Input Lag - More Testing by Brunnis

[Lordmonkus]

Brunnis over on the Retroarch has done some more input lag testing and has some very interesting results. It is a bit of a long, mathy and technical post but the TLDR version is this;

Properly setup emulators and an LCD monitor has no more input lag than an actual SNES hooked up to a CRT TV.

https://forums.libretro.com/t/an-input-lag-investigation/4407/524

[fromlostdays]

As someone who sucks at both math and reading technical posts, how about a summary of  how to "properly setup"? 

 

[Lordmonkus]

From his post:

RetroArch settings

Default, except:
video_fullscreen = “true”
video_windowed_fullscreen = “false”
video_hard_sync = “true”
video_frame_delay = “6”
video_smooth = “false”

You can adjust your frame delay and make it higher for lower lag if your CPU is fast enough for it. Brunnis said that 6 was as high as he could go on the laptop he tested on, if you go to high there will be audio crackles and slowdown.

[fromlostdays]

I did read the post, but it meant very little to me. What did catch my eye is him saying vsync doesn't add input lag. I hope that's true.. 

[Lordmonkus]

According to his tests vsync alone combined with hard gpu sync and frame delay doesn't have any added input lag. Keep in mind he is using an LCD monitor, TVs are different and have image processing hardware in them and will have input lag, especially if "Game Mode" is not enabled.

[mothergoose729]

9 hours ago, Lordmonkus said:

Brunnis over on the Retroarch has done some more input lag testing and has some very interesting results. It is a bit of a long, mathy and technical post but the TLDR version is this;

Properly setup emulators and an LCD monitor has no more input lag than an actual SNES hooked up to a CRT TV.

https://forums.libretro.com/t/an-input-lag-investigation/4407/524

I read that too, and it is very encouraging. 

There were some speculative bits in the testing. Emulator authors identify 1 -2 frames of lag inherent in their emulation, so I tend to go by that number. Emulators other than retroarch also can introduce additional overhead, depending on how they handle frame buffers and peripherals (dolphin has tested their own stuff, and identified 1 frame of lag from real hardware, or even less lag than real hardware in some cases, depending on the accuracy of the frame buffer emulation). 

With retroarch though, with a hard GPU sync and a touch of frame delay, you can expect to be within 1 -2 frames of real hardware on a CRT which is amazing.