Am Mo., 15. Sept. 2025 um 17:49 Uhr schrieb Michel Dänzer <michel.daen...@mailbox.org>: > > On 15.09.25 17:37, Derek Foreman wrote: > > On 9/15/25 5:01 AM, Michel Dänzer wrote: > >> On 12.09.25 15:45, Derek Foreman wrote: > >>> On 9/12/25 2:33 AM, Chuanyu Tseng wrote: > >>>> Introduce a DRM interface for DRM clients to further restrict the > >>>> VRR Range within the panel supported VRR range on a per-commit > >>>> basis. > >>>> > >>>> The goal is to give DRM client the ability to do frame-doubling/ > >>>> ramping themselves, or to set lower static refresh rates for power > >>>> savings. > >>> I'm interested in limiting the range of VRR to enable HDMI's > >>> QMS/CinemaVRR features - ie: switching to a fixed rate for media playback > >>> without incurring screen blackouts/resyncs/"bonks" during the switch. > >>> > >>> I could see using an interface such as this to do the frame rate > >>> limiting, by setting the lower and upper bounds both to a media file's > >>> framerate. However for that use case it's not precise enough, as video > >>> may have a rate like 23.9760239... FPS. > >>> > >>> Would it be better to expose the limits as a numerator/denominator pair > >>> so a rate can be something like 24000/1001fps? > >> I was thinking the properties could allow directly specifying the minimum > >> and maximum number of total scanlines per refresh cycle, based on the > >> assumption the driver needs to program something along those lines. > > > > Surprisingly, this would also not be precise enough for exact media > > playback, as the exact intended framerate might not result in an integer > > number of scan lines. When that happens a QMS/CinemaVRR capable HDMI source > > is expected to periodically post a frame with a single extra scan line to > > minimize the error. > > Interesting, maybe your suggestion of numerator / denominator properties is > better then. API wise, I'd much prefer just using nanoseconds instead of two properties that compositors will in practice just use the same way.
> -- > Earthling Michel Dänzer \ GNOME / Xwayland / Mesa developer > https://redhat.com \ Libre software enthusiast
