[FS-UAE] Heavy input lag with VSync

[RealNC]

I didn't follow the emulation scene much in the last couple of years. I was surprised to see the two new emulators (FS-UAE and PUAE). I'm running Linux (Gentoo 64-bit).

I downloaded FS-UAE today (Git master) and it built OK. However, VSync results in quite severe input lag. The mouse for example is very, very "floaty" and input from my gamepad takes a very noticeable amount of time before it shows an effect in the game. For stuff like Monkey Island and other "slow" games, this is OK (just a bit annoying, but it's still playable.) Fast action games however suffer from this. Forcing "video_sync = off" makes the problem go away mostly. "vblank" instead of "full" or "auto" also doesn't help. I tried all "video_sync_method" options, but it doesn't help. 50Hz vs 60Hz doesn't make a difference. Enabling/disabling triple buffering in the NVidia driver (Option "TripleBuffer" "False/True") doesn't make a difference either.

WinUAE (and other applications, like SNES, BSNES, Nestopia) don't seem to have this problem (at least not in this magnitude; there's always a tiny bit input lag with VSync.) I didn't try PUAE, since it doesn't compile for me.

[FrodeSolheim]

Hi! It is not normal to have "severe input lag" like you describe (I have not noticed this myself).

One possibility is that your computer is to slow to run the emulation at full speed?

If you have a decent computer, and you run full vsync @50Hz, you can try the option "low_latency_vsync = 1" (with the development version). Currently, full vsync uses a "pipelined" approach where a new frame is calculated while the last one is rendered, which increases performance but introduces ~20ms extra input lag. With "low_latency_vsync = 1", a frame is calculated and then rendered, and a new frame is not calculated before after vblank.

[RealNC]

Originally Posted by FrodeSolheim

One possibility is that your computer is to slow to run the emulation at full speed?

I'm using a 2500K CPU that runs FS-UAE at 3.7GHz in turbo mode. I guess that would be adequate

If you have a decent computer, and you run full vsync @50Hz, you can try the option "low_latency_vsync = 1" (with the development version). Currently, full vsync uses a "pipelined" approach where a new frame is calculated while the last one is rendered, which increases performance but introduces ~20ms extra input lag. With "low_latency_vsync = 1", a frame is calculated and then rendered, and a new frame is not calculated before after vblank.

Thank you. This actually helped quite a bit I don't know why 20ms looked "heavy" to me, but it did.