Re: [FFmpeg-devel] Again pre-multiplied alpha

[Niklas Haas <ffmpeg@haasn.xyz>]

On Wed, 23 Jul 2025 16:11:45 +0200 Nicolas George <george@nsup.org> wrote:
> Niklas Haas (HE12025-07-23):
> > Changes since v1:
> > - Correctly implement alpha mode tagging for JPEG XL
> > - Set correct alpha mode for OpenEXR (which is always premultiplied)
> > - Ensure -alpha_mode specified on the command line correctly propagates
> > - Print out a warning when overriding the alpha mode explicitly
> >
> > Includes an unrelated fix for -chroma_sample_location also being ignored,
> > since the fix for that was adjacent to the fix for the alpha mode field.
> >
> > Submitting this for re-evaluation. I decided in the end not to include full
> > negotiation for the alpha mode, primarily because there is no filter currently
> > existing that only handles one or the other.
>
> Also, negotiation is fragile and needs tests.
>
> But can you point to where the code that prevents a component not
> ready from receiving a premultiplied frame is?

[PATCH v2 05/18] avcodec/encode: enforce alpha mode compatibility at encode time

>
> Regards,
>
> --
>   Nicolas George
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