(Not Resolved) Known Issue - Quest PCVR streaming micro lags and stutter esp. when moving head

[acreed11]

Hi team,

I'm getting micro lags and stutter in Airlink on my Quest 3 (EU/UK), esp. when moving my head. In the Oculus debug overlay this causes brief spikes in transmit/decode, fps drops and visible stuttering. The issue is not present on my Quest Pro with otherwise identical settings - see below screenshots to illustrate.

Few more details:
- Issue is not present on Quest Pro with same settings on HMD, router and PC (using same res)
- Issue is worse at higher bitrates, esp. >200mbps, but still present <200mbps
- Issue is unrelated to PC/game latencies (CPU, GPU, Queue each <5ms)
- Stutters/lags are intermittent (every 10-20 seconds) when not moving but happen immediately and reproducibly when moving the head to either side or especially looking downwards (i.e. on any bigger headset movements)
- Wifi 6E router (TP Link AXE75 EU/UK)
- EDIT: exact same issue with Asus RT-AXE7800 (EU/UK) wifi 6e router
- Connection shows as 2,400mbps
- Airlink codec H264 (but same on other codecs)
- I've attempted factory resetting, installing latest drivers
- Updated to v62 and latest Quest Link desktop version (I can see the 120hz option for my Q3)
- EDIT: Ordered a separate Quest 3 for testing: presents the exact same issue

-EDIT: Same issue on 5ghz 802.11ax 160mhz BUT switching to 802.11ac (!) completely fixed the issue. I cant test this on 6ghz but looks like 802.11ax or something related to how q3 implements it is the culprit

As the issue is worse the higher the bitrate and not present on Q Pro with otherwise same settings, I suspect it's related to the below known Wifi issues - but opening a new thread as instructed. 
https://communityforums.atmeta.com/t5/Get-Help/Known-Isssue-Unstable-wifi-coverage-with-Quest-3-on-s...

Best,
JensQ3QPro

Updates:
- Tried separate router: exact same issue with Asus RT-AXE7800 wifi 6e router
- Ordered a separate Quest 3: exact same issue on both routers

-Same issue on 5ghz 802.11ax 160mhz BUT switching to 802.11ac (!) completely fixed the issue. I cant test this on 6ghz but looks like 802.11ax or something related to how q3 implements it is the culprit

[alexlighthill]

I've discovered that MSI Afterburner with RivaTunerStatisticsServer cause some framerate drops, but still it is not the main problem in my case.

[D3ft0ne]

Ya I never have that enabled when using Air Link or VD. Hoping for the fix sooner than later, since the issue is very obv. For now VD at least works way better.

[acreed11]

Yes, forgot network, rebooted headset, reconnected to WiFi. No change

[KeyMag]

What router you have?

I tested on Mercusys MR80X on Qualcomm and TP-Link Archer AX80 on MediaTek. On both it help.

[D3ft0ne]

He mentions in the issue description - he has axe 75 and axe 7800.

Though what your fix provides is more stable consist download / upload speed over wifi 6e which is great... BUT, did you test encoder stutter / lag when playing a game... Like original poster reports? Those might not even be related. 

[acreed11]

Hi team, important finding:

I'm getting the same issue on 5ghz 802.11ax 160mhz BUT switching to 802.11ac (!) fixes the issue (same 5ghz 160mhz). Obviously not really a solution but workaround for the time being.

I can't test this on 6ghz (router can't switch to ac there) but looks like 802.11ax or something related to how q3 implements it is the culprit.

[007x007]

Just curious of Your testing method. Do that way are reliable to test packets loss? UDP are not guaranted to be received or with sent order in perfect environment and it's OK for UDP.

For example You can send UDP  packets with order: 1,2,3,4... and receive: 2,1,3,4.... By simple checking if next packet number is higher than previous will give false-positive alarm.

[VirtualOmnipresence]

The unordering of UDP packets usually occurs in more complex networks (like the internet) where a packet can go multiple routes. If e.g. packet 5 takes a faster route than packet 4, you will receive packet 5 before packet 4. I haven't seen this happening in a single Wifi router setup yet as there is only one route for the packets to take (the one over the Wifi router).

Anyway, in my video I'm comparing the Quest 3 directly with the Quest 2 which shows zero packet loss even though it's using the exact same software and networking setup. So it's definitely not a problem introduced by the test setup, but clearly something that is introduced by Quest 3.

[007x007]

Seems logical. Just thinking if maybe in Quest 3 packets are not lost, but arrive later. Anyway result will be same, delays which will cause lag spikes.

[acreed11]

@MetaQuestSupport could you please ACK you've seen and passed this on?

Appreciate any general status update on this - thank you!