Improvements to VRR below-the-range/low framerate compensation.

[Michel Dänzer]

On 2019-04-18 5:51 a.m., Mario Kleiner wrote:
> 
> My desired application of VRR for neuroscience/vision research
> is to control the timing of when frames show up onscreen, e.g.,
> to show animations at different "unconventional" framerates,
> so i'm mostly interested in how well one can control the timing
> between successive OpenGL bufferswaps. This is a bit different
> from what a game wants to get out of VRR, probably closer to
> what a movie player might want to do.

As discussed before, I expect that games which care about smooth
animation will want to control the presentation time as well in the long
run, so that they can make the presentation time match the simulation
time corresponding to the frame contents.

There is already support for specifying the target presentation time in
(at least, there might be more I'm not aware of) VDPAU, the Vulkan
VK_GOOGLE_display_timing extension, and the X11 Present extension
protocol (not actually implemented yet in xserver though).

Ideally, this should also be available in the kernel UAPI. That should
allow hitting the target more accurately / reliably, and might also
allow making better use of compensation mechanisms such as those touched
by this series, since userspace can call into the kernel ahead of the
target time, giving the kernel an opportunity to make adjustments earlier.

Since you have a strong use-case for this functionality, maybe you'd be
interested in working on it?


-- 
Earthling Michel Dänzer               |              https://www.amd.com
Libre software enthusiast             |             Mesa and X developer