [LAD] Mixing audio: Implementing pan and balance, Raphaël BOLLEN, (Sun Mar 24, 4:18 pm)
[LAD] zita-mu1 denormals, Fons Adriaensen, (Wed Mar 27, 11:48 am)
Re: [LAD] zita-mu1 denormals, Raphaël BOLLEN, (Wed Mar 27, 2:21 pm)
Re: [LAD] Mixing audio: Implementing pan and balance, Ralf Mardorf, (Sat Mar 16, 8:28 pm)
Re: [LAD] Mixing audio: Implementing pan and balance, Ralf Mardorf, (Sat Mar 16, 10:21 am)
Re: [LAD] Mixing audio: Implementing pan and balance, Paul Davis, (Thu Mar 14, 7:01 pm)
Re: [LAD] Mixing audio: Implementing pan and balance, Tim E. Real, (Tue Mar 12, 7:21 pm)
Re: [LAD] Mixing audio: Implementing pan and balance, Paul Davis, (Tue Mar 12, 7:13 pm)
Re: [LAD] Mixing audio: Implementing pan and balance, Tim E. Real, (Tue Mar 12, 7:44 pm)