[Q] Is input lag has low as we can?

[mirh]

Follows the initially v-sync focused only brain-storm session post. <<==IMPORTANT
Now, putting aside stuttering, I'm wondering if those techniques couldn't be used.. to lower input lag on the other hand?

The availability situation of the various swap chains.. Is terrible.
Though, I guess conditionals for DXGI_SWAP_EFFECT_FLIP_SEQUENTIAL or D3DSWAPEFFECT_FLIPEX not to crash on different OSs could do miracles :p
sample1

What about poor GL, you'll ask me then? Microsoft is too selfish to reserve it a fast track too (even though for some reason this not-so-seemingly-dumb guy claims otherwise)
Well, surprise: say hello to NV_DX_interop extension, which leads us back to the previous case.
sample2 Seems like nvidia/intel/amd all have hacks in their driver to trigger flip/exclusive mode
Aside of helping with avoiding BitBlt, could this also use as a stop-gap measure to use DX shaders with GL renderer #1795?

Last but not least, I changed PFD_DOUBLEBUFFER to PFD_DOUBLEBUFFER_DONTCARE and W-T-F, borderless fullscreen is not exclusive anymore on AMD (#1437 (comment))
EDIT: seems normal

@turtleli we are all lovingly waiting from you 😘

[turtleli]

I have no idea about what you're trying to say. I don't think I could help even if I did.

[mirh]

https://msdn.microsoft.com/en-us/library/windows/desktop/hh706346.aspx

[willkuer]

I think he rather asks for an avih-style presentation of the problem/solution:

1. The following issue is present in pcsx2
2. I can trigger the issue by doing...
3. I expect instead that and that to happen.

It appears you like a lot of fill words and a very casual style of writing which seems to confuse some people as you are not drinking a coffee while chatting with somebody but opened an issue. I guess your wishes will be more easily fulfilled if you report the issue as an issue instead.

[gregory38]

Is it really an issue ? I mean 1920x1280x4 ~ 10 MB. GPU bandwidth is 100GB/s. So the copy is around 0.1 ms or 0.6% of the rendering time (60 fps target).

[mirh]

Let's say that it would be easier to report the issue as such if it was one in the first place.
Instead this was more consultative rather than anything. Forums might have been better probably, but.. I guess I prefer github chattiness?
Anyway, first of all, an OS: Windows tag would feel appropriate.
Second: 95% of times pcsx2 is ran through DWM. As you can see in the scheme above, this incurs in an extra buffer copy.
My assumption was that could be adding (non-insignificant) extra input latency to the image.

Indeed, I don't know for sure, and gregory may as well be right.
Or perhaps he's thinking too much linux-simplistically and it's not (see here).
It should be easily testable on W10 (without the need of special hardware) with PresentMon then.

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And that was a thing.
The other was underlining that even though Microsoft didn't lay out a bed of roses for GL, that could still benefit of the discovery with the interop trick.
Which possibly in my ignorance of how post-process shaders work, could also put us on the fast track to nicely solve latest #1795 quibble.
EDIT: or maybe just add latency?

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Last, but not least... I found that crazy thing about AMD (I didn't want to clutter further the other thread)
Which thinking better has nothing to do with the title of this... I'll change it then .-.

p.s. I have now this hypothesis nvidia and amd (¿intel?) all have this weird behavior with fullscreen opengl, because.. they cannot have variable refresh rate working with borderless windows otherwise?

[mirh]

Ok, I got to talk with some quite knowledgeable Windows person and it seems that, waitable swapchains aside, compared to best case scenario bitblt incurs in a latency penalty more on the neighborhood of gregory's guess than whatever else.
So I guess I can close this.

EDIT: https://blogs.msdn.microsoft.com/directx/2018/04/09/dxgi-flip-model/ 🤔🤔