Re: [PATCH 25/25] drm/armada: add iturbt_709 plane property to control YUV colorspace - Russell King

From: Russell King - ARM Linux <linux@armlinux.org.uk>
To: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: David Airlie <airlied@linux.ie>,
	dri-devel <dri-devel@lists.freedesktop.org>
Subject: Re: [PATCH 25/25] drm/armada: add iturbt_709 plane property to control YUV colorspace
Date: Mon, 1 Jan 2018 12:17:35 +0000	[thread overview]
Message-ID: <20180101121735.GA28752@n2100.armlinux.org.uk> (raw)
In-Reply-To: <20171213162214.GY10981@intel.com>

On Wed, Dec 13, 2017 at 06:22:14PM +0200, Ville Syrjälä wrote:
> On Wed, Dec 13, 2017 at 11:12:18AM -0500, Ilia Mirkin wrote:
> > On Wed, Dec 13, 2017 at 10:41 AM, Daniel Stone <daniel@fooishbar.org> wrote:
> > > Hi Russell,
> > >
> > > On 8 December 2017 at 12:31, Russell King <rmk+kernel@armlinux.org.uk> wrote:
> > >> Add the defacto-standard "iturbt_709" property to the overlay plane to
> > >> control the YUV to RGB colorspace conversion.  This is mutually
> > >> exclusive with the CSC_YUV CRTC property - the last property to be set
> > >> determines the resulting colorspace conversion.
> > >
> > > I haven't seen this in other drivers - is it a 'defacto standard'? I
> > 
> > xf86-video-nv supported it, and I added it to nouveau as well when I
> > ported YUV plane support. Some video players use the Xv property when
> > available.
> > 
> > https://cgit.freedesktop.org/xorg/driver/xf86-video-nv/tree/src/nv_video.c#n128
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpu/drm/nouveau/dispnv04/overlay.c?h=v4.15-rc3#n316
> 
>    {XvSettable | XvGettable, 0, 1, "XV_ITURBT_709"}
> 
> Who came up with that and when? XV_COLORSPACE was the one semi-standard
> I know of.

I've no idea, and I was hoping that someone else would know - my use of
it comes from research into what will make userspace work, not what
standards may say.

XV_ITURBT_709 is already in-use in distro standard userspace programs:

# grep XV_ITURBT_709 /usr/lib/vlc/plugins/ -r
Binary file /usr/lib/vlc/plugins/video_output/libxcb_xv_plugin.so matches
# grep XV_ITURBT_709 /usr/lib/gstreamer-1.0/ -r
Binary file /usr/lib/gstreamer-1.0/libgstxvimagesink.so matches

but not XV_COLORSPACE:

# grep XV_COLORSPACE /usr/lib/vlc/plugins/ -r
# grep XV_COLORSPACE /usr/lib/gstreamer-1.0/ -r

So while XV_COLORSPACE may be some kind of standard, it seems that
userspace has decided otherwise to go with a different name for this
control.

Anyway, I'll drop this patch and send a pull request for the remainder
to David.

-- 
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