[MPlayer-dev-eng] [PATCH] Automatic downmix

[Clément Bœsch]

On Mon, Sep 20, 2010 at 06:25:09PM +0200, Tobias Diedrich wrote:
> A bit late into the discussion, but...
> 
> Clément Bœsch wrote:
> >  /*                FL       FR       RL       RR          FC          LF         AL      AR */
> >  [3] = "pan=2:" "0.6:0:" "0:0.6:"                     "0.4:0.4",
> >  [4] = "pan=2:" "0.6:0:" "0:0.6:" "0.4:0:"  "0:0.4",
> >  [5] = "pan=2:" "0.5:0:" "0:0.5:" "0.2:0:"  "0:0.2:"  "0.3:0.3",
> >  [6] = "pan=2:" "0.4:0:" "0:0.4:" "0.2:0:"  "0:0.2:"  "0.3:0.3:"   "0.1:0.1",
> >  [7] = "pan=2:" "0.4:0:" "0:0.4:" "0.2:0:"  "0:0.2:"  "0.3:0.3:"              "0.1:0:" "0:0.1",
> >  [8] = "pan=2:" "0.4:0:" "0:0.4:" "0.15:0:" "0:0.15:" "0.25:0.25:" "0.1:0.1:" "0.1:0:" "0:0.1",
> 
> I was wondering how you decided on the coefficents?
> Apart from 'Everthing should add up to 1', some look rather
> arbitrary.

Yes they are… I asked at the beginning of the thread if anyone has better
values to propose.

> For example I'd expect center and low frequency effects to have the
> same coefficients.
> It's also inconsistent, because for 6&7 FC/LF is 3, while for 8
> channels FC/LF is 2.5...
> 

Yes, it was to follow the "Everything should add up to 1" you mentionned"

> Googling a bit turns up
> http://forum.doom9.org/archive/index.php/t-57170.html
> and
> http://forum.doom9.org/showthread.php?s=&threadid=27936
> and
> http://www.atsc.org/cms/standards/a_52b.pdf
> 
> I think optionally using a Pro Logic matrix would make some sense
> because some people may have a pro logic surround amplifier
> connected to the stereo output.
> 
> For example:
> 
> Lt = 1.0*L + 0.707*C + 0.707*LFE - 0.8165*Ls - 0.5774*Rs
> Rt = 1.0*R + 0.707*C + 0.707*LFE + 0.5774*Ls + 0.8165*Rs
> 

That sure could be used for one case. I'm going to test those values, and
see if I can adapt them to all the other input channels case.

> And with downscaling:
> 
> Lt = .2626*L + .1856*C + .1856*LFE - .2144*Ls - .1516*Rs
> Rt = .2626*R + .1856*C + .1856*LFE + .1516*Ls + .2144*Ls
> 
> -- 
> Tobias						PGP: http://8ef7ddba.uguu.de

Thanks,

-- 
Clément B.