[Bug 94820] Nearest neighbor scaling?

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Tue Apr 5 13:35:16 UTC 2016


--- Comment #5 from Alex Deucher <alexdeucher at gmail.com> ---
(In reply to nw9165-3201 from comment #4)
> (In reply to Michel Dänzer from comment #3)
> > Grigori, see the patch and discussion on bug 94816.
> Why are you pointing him to the xrandr patch?
> I think Grigori means something else.
> With the xrandr patch, the scaling happens in software, right?

It's done on the 3D engine.

> What Grigori most likely means is, that AMD GPUs/APUs most probably have a
> dedicated hardware scaler in their GPU which could be used for image scaling
> instead of xrandr?
> I'm fairly sure the GPU must have a dedicated hardware scaler, otherwise it
> could not scale up the image on POST.
> AMD GPUs even default to underscan on POST (on a lot of displays), so there
> must be a hardware scaler in use/available.
> In his case this hardware scaler seems to be using a bicubic filter.
> What he (and me) would like to know is how one could tell the hardware
> scaler to use nearest neighbor filtering instead of bicubic/bilinear
> filtering.
> Or does xrandr actually utilize the dedicated hardware scaler inside the GPU?

The randr scale options use the 3D engine.  Picking a non-native mode to
display on the panel uses either the scaler in the monitor (default for
external monitors) or the scaler on the GPU's display controller (default for
fixed laptop panels).

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