Capturing 2160p Without Stutter?

[Mary-Jane Rottencrotch]

I recently bought a Raspberry Pi 4 model B 4GB in the hope I could replace my old Steam Link hardware with something that could handle 4K streaming.

I can get Steam on my desktop to capture at 2160p but only when the Steam Link app on the Pi 4 has HEVC enabled. However, whenever I have HEVC enabled I get slight artifact glitches every second across small areas of the screen.

I can drop the capture resolution down to 1080p (2160p captured at 1080p) and it still happens. I can drop the desktop resolution down to 1080p and it happens (1080p captured at 1080p). When I turn off HEVC I can stream 2160p captured at 1080p without the stutter every one second but when I try to set the capture resolution to 2160p it gets set back to 1080p. I assume this is because HEVC is required for the streams higher than 1080p.

Changing the client options between Fast, Balanced and Beautiful doesn't make a difference with HEVC. It glitches even on Fast.

I have the Pi and desktop on the same LAN connected via gigabit switches. Both report link speeds of 1000Mbps. The ping latency across the network between them hovers between 0.3ms to 0.7ms. This to me indicates the network is fine and it is something to do with the Pi.

Has anyone else managed to stream 2160p to the Pi 4 without this stutter?

*EDIT*
I've just been able to test between another desktop connected to a 4K TV and there is no stutter so I know the hosting desktop is fine and it is Pi related,

Another question is how do I tell Steam to do 2160p 60Hz instead of 2160p 30Hz?

*EDIT2*
I've tested the link speed between the Pi and the desktop and it averages at 940Mbps.

I also shouldn't call the issue a stutter. It only happens to certain areas of the screen depending on what is visible. A static image will glitch in the same areas every time so it isn't something struggling otherwise the glitching would be random across the screen. This is the same thing each second. Really annoying because it is so close to working.

I've tried to capture the issue on my phone but as it only does 30fps it's hard to capture. I also think Vimeo's transcoding didn't help. I'll try another camera later if I get chance.
https://vimeo.com/637820969

*EDIT3*
A slightly better video of the issue but it still misses a few instances because the frame rate isn't in sync.
https://vimeo.com/637876416

I've just ordered a fan and heatsink for the Pi so I can rule out cooling issues.

*EDIT4*
Fan and heatsinks added. Temperature before I added everything averaged around 64c after a few hours using Steam Link streaming 2160p 30Hz. After adding them it is now averaging at 34c after a few hours use which is great. However, the issue isn't resolved.

I'm going to purchase the official Pi 4 power cable as that could be the issue. I should have just bought it to begin with but I'm a cheapskate. I've bought a case, fans and heatsinks via separate deliveries that combined still don't cost as much as that cable. Ah well.

*EDIT5*
Official power cable for the Pi 4 didn't resolve the issue. I did get 4K 60Hz working on the Pi though. However, when I have 4K 60Hz on the Pi Steam still captures 2160p at 30Hz and I don't know how to change this? Also, when the Pi is set to 2160p 60Hz, Steam no longer streams the 2160p resolution correctly. I just get the top portion of the hosts screen. This has turned into quite a nightmare.

All I really need to know is if anyone has ever got the Pi 4 to stream 2160p via Steam Link without issue?

*EDIT6*
So, I have the Pi 4 running at 2160p 60Hz and I have Steam streaming at 2160p with a frame limit of 60fps. Everything works well expect for this glitch. Guess I'll have to wait for more updates to the Pi in the hope something is improved. :(