cancel
Showing results for 
Search instead for 
Did you mean: 

Disabling SPUD lowers Motion-to-photon latency?

Espionage724
Expert Protege
I have a CV1. With defaults (SPUD enabled), the lowest latency I see is about 19.40ms. If I disable SPUD via the registry, the lowest latency drops down to something in 15ms. I'm wondering if anyone else can reproduce this.

How to see Motion-to-photon latency:
  1. Run Oculus Debug Tool (C:\Program Files\Oculus\Support\oculus-diagnostics\OculusDebugTool.exe)
  2. Visible HUD -> Performance
  3. The HUD is only shown in the headset/HMD view (not desktop)
  4. Motion-to-photon latency should be the first statistic shown

How to disable SPUD
  1. Open Registry Editor (regedit)
  2. HKEY_LOCAL_MACHINE\SOFTWARE\Oculus (do New -> Key at HKEY_LOCAL_MACHINE\SOFTWARE if Oculus doesn't exist)
  3. New -> DWORD (32-bit) Value -> UseSpud
  4. Keep it at 0
  5. HKEY_LOCAL_MACHINE\SOFTWARE\Oculus\UseSpud should be a DWORD set to 0
  6. Go to %LocalAppData%\Oculus\Spud and delete all files (likely a .spud and some mashed file)

How to test Motion-to-photon latency:
  1. SPUD should be enabled
  2. Do the above to enable the HUD
  3. Start Beat Saber (preferably in Oculus native mode)
  4. On the health/warning screen, observe the Motion-to-photon latency after about 5 seconds (ideally around 19-25ms)
  5. Disable SPUD (enable or disable it to compare latency numbers)
  6. Go to desktop Oculus Client -> Settings -> Beta -> Restart Oculus
  7. Re-do the steps to show the Performance HUD (toggle Visible HUD to None and then back to Performance)
  8. Start Beat Saber again
  9. On the health/warning screen, observe the Motion-to-photon latency (with SPUD disabled, should be lower around 15-17ms)

Other info:

Any game/app can be used to test latency as long as it ideally leaves a decent amount of performance headroom and is easy and quick to get to
I get lower latency in all games (tried Pistol Whip and Until You Fall; both go to about 15-16ms with SPUD disabled)
I'm unsure if SPUD has any effect on other Oculus HMDs aside from the CV1
If SPUD is disabled, the mashed file shouldn't re-appear in the Spud folder
Quest 2 | 2700X | 6600 XT
2 REPLIES 2

TomCgcmfc
MVP
MVP
I've use this Spud off process for a long time now.  For me it does not seem to do much anymore but it does help a little bit by reducing some greyish smug in very dark environments like X Plane 11 night flying.  I did test it on/off and I did also see a minor improvement like you saw.  Only a few ms difference so I don't think it makes much difference performance wise.

Just a couple of comments;

You should stop oculusruntime services before editing your reg file.  I use OTT to do this.

It's not necessary to delete the spud files.  The spud file will come back anyway and the mash file will come back if you turn spud back on.

Still pretty useful to turn it off imho.  Probably depends a bit on your headset.  Some seem to work better on/off than others.  Probably luck of the Oled draw, lol!

Edit; forgot to mention, you can go back to spud = on by either changing the reg key value to = 1 or just delete the Oculus key you created.
i9 13900K water cooled, RTX4090, Z790 MB w/wifi6e, 32Gb 6400 ram, 2x2TB SSD, 1000W PSU, Win 11, QPro, Q3, w/Link and Air Link, Vive Pro1 with Etsy lens mod and Index Controllers

Espionage724
Expert Protege

This still works nicely on CV1s in 2022! Latency is still lower with SPUD disabled.

Quest 2 | 2700X | 6600 XT