[Flac] understanding decorrelation

[Josh Coalson]

--- Ulrik Nissen <obbarius at rediffmail.com> wrote:
>   
> Hi FLACers
> 
> I'm studying music production and am currently doing an analysis of
> the FLAC format. If anyone has the knowledge and a minute to explain
> i would greatly appreciate any help. One thing that i cannot make
> sense from in the FLAC documentation (a thing that is hard to find
> info on in general) is how the decorrelation fase works exactly. I
> understand that the two channels in a stereo file can have
> similarities that can be exploitet when compressing, but why is this
> transformation used: mid = (left + right) / 2, side = left - right?
> Is it simply to straighten out the signals and thereby having less
> information to compress? 

it's a simple way to try and move information that is in both
channels into one so it only has to be represented once.

calculate by hand the transformation on a stereo file with 2
identical channels and see what you get.  this is the optimal case.

Josh


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