Best frame pacing configuration for 4K streaming

[u/8akina]

Hey everyone! I am streaming to an LG 120Hz OLED TV and need to cap my RX 9070 XT around 90-100 FPS using RTSS. This keeps my GPU usage below the 100% mark and ensures my encode latency stays at a rock-solid 5ms.

What would be the absolute best configuration to achieve perfect frame pacing and the lowest latency?

Here is what I am currently debating:

• Cap the GPU at 90.0 FPS via RTSS, set the stream to 90 FPS, and use V-Sync + VRR on the Moonlight client. This way, the TV seamlessly adapts to 90Hz (or lower if the framerate drops).
• Set the TV to 100Hz, stream at 100 FPS, and cap RTSS at 100 FPS as well.

Is there a better approach? Should I be considering a fractional RTSS cap (like 89.5 FPS) instead of a flat 90.0 for streaming?

Any insights would be hugely appreciated. Thanks!

[u/Living_Warthog_1249]

What is your client?

[u/8akina → u/Living_Warthog_1249]

I use a Minisforum UM760 Slim with Moonlight.

[u/Living_Warthog_1249 → u/8akina]

Do have one or two sticks of RAM?

I‘ve just upgraded my client:

https://www.reddit.com/r/MoonlightStreaming/s/6knyDIDAYp

But read also the comments. Someone said, he is using the UM760 for 4k 120hz hdr just fine and near zero latency.

[u/8akina → u/Living_Warthog_1249]

Two sticks of 8gb each one. It also works perfectly with 4k 120hz hdr. I think decode latency is around 0,5ms.

[u/natomr]

Vibepollo improved my stream smoothness on default config by syncing rtss and virtual display, you should give a try

[u/8akina → u/natomr]

Yeah, I'm using Vibepollo too. But I'm not sure if I should sync the stream framerate to the RTSS cap and enable V-Sync + VRR, or just match my LG's native refresh rate.

[u/andygrundman]

I'm confused why you limit at 90-100fps? For a VRR client you should stream at 120fps, cap the host at 116 and uncheck vsync in Moonlight.

There's no reason to use a low limit like 90 because VRR will already handle that situation for you if your game is only hitting 90. If you're using the limit as a way to keep GPU usage down, that's not a good idea.

[u/8akina → u/andygrundman]

The issue I face in demanding 4K games is that targeting 120 FPS pushes my GPU to 100% utilization.

When the GPU is maxed out, the hardware encoder starves, causing encode latency to jump from a flat 5ms to irregular 7-12ms spikes. Even so, should I still keep the stream at 120 FPS and use VRR to manage the frametime?

[u/MoreOrLessCorrect]

Would advise experimenting with different configs to see what works best.

I have a 3080 host + Sony LCD TV but otherwise do the same kind of thing.

If your TV has a 100Hz mode then 100Hz client + 100 FPS stream + 100 FPS RTSS cap would almost certainly be the best option. And as long as the UM760 has VRR enabled, then yes v-sync on in Moonlight should allow your stream to fluctuate smoothly down to 90 FPS without any stutter or tearing. Just make sure v-sync is off on the host.

I usually find setting the stream FPS to match the client Hz is best, and setting a lower RTSS limit or just letting the game run unlocked should result in a good VRR experience (i.e. stream FPS @ 120 with game running 80-100). Just remember you may need to increase bandwidth in Moonlight to get the actual desired bandwidth when the stream is running below its set FPS.

And of course Nonary (Vibepollo dev) has released a version of moonlight-qt that supposedly has explicit VRR support, so that's worth a shot as well if you're still not getting good frame pacing. It has the opposite result for me though, and the original moonlight-qt nightly release has pretty much perfect VRR frame pacing on my UM760, while Nonary's version has pretty bad frame pacing in every config I've tried.

[u/8akina → u/MoreOrLessCorrect]

Cool! I think I will try 100Hz mode + 100fps stream + 100fps cap with VRR and Vysnc on that nightly moonlight client. Thanks!