Latency with Pi 4 B - H264 decoder?

[civwar99]

Hi,

I have been experiencing latency of what feels like ~1/4 second when using Steam Link on a Pi 4 Model B. This is from pressing a button on the controller to a response on the screen.

Having carefully eliminated likely causes, it seems that the latency could be due to the video decoder. By default Steam Link is using "Raspberry Pi hardware decoding" however if I enable HEVC then the decoder switches to "MMAL ffmpeg hardware decoding" and the latency disappears.

Unfortunately enabling HEVC causes the Streaming Latency to increase and other artifacts so isn't really a solution.

Has anyone else seen this? Is this expected behaviour with Steam Link and the RPI4B or is there perhaps a fix?

Thanks for any help!

[civwar99]

Thanks for the tips Xenophobe, I'll try that out as soon as I can.

[civwar99]

I tried setting the bandwidth to 25 Mbps, the resolution to 1920x1080, and the GPU split to 512 however the latency is still there. If I keep the settings exactly as they are and enable HEVC then the latency disappears.

Xenophobe, do you have Steam Link working on a RPi4B with H264 and no latency? For me it's only noticeable on platformers e.g. Sonic Mania. With H264 there is a clear pause before Sonic jumps, with HEVC it is practically instantaneous.

Thanks again for the help!

[civwar99]

I've tried upgrading and that brought in the new vlc packages but sadly still no improvement. That's really interesting that you're not having issues on the 3B+, I don't need 4K either so might see if I can exchange the 4B. Thanks!

[civwar99]

Yeah good point, assuming it is specific to the RPi4b then it'd be great to know if the devs are aware of this being a known issue. My RPi3b+ should be here on Friday so will try it out and see if it makes a difference :-)

I've seen it on multiple Sonic games but not on other non-platformer games although I think that's just me not being experienced enough on those games to recognise it.

[civwar99]

The RPi3b+ was the same unfortunately however I think I've identified the issue!

The games I've been playing aren't being captured at the output resolution of the Pi e.g. the default Sonic Mania resolution is 848x480. If I change the Sonic Mania resolution to 1920x1080 then it works great and there's no latency any more. I tried 1280x720 as well and that's better than 848x480 but it still feels like there's a slight delay.

Thanks for the help Xenophobe, really happy to get it working!

[civwar99]

Do you know if that's mentioned anywhere? I haven't had the problem when playing from other Steam Link devices so it seems that it might be a Pi specifc issue. I've only tested at 1080p but they both seem to work just as well as each other :)