[FFmpeg-devel] [RFC]Don't use round when encoding png

wm4 nfxjfg at googlemail.com
Sun Mar 1 21:34:46 CET 2015


On Sun, 1 Mar 2015 20:34:57 +0100
Michael Niedermayer <michaelni at gmx.at> wrote:

> On Sun, Mar 01, 2015 at 07:57:56PM +0100, wm4 wrote:
> > On Sun, 1 Mar 2015 19:48:20 +0100
> > Nicolas George <george at nsup.org> wrote:
> > 
> > > Le primidi 11 ventôse, an CCXXIII, wm4 a écrit :
> > > > I prefer the color of fuck broken platforms nobody uses.
> > > 
> > > Well, obviously someone uses a platform where it makes a difference,
> > > otherwise nobody would have noticed.
> > > 
> > > Regards,
> > > 
> > 
> > If they really care, get them to fix the platform (as long as our use
> > of the function is actually guaranteed by the standard).
> 
> the reason why it fails is probably that the code in pngenc.c tries
> to write a double precission value by using AV_W* macros
> 
> this is a bad idea and likely not what the author intended
> 

(Maybe then it shouldn't have been merged without review and without
presence on the mailing list?)

I'm pretty sure the author expected the values to be correctly rounded,
and that the AV_WB32() macro casts its float argument to an integer. Is
that not the case?


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