I'm not sure if it's difficult or just few lines of code but in case it's quick fix it'd be nice to have 40 bit color (for Quadro) support, doesn't matter png (which supports 10bpc) or raw, whatever just anything to transport deep color. I happen to work in environment supporting 10bpc. If you care,
ATI FirePro support 12bpc? if i remember well. It's ofc supported by normal X server.
Neither Xvfb nor wiki/Xdummy support bpp higher than 24/32 at present. This is what you get with Xdummy:
[ 8081.079] (EE) DUMMY(0): Given depth (30) is not supported by this driver
And in the code we see:
if (!xf86SetDepthBpp(pScrn, 0, 0, 0, Support24bppFb | Support32bppFb))
So this driver would require some work (not sure how much) to support anything other than 24 / 32.
Until then, we could support such modes by running against a real X11 server instead of a virtual one, but this would limit us to one session per GPU at best...
As for the xpra code itself, the pixel compression would not be too much of a problem (I think vp9 supports 10bpp and even alpha channels) - though the client would require some work to take advantage of the extra colours depth.
Maybe we can add support for this using desktop mode (#1247), this would at least ensure that we can handle those pixels formats in both server and client code before we add support for it in Xvfb or the dummy driver.
AFAICT, even though png supports 48-bit colour, there is no support for it in pillow, see: Creating a 48-bit TIFF file in Python with PIL, so we will need another encoder even the simplest case..
30 bit support in Linux is still kind of poor, every app implementing it is small step forward. I still really hope this functionality can be implemented in xpra.
Also nVidia drivers support dithered 10bpc on 8bpc displays and it works really well so something like this would be extremely useful if implemented in xpra as it'd actually enable people without Quadro GPUs to display dithered 10bpc on any hardware, even Intel GPUs as long as host does have Quadro/FirePro? to launch X server in 30bit mode.
So host launches X server in 30 bit color, then xpra captures it, possibly performs 10->8 bit dithering and displays on client PC which can have some crappy consumer GPU. It'd be really awesome feature saving money for a lot of people because many of 2d artists are getting cards like Quadro or FirePro? just to get 30bit color and it's not cheap. In laptops Quadro cards are even more expensive as it's only offered in pure top-end mobile workstations.
Being able to get one professional card like this and then use its 30 bit capabilities on all PCs in home no matter what hardware they have would be simply killer feature for some artists.
See ticket:1260#comment:1 and Anandtech: NVidia Pascal - Display Matters: New Display Controller, HDR, & HEVC: For Pascal, NVIDIA is opening things up a bit more, but they are still going to keep the most important aspect of that feature differentiation in place. 10bit color is being enabled for fullscreen exclusive OpenGL applications – so your typical OpenGL game would be able to tap into deeper colors and HDR – however 10bit OpenGL windowed support is still limited to the Quadro cards. So professional users will still need Quadro cards for 10bit support in their common applications.
For enabling 30-bit output: How to Enable 30-bit color on Linux For verifying 30-bit output: 30-bit depth with Linux driver does not produce 30-bit output on monitor.
changes needed to xorg.conf for running in 30bpp mode
changes needed to dummy driver for supporting 30bpp mode
resize-display=no(randr is broken with this change and causes Xorg to crash hard)
simplest test config for 30 bpp with Xdummy
Running in 30-bit mode now only requires changing the
DefaultDepth 30 in the xorg.conf, or adding
-depth 30 to the xdummy command line.
@lapsio / rektide: does that work for you? (will continue improving this in future releases, see ticket links from comment:7)
See also: ticket:56#comment:22
Relevant talk: Linux and high dynamic range displays
Not heard back, closing.
Relevant X11 discussion: RFC: Visual Class for On-Screen HDR Drawables
As of r15028, the display's bit depth will be shown in the server output (here with 30-bit):
xpra X11 version 2.0-r15028 64-bit uid=1000 (antoine), gid=1000 (antoine) running with pid 22114 on Linux Fedora 25 TwentyFive connected to X11 display :10 with 30 bit colors
The client bit depth is now also displayed, see ticket:1309#comment:1
r15072 makes it possible to use jpeg and png by downsampling the original 30-bit image. That's only used if we have no other choice.
New wiki page and command line option to switch bit depth, see wiki/ImageDepth
Some minor fixes:
The dummy patch has been merged: PATCH: support for 30 bit depth in dummy driver
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/909