Re: [RFC] Plane color pipeline KMS uAPI

From: Melissa Wen <mwen@igalia.com>
To: Pekka Paalanen <ppaalanen@gmail.com>
Cc: "xaver.hugl@gmail.com" <xaver.hugl@gmail.com>,
	"DRI Development" <dri-devel@lists.freedesktop.org>,
	wayland-devel <wayland-devel@lists.freedesktop.org>,
	"Victoria Brekenfeld" <victoria@system76.com>,
	"Jonas Ådahl" <jadahl@redhat.com>,
	"Uma Shankar" <uma.shankar@intel.com>,
	"Joshua Ashton" <joshua@froggi.es>,
	"Michel Dänzer" <mdaenzer@redhat.com>,
	"Aleix Pol" <aleixpol@kde.org>,
	"Sebastian Wick" <sebastian.wick@redhat.com>
Subject: Re: [RFC] Plane color pipeline KMS uAPI
Date: Tue, 9 May 2023 16:01:02 -0100	[thread overview]
Message-ID: <20230509170102.d2iec32gxn5lur72@mail.igalia.com> (raw)
In-Reply-To: <20230509144717.7c85443d@eldfell>

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On 05/09, Pekka Paalanen wrote:
> On Tue, 9 May 2023 10:23:49 -0100
> Melissa Wen <mwen@igalia.com> wrote:
> 
> > On 05/05, Joshua Ashton wrote:
> > > Some corrections and replies inline.
> > > 
> > > On Fri, 5 May 2023 at 12:42, Pekka Paalanen <ppaalanen@gmail.com> wrote:  
> > > >
> > > > On Thu, 04 May 2023 15:22:59 +0000
> > > > Simon Ser <contact@emersion.fr> wrote:
> > > >  
> 
> ...
> 
> > > > >     Color operation 47 (3D LUT RAM)
> > > > >     └─ "lut_data" = Gamut mapping + tone mapping + night mode
> > > > >     Color operation 48 (blend gamma)
> > > > >     └─ "1d_curve_type" = PQ  
> > > 
> > > ^
> > > This is wrong, this should be Display Native -> Linearized Display Referred  
> > 
> > This is a good point to discuss. I understand for the HDR10 case that we
> > are just setting an enumerated TF (that is PQ for this case - correct me
> > if I got it wrong) but, unlike when we use a user-LUT, we don't know
> > from the API that this enumerated TF value with an empty LUT is used for
> > linearizing/degamma. Perhaps this could come as a pair? Any idea?
> 
> PQ curve is an EOTF, so it's always from electrical to optical.
> 
> Are you asking for something like
> 
> "1d_curve_type" = "PQ EOTF"
> 
> vs.
> 
> "1d_curve_type" = "inverse PQ EOTF"?
> 
> I think that's how it should work. It's not a given that if a
> hardware block can do a curve, it can also do its inverse. They need to
> be advertised explicitly.

Sounds good and clear to me.

Thanks!

Melissa

> 
> 
> Thanks,
> pq
> 
> ps. I picked my nick in the 90s. Any resemblance to Perceptual
> Quantizer is unintended. ;-)

:D

> 
> 
> > > >
> > > > You cannot do a TF with a matrix, and a gamut remap with a matrix on
> > > > electrical values is certainly surprising, so the example here is a
> > > > bit odd, but I don't think that hurts the intention of demonstration.  
> > > 
> > > I have done some corrections inline.
> > > 
> > > You can see our fully correct color pipeline here:
> > > https://raw.githubusercontent.com/ValveSoftware/gamescope/master/src/docs/Steam%20Deck%20Display%20Pipeline.png
> > > 
> > > Please let me know if you have any more questions about our color pipeline.

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