Adding dri-devel, which I should've included from the start. On 2018-04-09 03:56 PM, Harry Wentland wrote: > === What is adaptive sync and VRR? === > > Adaptive sync has been part of the DisplayPort spec for a while now and allows graphics adapters to drive displays with varying frame timings. VRR (variable refresh rate) is essentially the same, but defined for HDMI. > > > > === Why allow variable frame timings? === > > Variable render times don't align with fixed refresh rates, leading to > stuttering, tearing, and/or input lag. > > e.g. (rc = render completion, dr = display refresh) > > rc B C D E F > dr A B C C D E F > > ^ ^ > frame missed > repeated display > twice refresh > > > > === Other use cases of adaptive sync ==== > > Beside the variable render case, adaptive sync also allows adjustment of refresh rates without a mode change. One such use case would be 24 Hz video. > > > > === A DRM render API to support variable refresh rates === > > In order to benefit from adaptive sync and VRR userland needs a way to let us know whether to vary frame timings or to target a different frame time. These can be provided as atomic properties on a CRTC: > * bool variable_refresh_compatible > * int target_frame_duration_ns (nanosecond frame duration) > > This gives us the following cases: > > variable_refresh_compatible = 0, target_frame_duration_ns = 0 > * drive monitor at timing's normal refresh rate > > variable_refresh_compatible = 1, target_frame_duration_ns = 0 > * send new frame to monitor as soon as it's available, if within min/max of monitor's reported capabilities > > variable_refresh_compatible = 0/1, target_frame_duration_ns = > 0 > * send new frame to monitor with the specified target_frame_duration_ns > > When a target_frame_duration_ns or variable_refresh_compatible cannot be supported the atomic check will reject the commit. > > > > === Previous discussions === > > https://lists.freedesktop.org/archives/dri-devel/2017-October/155207.html > > > > === Feedback and moving forward === > > I'm hoping to get some feedback on this or continue the discussion on how adaptive sync / VRR might look like in the DRM ecosystem. Once there are no major concerns or objections left we'll probably start creating some patches to sketch this out a bit better and see how it looks in practice. > > > > Cheers, > Harry > _______________________________________________ > amd-gfx mailing list > amd-gfx@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/amd-gfx > _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
