[FFmpeg-devel] avfilter/vf_premultiply : use full range for RGB input

[Hendrik Leppkes]

On Sun, Mar 18, 2018 at 9:26 AM, wm4 <nfxjfg at googlemail.com> wrote:
> On Sat, 17 Mar 2018 20:46:50 +0100
> Martin Vignali <martin.vignali at gmail.com> wrote:
>
>> Hello,
>>
>> Patch in attach change premultiply/unpremultiply filter for RGB input
>> to process it at full range
>>
>> Avoid very strange result in unpremultiply mode
>>
>> To test :
>> ./ffmpeg -i ./fate-suite/mov/mov_alpha_premult.mov -vf
>> unpremultiply=inplace=1 resStraight.png -y
>>
>> ./ffmpeg -i ./fate-suite/mov/mov_alpha_premult.mov -vf
>> format=gbrap16,unpremultiply=inplace=1 resStraight16.png -y
>
> I thought all alpha in ffmpeg is "straight" (not premultiplied). Was I
> lied to?

If you pre-multiplty the alpha and then save it as a file, how it is
supposed to know that you did that? :)

-  Hendrik