[FFmpeg-devel] [PATCH] swresample/options: change rematrix_maxval default to 1.0

[wm4]

On Sat, 7 Nov 2015 18:33:07 +0100
Michael Niedermayer <michael at niedermayer.cc> wrote:

> On Fri, Nov 06, 2015 at 01:48:59PM +0100, wm4 wrote:
> > On Fri, 6 Nov 2015 12:58:23 +0100
> > Michael Niedermayer <michael at niedermayer.cc> wrote:
> >   
> > > On Fri, Nov 06, 2015 at 11:16:49AM +0100, wm4 wrote:  
> > > > On Fri, 6 Nov 2015 10:54:28 +0100
> > > > Michael Niedermayer <michael at niedermayer.cc> wrote:
> > > >     
> > > > > On Fri, Nov 06, 2015 at 08:52:32AM +0100, Nicolas George wrote:    
> > > > > > Le sextidi 16 brumaire, an CCXXIV, Michael Niedermayer a écrit :      
> > > > > > > iam with whatever default people prefer      
> > > > > > 
> > > > > > IIRC, the current default yields different results when rematrixing from
> > > > > > float to float and then converting from float to int than when doing both in
> > > > > > a single step.      
> > > > > 
> > > > > yes, OTOH float -> float rematrix + "inverse" float->float should be
> > > > > closer to the original than with the changed default
> > > > > The difference between the defaults is in volume of the output
> > > > > 
> > > > >     
> > > > > > I beliee this is not good.      
> > > > > 
> > > > > no its not good, though the alternative isnt really good either.
> > > > > All choices have some kind of disadvantage. There also would be the
> > > > > possibility of implementing 2 pass mode to maintain the volume as much
> > > > > as possible without cliping (but that could not easily be default)
> > > > > For the default, the question is what people prefer ...    
> > > > 
> > > > Do you mean some kind of DRC?    
> > > 
> > > no but that would be another possibility as well  
> > 
> > Then I don't know what you meant by this 2 pass mode. Can you explain?
> > I'm interested in obtaining better downmix.  
> 
> i just meant a 2pass mode that would linearly scale the output so
> volume is maintained between input and output as good as possible
> without cliping (that is apply the same scaling factor to all channels
> and all points in time)

I still don't understand. Isn't this done already?