[FFmpeg-devel] [PATCH] pngdec: set correct range

Carl Eugen Hoyos cehoyos at ag.or.at
Fri May 8 13:29:18 CEST 2015

wm4 <nfxjfg <at> googlemail.com> writes:

> > As said, I had no objections against your patch (on 
> > the contrary) but I wonder why you want to set a field 
> > that is mostly useful when using libswscale if you 
> > don't use libswscale.
> Uh, what?
> Do you think libswscale is the only thing that 
> processes video?

No, but it seemed to me that this is what your commit 
message implied.

> > > What is your opinion about this?
> > 
> > I committed part of the change making gray full range...
> > 
> > Whoever wants to use frame->data[0] should use it
> What do you even mean?

I thought your question was "Do you agree that gray 
should be full-range?" Some people need the yuv -> 
gray conversion not to change the values, and I 
always wonder why they call libswscale in the 
beginning, instead of simply using the Y plane.

> So what is the API user supposed to do? Special-case 
> by codec? Just what is it?

How is this codec-related / when is gray not full-scale 
(and FFmpeg can know it)?

Carl Eugen

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