[Libva] [PATCH]: vdpau-driver: don't expect premultiplied alpha as subpicture data

[Holger Kaelberer]

Hi,

the attached patch changes blending behaviour for the vdpau-driver to classical alpha blending.

So far it expects premultiplied alpha. This is not in line with, at least, what intel-driver expects.

Why would one need this change? In lack of an implementation of vaSetSubpictureGlobalAlpha() in the 
libva-backend/vdpau-driver, the only way to implement fading in/out of subpictures/OSD-elements is 
to change alpha values per-pixel. That is already expensive and becomes even more expensive if you 
need to premultiply RGB values. And makes it almost impossible to implement such a feature if 
blending is handled differently by different libva-backends.

Please redirect me, if I should open a ticket for that.

Thanks for reviewing and considering this patch,
    Holger
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