[Bug 94820] Nearest neighbor scaling?

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=94820

--- Comment #8 from nw9165-3201 at yahoo.com ---
(In reply to Alex Deucher from comment #7)
> I'm not sure what algorithm(s) the display scaler uses or can use off hand. 
> We just use whatever the default is.

Hi Alex, thanks again for the swift reply, much appreciated :).

Well, could you please please find out what algorithms the display scaler uses
or can use?

I have always been very interested in this. The scaler on the GPU's display
controller is a bit mysterious, because there is not much information available
on this topic at all. It would be really nice if you could bring some light
into this.

Actually, in the Xbox 360 era, there was some talk about the scaler inside the
Xbox 360 (AMD GPU). It's documented in the following thread on the Beyond3D
forum, see:

https://forum.beyond3d.com/threads/list-of-rendering-resolutions.41152/

> 360
>
> Xenos is the hardware scaler, not HANA/ANA, which are just the video
> output chips dealing with digital/analog output to the various
> connections made with the display. Dave Baumann
>
> AVIVO takes more samples for scaling so it is expected that the
> scaling is better [strike](the algorithm also appears to be
> some form of bicubic, not a simple bilinear)[/strike]
> Update: see below
>
> Hardware scaling to the output resolution chosen in the dashboard is
> [strike]automagically performed[/strike] :?:.
>
> In upscaling to 1080p, some games may first scale to 720p in software
> before the GPU scales to a 1080p output. e.g. RR6, SCIV, VF5,
> CoD4, H3, TR:L...
>
> Some games let the GPU handle the scaling to 1080p directly
> from the arbitrary resolution. e.g. MotoGP 06, PGR3, ESIV:O...
>
> "lanczos is just one of the selectable filters. Ultimately each game
> 'could' opt to use a different filter/sample count combination
> (though I suspect most don't bother)." -Fafalada

So, as you can see, there was even a mention that the algorithm (filter) could
be changed from Bicubic to Lanczos and so on...

Now it would be interesting to know if all AMD GPUs have this capability and
how it can be utilized.

And does the scaler on the GPU's display controller have a dedicated name? In
the talk above it seems to be referred to as "AVIVO"?

Also, it would be nice if you could clarify if AMD's VSR (Virtual Super
Resolution) is performed on the scaler on the GPU's display controller or if it
is performed elsewhere.

Again, would be really nice if you could clarify all those things, the AMD GPUs
have a hardware scaler that is sitting there, but nothing is really known about
it, which is unfortunate.

Regards

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