Ubuntu's Mir May Be Ready For FreeSync / Adaptive-Sync

[phoronix]

Phoronix: Ubuntu's Mir May Be Ready For FreeSync / Adaptive-Sync

The Mir display server may already be ready for working with AMD's FreeSync or VESA's Adaptive-Sync, once all of the other pieces to the Linux graphics stack are ready...

http://www.phoronix.com/scan.php?page=news_item&px=Mir-FreeSync-AdaptiveSync

[pal666]

comment actually says there is no need to support it, it works without any support

[Dick Palmer]

comment actually says there is no need to support it, it works without any support

Um, that's exactly what Michael said... It's what "already" means: "The Mir display server may already be ready for working.."

[pal666]

Um, that's exactly what Michael said... It's what "already" means: "The Mir display server may already be ready for working.."

no, not what he said. not mir already working, instead freesync is working without any mir intervention

[dh04000]

In other news, "Earth Avoided Strike by an Asteroid Today". There was no asteroid to avoid, but we did avoid a strike by default.

[Zan Lynx]

I've never understood why there's a problem with this. If the software is already doing VSync then with Adaptive Sync, if your software is producing frames below the maximum display rate, the hardware is always ready for a new frame. If the software is above the maximum rate then the hardware waits for VSync.

The only tricky bits come from software that expects a consistent tick rate on display frames for games or multimedia. As far as I know, display managers are not one of these things.

Now after mentioning multimedia I realize there might be issues deciding when to switch frames if some of your display surfaces are using presentation timing at 24, others at 30, some at 50, and the output display is 120 Hz adaptive. Decisions have to be made.

[starshipeleven]

I've never understood why there's a problem with this. If the software is already doing VSync then with Adaptive Sync, if your software is producing frames below the maximum display rate, the hardware is always ready for a new frame. If the software is above the maximum rate then the hardware waits for VSync.

the issue here is that "the hardware is ready for a new frame" isn't true.
The screen has a fixed refresh rate, and if the system sends frames off sync (like the screen is at your average 60hz and the system is providing like 37 frames per second...) you are offloading this to the screen controller, that decides what to show and when, as it MUST flash the screen 60 times per second, and it can only decide to show the same frame multiple times or drop some frames to compensate and go with an even number.

This has limits and puts way too much smarts on a device that isn't terribly smart, and on loads where this matters (gaming, quite a few movies), it shows.

With Adaptive Sync or G-Sync the system simply tells the display controller, "look I have a stream coming at this framerate, plz change refresh rate", which avoids the whole decisions above alltogether and no weird shit happens as the controller is back to its dumb and simple duties.

Now after mentioning multimedia I realize there might be issues deciding when to switch frames if some of your display surfaces are using presentation timing at 24, others at 30, some at 50, and the output display is 120 Hz adaptive. Decisions have to be made.

When android didn't have this feature and you (potentially) had to change manually screen frequency each time you were switching film in your mediabox...

Consider that some media does not even have a fixed framerate (many streamings).

[starshipeleven]

stupid unapproved post above for Zan Lynx
should appear soonish.

[juno]

They do already have the xf86-video-amdgpu DDX change that's also needed.

I thought the ddx drivers should become extinct anyway!?
Why is this not in the modesetting driver? Intel said that they want to support Adaptive Sync in the future, too.
Although I appreciate the foss efforts, it's sad how long we have to wait for features that have worked on windows for a long time.

[Zan Lynx]

With Adaptive Sync or G-Sync the system simply tells the display controller, "look I have a stream coming at this framerate, plz change refresh rate", which avoids the whole decisions above alltogether and no weird shit happens as the controller is back to its dumb and simple duties.

Pretty sure that isn't how it works at all. Not with G-Sync anyway. Perhaps I just assumed Adaptive Sync was just as good. Maybe it isn't.

G-Sync just accepts the frame. If the display hardware has other problems with it the G-Sync hardware on the monitor smooths it away. The GPU / computer side never sees a problem.

That's why the output is smooth. It's smooth like running without V-Sync. The software side on the computer never never waits unless it has vsync enabled and hits the max FPS.