SteamVR Valve Index frame drop & stutter - possible solution

[Crowley]

Hi all,

TL;DR - I found that frame drop and stutter in SteamVR on my Valve Index rig was caused by USB conflict with my webcam.

My rig: Ryzen 7 3700X@3.6GHz; 32GB RAM; ASUS Prime something-or-other II; RTX3060Ti (formerly GTX1660 Super); couple of bells; one or two whistles.

I'm not usually one for the forums but having seen the amount of frustration caused by frame drop & stutter, I thought I would share my experience.

I had recently replaced my GTX 1660 Super with an RTX 3600Ti (FE) - it was a bargain after the 40xx release! - and did not notice any immediate problems when playing in VR (including Half Life: Alyx; super-modded Skyrim; Star Wars Squadrons, Elite Dangerous)

More recently I upgraded to Windows 11 and added a 2TB SSD to replace my existing game drive.

First time I fired up VR I noticed frame errors and drop which created the worst kind of stutter, even in SteamVR Home:

https://steamcommunity.com/sharedfiles/filedetails/?id=2904831913

Skryrim was just about playable but the stutter seriously annoying; HL: Alyx was a disaster. It took 5 mins to get to the start menu, which was so laggy it was impossible to even navigate to load a game. The pic below says it all:

https://steamcommunity.com/sharedfiles/filedetails/?id=2904832424

i scoured the Internet and top problems in the forums are Windows 11 and NVIDIA drivers. I tried all of these things, and none of them worked:
- rolled back to Windows 10
- Windows 10 reset
- rolled back NVIDIA divers for the 3060Ti as far as I could go
- stuck my 1660 Super back in the rig and installed the earliest drivers I could find
- clock speed / voltage tweaks in BIOS/MSI Afterburner
- changing every setting possible in SteamvR
- removed all games and reinstalled Steam
- uninstalled all overlays, game bars and monitors ( and MSI Afterburner!)
- suspended a bunch of suspicious-looking processes that might be getting in the way
- cried a little bit and pleaded with the Universe not to let it be so
Basically, if it was on a forum somewhere, I tried it, but at the end of the day: pink spikes, frame drops, stutter.

Some forums mentioned CPU throttling. I have a Ryzen 7 3700X, which, okay, is not exactly top spec, but surely enough to handle an RTX 3060Ti, and what was there to throttle at low settings in SteamVR Home?

Watching the performance graphs, however, I saw that after the first bit of fiddling, the pink spikes and dropped frames occurred at consistent intervals - like, I could have used them as a metronome and never missed a beat - but a regular beat means that something is intentionally drumming.

I used to be an IT guy back in the '90s/'00s and one very common problem back in the days of ISA was that hardware sharing the same interrupt request (IRQ) line would conflict and cause intermittent functionality, I have been out of that work for years and I thought the newbies had basically sorted that out - but - I thought, why not give it a try.

So I unplugged every USB device apart from my keyboard and the Valve Index cable. Perfect, buttery smooth VR:

https://steamcommunity.com/sharedfiles/filedetails/?id=2904833270

One by one I plugged things back in to the ports they came out of, and when I plugged my (cheap, £15) webcam back in: pink spikes, frame drops, stutter.

BUT

It only happens if I plug the camera into the 2nd port of the USB pair that my Index cable is also plugged into . My rig has 8 (technically 6) USB ports, in 3 (let's call it 4) pairs. If the camera and the Index are not in the same pair, everything is fine, but if they sit next to each other - pink spikes, frame drops, stutter.

No other device - external SSD, keyboard, speakers, 7-port USB expansion hub - causes the same conflict, but my cheap-arse £15 Amazon-bought USB Zoom cam brought a whole world of misery that I'm pretty sure, from what I've read, some other people out there have spent $thousands of £pounds trying to fix.

I operate on the law that if it happened to me, then it happened to other people, so I hope my little story helps some of the folk out there who are having this problem.

Would love to hear back if this works for you.

Cheers,

Crowley

[walllable]

I'm glad to see that you've shared your experience, solution, and insight here. I haven't really had this issue myself, but I'm glad you've posted this so that other people can have an easier time fixing the issue.

[Crowley]

Originally posted by walllable:

I'm glad to see that you've shared your experience, solution, and insight here. I haven't really had this issue myself, but I'm glad you've posted this so that other people can have an easier time fixing the issue.

Thanks! I really hope it helps 'cos it was sooooooo frustrating, and there are tons of other people out there with the same issue...