RFC for a render API to support adaptive sync and VRR

[Daniel Vetter]

On Wed, Apr 18, 2018 at 5:58 AM, Keith Packard <keithp at keithp.com> wrote:
> Michel Dänzer <michel at daenzer.net> writes:
>> Time-based presentation seems to be the right approach for preventing
>> micro-stutter in games as well, Croteam developers have been researching
>> this.
>
> Both the Vulkan GOOGLE_display_timing extension and X11 Present
> extension offer the ability to specify the desired display time in
> seconds.
>
> Similarly, I'd suggest that the min/max display refresh rate values be
> advertised as time between frames rather than frames per second.
>
> I'd also encourage using a single unit for all of these values,
> preferably nanoseconds. Absolute times should all be referenced to
> CLOCK_MONOTONIC.

+1 on everything Keith said. I got somehow dragged in khr vk
discussions around preventing micro-stuttering, and consensus seems to
be that timestamps for scheduling frames is the way to go, most likely
absolute ones (not everything is running Linux unfortunately, so can't
go outright and claim it's guaranteed to be CLOCK_MONOTONIC).
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch