[LAU] Filtering out everything but the centre position in stereo

James Harkins jamshark70 at zoho.com
Fri Aug 23 13:50:48 CEST 2019

On Aug 22 2019, Ralf Mardorf has written:
> ...
>> On the quick my guess is
>> Original left  channel + inverted right channel = plain_left
>> Original right channel + inverted left  channel = plain_right
>> Original left  channel + inverted plain_left    = middle only
>> Original right channel + inverted plain_right   = middle only
> ...
> That sounds good. Unforunately it didn't work.

I went down that road once before.

"Plain" channels:

a = l - r ("side" in mid/side)
b = r - l

Then l - a = l - (l - r) = r and r - b = r - (r - l) = l, neither of which 
isolates the center.

The idea of the karaoke effect is to cut in-phase material that is in 
common between the channels (e.g. often lead vocals). You'd think you can 
do the karaoke effect and then some subtraction would leave you with 
"whatever is not the karaoke effect," but in fact, variables cancel out in 
a way that you don't get anything useful. This might be the reason why you 
don't find a lot of plugins for this.


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