[RFC 0/5] Introduce drm sharpening property

[Pekka Paalanen]

On Tue, 12 Mar 2024 08:30:34 +0000
"Garg, Nemesa" <nemesa.garg at intel.com> wrote:

> This  KMS property is not implementing any formula

Sure it is. Maybe Intel just does not want to tell what the algorithm
is, or maybe it's even patented.

> and the values
> that are being used are based on empirical analysis and certain
> experiments done on the hardware. These values are fixed and is not
> expected to change and this can change from vendor to vendor. The
> client can choose any sharpness value on the scale and on the basis
> of it the sharpness will be set. The sharpness effect can be changed
> from content to content and from display to display so user needs to
> adjust the optimum intensity value so as to get good experience on
> the screen.
> 

IOW, it's an opaque box operation, and there is no way to reproduce its
results without the specific Intel hardware. Definitely no way to
reproduce its results in free open source software alone.

Such opaque box operations can only occur after KMS blending, at the
CRTC or later stage. They cannot appear before blending, not in the new
KMS color pipeline design at least. The reason is that the modern way
to use KMS planes is opportunistic composition off-loading.
Opportunistic means that userspace decides from time to time whether it
composes the final picture using KMS or some other rendering method
(usually GPU and shaders). Since userspace will arbitrarily switch
between KMS and render composition, both must result in the exact same
image, or end users will observe unwanted flicker.

Such opaque box operations are fine after blending, because there they
can be configured once and remain on forever. No switching, no flicker.

Where does "sharpeness" operation occur in the Intel color processing
chain? Is it before or after blending?

What kind of transfer characteristics does it expect from the image,
and can those be realized with KMS CRTC properties if KMS is configured
such that the blending happens using some other characteristics (e.g.
blending in optical space)?

What about SDR vs. HDR imagery?


Thanks,
pq

> > -----Original Message-----
> > From: dri-devel <dri-devel-bounces at lists.freedesktop.org> On Behalf Of Simon
> > Ser
> > Sent: Monday, March 4, 2024 7:46 PM
> > To: Garg, Nemesa <nemesa.garg at intel.com>
> > Cc: Pekka Paalanen <pekka.paalanen at haloniitty.fi>; intel-
> > gfx at lists.freedesktop.org; dri-devel at lists.freedesktop.org; G M, Adarsh
> > <adarsh.g.m at intel.com>
> > Subject: RE: [RFC 0/5] Introduce drm sharpening property
> > 
> > On Monday, March 4th, 2024 at 15:04, Garg, Nemesa <nemesa.garg at intel.com>
> > wrote:
> >   
> > > This is generic as sharpness effect is applied post blending.
> > > Depending on the color gamut, pixel format and other inputs the image
> > > gets blended and once we get blended output it can be sharpened based
> > > on strength value provided by the user.  
> > 
> > It would really help if you could provide the exact mathematical formula applied
> > by this KMS property.  

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