(I posted this on our local Fighting Game discussion forum, though figured it could be of use to people here.)
Those of you who know me perhaps know I'm the world's pickiest bitch when it comes to lag, both the online latency variety and also local input lag typically associated with screen post-processing and vsync. The latter especially.
I've found another method to reduce local input lag a little further in the game (SFIV on PC) while still enjoying the smoothness associated with vsync using the Borderless Gaming tool.
This application allows you to capture any* windowed application and force it to a maximised window sans edge borders. This allows any game to forego its own vsync implementation and instead fall back to Windows' own vsync (which is also triple buffered) that has extremely low input lag compared to 90% of full screened applications utilising DirectX or OpenGL.
So with SFIV, I run the game, specify 1080p as my game resolution, DISABLE vsync and accept the settings. Next, I hit ALT+Enter to force the game to a window. Then, I run Borderless Gaming, run the application scan, select SSFIVAE (the detected executable) and force it into the 'favourites' column. Then click the third icon down from the centre to force the game into a borderless window occupying the full screen.
This results in what passes for a full screened render, albeit with a much snappier vsync implementation and a reduction in input lag (for those who typically run the game with vsync enabled in the first place). Because you are now essentially running the game WITH vsync (borrowed from Windows' own desktop renderer) you have a smoother looking game free (mostly) of the accepted tearing and with massively reduced, if not non-existent input lag.
Another bonus is that because the game is now ostensibly a Windowed desktop application, switching to other applications (say for example if you use dual screens) means the systems doesn't need to switch from true full screen back to the desktop, which prevents the delay associated with doing this. This means you can muck around with other applications while waiting in lobbies and so on without undergoing the annoying fullscreen/window switching delay.
Worth noting is that after you do this once, provided Borderless Gaming is running, it will remember the settings every time you run SFIV.
I strongly recommended against enabling vsync in-game once this is in effect (nor is it required anyway). There seems to be a weird bug with SFIV that sees Oni and Evil Ryu's aura effects invoke a really weird stuttering issue that breaks this 'fix'.
* Some games don't agree with Borderless Gaming. For example, Quake Live absolutely refuses to play ball and I had a shit of a time getting GZDoom to bite consistently. SFIV works nicely though. Ideally I'd like to get my hands on a UE4 driven game to see if this is something perhaps useful for when SF5 drops also.
Give this a shot and see what you guys think. One thing to keep in mind that every millisecond shaved off local input lag transfers to a bump in responsiveness for online play also. While it naturally doesn't reduce online connection
lag whatsoever, the small boost in response you receive for your local inputs naturally eats into the total frame delay (offline input latency + incurred online play lag) making for a better experience overall.
At least, this has been the experience for myself.
For those curious, I run all these tests and so on using a desktop machine running Windows 7 driven by an nVidia GTX 970 card.
Guacamole is awesome.