Freesync better than gsync?

Talk about AMD's FreeSync and VESA AdaptiveSync, which are variable refresh rate technologies. They also eliminate stutters, and eliminate tearing. List of FreeSync Monitors.
Edmond

Freesync better than gsync?

Post by Edmond » 30 Jun 2014, 04:51

Watch this interview (the following 4-5 mins starting @ ~1h1min)

http://youtu.be/fZGV5z8YFM8?t=1h1m


TL;DW:

Gsync buffers each frame trough 700mbs of memory that comes with it.
-This always adds 1 frame of latency.
-And also thats why it costs so much to implement.
-Freesync doesnt poll the monitor, so the same amount of lag as vsync off. (Also, probably doest have that side effect when you output framerate close to max refresh - where gsync starts giving lag like vsync?)


Personal opinon: even if these were all lies, not jumping on any trains yet, will wait for freesync prototypes in october to see whats what.

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omgBlur
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Re: Freesync better than gsync?

Post by omgBlur » 30 Jun 2014, 08:14

This is an interesting video.


But as you mentioned since none of this is concrete, those that are interested in a variable refresh-rate monitor should hold it out another year or so for both monitor types to be out. We are going to start receiving a mass release of G-Sync enabled monitors in the next few months and a better prototype of the FreeSync.

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RealNC
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Re: Freesync better than gsync?

Post by RealNC » 30 Jun 2014, 11:04

Edmond wrote:Gsync buffers each frame trough 700mbs of memory that comes with it.
-This always adds 1 frame of latency.
G-Sync input lag was tested and was shown to be less than one frame:

http://www.blurbusters.com/gsync/preview2/

In the Crysis test, at 47FPS you have a frame latency of 21.28ms. The average input latency with vsync off was 54ms ((53+55) / 2). The average input latency with gsync on was 55.5ms ((59+52) / 2). Additionally, gsync on resulted in going from 47FPS to 45FPS, raising the frame latency a little bit (22.22ms). Now, if gsync was adding one frame of latency, the result would not have been 55.5ms, but 77.72ms (55.5 + 22.22).

So the claim of G-Sync adding 1 frame of latency seems to be false. Unless there was a fault in the test.

However, it could be that what was really meant and not explained (in order to make a bigger impact with that statement) is that "frame" here refers to one monitor refresh cycle, not a GPU frame. In that case, G-Sync on a 144Hz monitor would add a 6.94ms of latency. Which is not much, but still significant to certain users. However, on a 60Hz G-Sync monitor, this would mean 16.67ms latency, which is too much.

I guess further tests are needed to determine whether this is true or not.

Edmond wrote:Also, probably doest have that side effect when you output framerate close to max refresh - where gsync starts giving lag like vsync?
If the game outputs frames at a faster rate than the monitor can display, the game has to wait. There can be no way around that.

The other alternative is to send the frames anyway, in which case you would get the usual tearing, as you do now with V-Sync off.
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Edmond

Re: Freesync better than gsync?

Post by Edmond » 01 Jul 2014, 03:03

RealNC wrote: If the game outputs frames at a faster rate than the monitor can display, the game has to wait. There can be no way around that.

The other alternative is to send the frames anyway, in which case you would get the usual tearing, as you do now with V-Sync off.
What if the video card knows the min and max refresh rates of the monitor? And understands that there is no need to make more than 144 or 60 frames? Like, it doesnt have to work just by the monitor adjusting to the video card, it can work both ways, no?

I might not be understanding this correctly but i thought that lag at max+ frames happens cuz there are more frames made than place to put them. Hence we use that global 59fps cap to remove vsync lag by manually limiting the video card, since it has no clue of its own.

Either way, ill see the freesync prototypes first before i worry about which monitor to have.

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Re: Freesync better than gsync?

Post by RealNC » 01 Jul 2014, 06:54

Edmond wrote:
RealNC wrote: If the game outputs frames at a faster rate than the monitor can display, the game has to wait. There can be no way around that.
What if the video card knows the min and max refresh rates of the monitor? And understands that there is no need to make more than 144 or 60 frames? Like, it doesnt have to work just by the monitor adjusting to the video card, it can work both ways, no?
The video card can't do much about it. It's the game's engine itself that needs to deal with this. Note the "input" in the term "input lag". The video card doesn't deal with input from keyboard, mouse, gamepad, etc. If the game engine reads input too soon and buffers those inputs for several frames, and then the video card stalls in order to match the monitor's output rate, you get input lag because the game's buffers pile up instead of getting flushed right away and sent to the GPU. There's really no way around that.

And the GPU actually rendering naturally at a specific framerate rather than as fast as possible isn't possible with current technology. The GPU cannot know how long it's going to take to render a frame. That information would be required to have a natural frame limit. Since that's not possible, the GPU just renders the frame, and if the rendering was too fast, it needs to wait for the monitor. However, Mark Rejhon ("Chief") proposed an alternative way for the GPU driver to pace the frame rate. I'm sure he'll pop-in here and explain once more :-)
I might not be understanding this correctly but i thought that lag at max+ frames happens cuz there are more frames made than place to put them. Hence we use that global 59fps cap to remove vsync lag by manually limiting the video card, since it has no clue of its own.
The 59FPS cap reduces input lag because it forces the game engine to flush its buffers instead of piling them up when waiting for the monitor. That's all there is to it, really :-) And it's also why engine-internal frame cappers can work way better than external ones. The external frame capper introduces the delay *after* the game has read input. An internal frame capper can instead do the delay before reading input. The video card having a clue or not is not really relevant in this regard; it cannot affect the game's internal decision of when to read input from the user.

Edit:
In any event, the above is my understanding of the issue. I could be wrong, mind you :mrgreen:
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flood
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Re: Freesync better than gsync?

Post by flood » 01 Jul 2014, 23:59

i doubt that gsync adds lag when fps is under the max supported by display

but it does seem to have one more frame of lag than necessary when fps is limited by display

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Re: Freesync better than gsync?

Post by Sparky » 02 Jul 2014, 15:32

flood wrote:i doubt that gsync adds lag when fps is under the max supported by display

but it does seem to have one more frame of lag than necessary when fps is limited by display
When you're limited by the display, the only way to get rid of that lag is to disable v-sync(including freesync and g-sync) or cap framerate in game.

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Re: Freesync better than gsync?

Post by applejack » 29 Jul 2014, 18:54

concerning AMD / Richard Huddy's claim that G-Sync always adds 1 frame of latency for buffering (obviously false), here's the official Nvidia response to that (29:48)

https://www.youtube.com/watch?v=aG2kIUe ... 6_w#t=1788

^ they also refer to potential issues or not-that-good of an experience for the so called Freesync, but we'll see...

to me it smells like the same old ATI/AMD blame & promise game, followed by underwhelming execution.
they might surprise but I've lost interest in their products many years ago (and up to this day) anyway :ugeek:

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Re: Freesync better than gsync?

Post by IwantGSYNC » 10 Aug 2014, 10:05

@applejack
Interesting interview, thank you!

Also, here is what AMD FAQ says:
http://support.amd.com/en-us/search/faq/220
There are three key advantages Project FreeSync holds over G-Sync: no licensing fees for adoption, no expensive or proprietary hardware modules, and no communication overhead.
The last benefit is essential to gamers, as Project FreeSync does not need to poll or wait on the display in order to determine when it’s safe to send the next frame to the monitor.
http://support.amd.com/en-us/search/faq/224
An AMD Radeon™ graphics card compatible with Project FreeSync uses the DisplayPort™ Adaptive-Sync specification to automatically determine the minimum and maximum refresh rates supported by a dynamic refresh-ready system. Using this approach, no communication must occur to negotiate the time a current frame remains on-screen, or to determine that is safe to send a new frame to the monitor.

By eliminating the need for ongoing communication with pre-negotiated screen update rates, Project FreeSync can execute highly dynamic changes in frame presentation intervals without incurring communications overhead or latency penalties.

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Re: Freesync better than gsync?

Post by RealNC » 10 Aug 2014, 14:57

I'll believe it when I see it. Which means maybe in a year or more. :-)

Right now, Freesync has exactly *zero* advantages over Gsync. Because it doesn't exist. It's vaporware.
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