Slow framerate, high latency, input lag during Remote Play of Vulkan games on Ubuntu to Steam Link (SlowGamePercent)

[Davidian1024]

Your system information

• Steam client version: Steam Beta Branch: Stable Client Steam Version: 1718904662 Steam Client Build Date: Thu, Jun 20 1:14 PM UTC -05:00 Steam Web Build Date: Wed, Jun 19 8:04 PM UTC -05:00 Steam API Version: SteamClient021

• Distribution: Ubuntu 22.04.4 LTS Jammy Jellyfish

• Opted into Steam client beta?: No

• Have you checked for system updates?: Yes

• Steam Logs: steam-logs.tar.gz

• GPU: Nvidia GTX 1080Ti

Please describe your issue in as much detail as possible:

When I stream games to a Steam Link device (I have tested with a Raspberry Pi 4B and an Androind phone) I get very low FPS for any Vulkan based game. Games using OpenGL seem unaffected. I think all of the games I run with Proton are affected by this. I think those all use Vulkan now.

In ~/.local/share/Steam/logs/streaming_log.txt I see lines like these: Slow framerate: game 45.95, capture 0.51, convert 0.01, encode 13.89, network 9.30, decode 1.67, display 7.88 (game) Followed by a SessionStats section that mentions SlowGamePercent with a number that's usually above 20. While all the other Slow...Percent stats are 0.

I can most easily determine which games are using Vulkan or OpenGL with the Remote Play Client Details Performance Overlay. For Vulkan games the encoder is reported as Game Vulkan NV12. For OpenGL games is is Game Delayed OpenGL NV12.

I have tried many many different combinations of both advanced host and client options under Steam's Remote Play settings. Nothing seems to improve the situation when streaming Vulkan games.

Steps for reproducing this issue:

Launch a Vulkan based game directly on the Ubuntu host with the Steam In-game FPS Counter enabled. Observe a high framerate. Launch the same game on the same host through a Steam Link device. Observe a low framerate.

Games I've spent the most time testing with: Vulkan Games (Encoder: Game Vulkan NV12)

• Cuphead (Vulkan): Directly on the host FPS: ~60. Streaming to either Steam Link device: ~22FPS.
• Trackmania (Vulkan): Directly: ~150. Streaming to Steam Link: ~22FPS.

OpenGL Games (Encoder: Game Delayed OpenGL NV12)

• Celeste (OpenGL): Directly on the host FPS: ~60. Streaming to either Steam Link device: ~60FPS.
• Angry Video Game Nerd I & II Deluxe (OpenGL): Directly on the host FPS: ~60. Streaming to either Steam Link device: ~60FPS.

For what it's worth I see roughly the exact same FPS for any Vulkan game when streamed to any of my Steam Link devices. It's almost always 22FPS or very close to that number.