On 2018-10-05 7:48 p.m., Kazlauskas, Nicholas wrote: > On 10/05/2018 12:56 PM, Michel Dänzer wrote: >> On 2018-10-05 6:21 p.m., Kazlauskas, Nicholas wrote: >>> On 10/05/2018 04:10 AM, Pekka Paalanen wrote: >>>> >>>> I also believe that it would be useful to expose vmin/vmax to userspace >>>> as properties, so that display servers and apps can plan ahead on when >>>> they will render. I suppose that can be left for later when someone >>>> starts working on userspace taking advantage of it, so that the proper >>>> userspace requirement for new UABI is fulfilled. >>> >>> Knowing the vmin/vmax could potentially be useful for testing but most >>> applications shouldn't be trying to predict or adjust rendering based on >>> these. >> >> FWIW, recent research indicates that this is necessary for perfectly >> smooth animation without micro-stuttering, even with VRR. > > This was brought up in previous RFCs about this but I'm not really > convinced by the research methodology and the results from those threads. > > Targeting the max vrefresh of the display (which is known without > additional properties) should be best for prediction since anything > lower would be inherently less smooth by definition. Smooth animation isn't only about frame-rate, it's also about the timing of each frame's presentation and its contents being consistent with each other[0]. To ensure this, the application has to know the constraints for when the next frame can be presented, and it has to be able to control when the frame is presented. [0] One example of this is https://www.youtube.com/watch?v=V4fgYS38aQg . When this video is played back at 60 fps, the upper sphere moves smoothly, but the lower sphere sometimes jumps back and forth slightly (it's pretty subtle, might take a while to notice), because its position isn't always consistent with the frame's presentation timing. -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
