[arch-general] OT: [arch-dev-public] polkit package upgrade patch

[Leonid Isaev]

On Sun, 12 Aug 2012 15:01:06 +0000
Fons Adriaensen <fons at linuxaudio.org> wrote:

> On Sun, Aug 12, 2012 at 04:00:47PM +0200, Tom Gundersen wrote:
> 
> > On Sun, Aug 12, 2012 at 3:07 PM, Fons Adriaensen <fons at linuxaudio.org>
> > wrote:
> > > it's just extremely clumsy to use a mixer
> > > that way, you'd need ten hands. For it means that whenever you want
> > > to adjust a single channnel you may have to adjust *all* others and
> > > the master at the same time.
> > 
> > Unlike humans, computers does not have a limited number of hands. This
> > is not a priori a problem.
> 
> It's still like trying to start a 10-ton truck in 5th gear.
> If you do that on your first day on the job you'll be fired,
> not because your boss likes to show his authority but because
> you have shown your incompetence. And if a computerized system
> tries to do that (and maybe it could if it has very fine control
> over the engine and clutch) then there's clearly something wrong
> with it. 
> 
> > > Things will still work well when (A) happens to contribute nothing
> > > (i.e. while it outputs silence). So things will still work well when
> > > (A) isn't there at all. *There is no need to change anything at all*
> > > when (A) goes away, even if all others have their volume set to lower
> > > values.
> > 
> > You have showed that it is unnecessary in one particular (very simple)
> > case. However, you have not showed that it is unnecessary in all
> > cases, so this is not really relevant (had we been talking about a
> > human doing this, you'd have a point of course).
> 
> It is never necessary. It it were that would imply that a sound
> card without any gain controls (equivalent to a fixed 0 dB gain)
> would fail in some cases. It doesn't. In fact many PRO cards are
> just like that.
> 
> If you have apps A, B, C with volumes a, b, c you can always
> set the HW gain to unity gain (0dB), and send 
>   
>   s = a * A + b * B + c * C         (1)

Let me see if I understand. Capital A, B and C are bare intensities (in watts
or logarithmic scale) sent from an app? If those are arbitrarily large, how do
you make sure your speaker is not going to blow up?

> 
> to the soundcard. What would be the advantage of doing what
> PA does, which is
> 
> * m = maximum of a, b, c)
> * Set the master to m,
> * send 
>  
>   s = a/m * A + b/m * B + c/m * C    (2)
>     
> ???
> 
> It can only generate trouble, basically you forfeit any
> headroom the system would have. 

So, the intention is to normalize to the loudest app?

> 
> 
> > > So PA will set the master output to
> > > -20 dB. Now even if all of these apps are limited to contributing
> > > -20 dB (but there is no reason why that should be), the sum of
> > > them can be higher, but your soundcard can't handle that.
> > 
> > That clearly would not work. Surely PA would need to adjust the master
> > output to compensate  for the number of channels? I don't know these
> > implementation details, but I don't see how your arguments shows that
> > this is impossible in general, just that the algorithm you outlined
> > does not work.
> 
> PA could leave some headroom and even adjust that in function
> of the number of sources. But it could also just leave the master 
> gain alone, and compute (1) above instead of (2). Any advantage you
> or any user have from using PA 'things just work' would remain the
> same. But it's a lot simpler and doesn't have the problems (2) has.
> 



-- 
Leonid Isaev
GnuPG key: 0x164B5A6D
Fingerprint: C0DF 20D0 C075 C3F1 E1BE  775A A7AE F6CB 164B 5A6D
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