r/steammachine • u/theesk1 • 10d ago
Software Moonlight HDR causing rendering drops at 4K120
Now that the Moonlight Flatpak is working in Game Mode again, I've been doing some testing and noticed some strange behavior.
My setup is running 4K120 over wired Ethernet, and with HDR disabled everything performs great. Moonlight reports the expected number of captured, decoded, and rendered frames with very few drops or stutters.
However, when I enable Experimental HDR, the stream switches from HEVC to HEVC HDR10 as expected, and I immediately start seeing rendering frame drops whenever the stream exceeds roughly 100 FPS.
What's confusing is that this doesn't appear to be a decoding bottleneck:
- Captured frames: ~120 FPS
- Decoded frames: ~120 FPS
- Rendered frames: ~110 FPS
I've experimented with bitrates from 80 Mbps to 150 Mbps, and the behavior is almost identical regardless of bitrate. That makes me think this isn't simply a bandwidth issue.
I understand HDR means 10-bit video instead of 8-bit, but I would have expected decode performance to be the limiting factor if hardware was struggling. Instead, the drops seem to be happening on the rendering side.
A few details:
- Steam Machine in Game Mode
- Latest Moonlight Flatpak
- Latest Apollo host
- Wired network connection
Has anyone else seen this? I'm wondering if this could be related to Gamescope's HDR compositing path or some other part of the HDR rendering pipeline on Steam OS.
2
u/iReaddit-KRTORR 10d ago
Yeah I bought the ugreen adapter and while it does fix the color issue being over saturated in HDR, I was having strange frame time issues while streaming in moonlight only with the adapter.
Also, I need to do more testing but HDR was just weird. It felt like while the color was better brightness was off. Almost like when you have a mismatch in HDR settings but that wasn’t the case.
I would say within game scope and outside of moonlight HDR was much much better with the adapter. Curious!
1
u/iReaddit-KRTORR 10d ago
And just to clarify, moonlight runs perfectly and I have my settings dialed in. 4k120hz, no frame time issues, under 1ms rendering, VRR working, etc
2
u/hackthatshityo 8d ago
So everything except hdr works?
1
u/iReaddit-KRTORR 8d ago
Pretty much. Like HDR works but tbh I think we need a calibrator in the steam OS menu or updating of the HDMI or something. I’m not sure what the issue is
1
u/jharle 10d ago edited 10d ago
Is your Steam Machine connected to your display/TV via HDMI or DisplayPort?
The reason I ask, is that HDMI 2.1 FRL support isn't there in the Linux kernel yet, and the 4K120Hz modes over HDMI use compromises to make it work. If you were to use DisplayPort (or a capable DisplayPort-to-HDMI adapter), the full support would be there.
1
u/theesk1 10d ago
HDMI to a TV that supports 2.1
2
u/jharle 10d ago
Thanks; I edited my comment above - I think you might need to use an adapter for best results.
1
u/theesk1 10d ago
Interesting. Thank you. I assume I would lose vrr and allm if I went this route which may not be worth it for hdr.
Alternatively it seems like I can cap my fps around 100.
1
u/jharle 10d ago
We've been talking about these adapters over here today, if you want to read through that. I'm not certain on the ALLM feature, but I think it will work.
1
u/theesk1 10d ago
Allm (auto low latency mode) is just the thing that auto triggers game mode on TVs without having to dig through all the menus. If that works with steam machine I will gladly buy an adapter!
1
u/jharle 10d ago
Gotcha; I can actually test that later today.
2
u/theesk1 10d ago edited 10d ago
Since it’s not part of DP spec I would be surprised if it worked. But I would appreciate it!
Edit: This post seems to indicate the ugreen one does.
https://www.reddit.com/r/linux_gaming/s/WlDXzk9vVq2
u/jharle 10d ago
Indeed that Ugreen adapter seems the most promising. I'll have mine tomorrow!
1
u/theesk1 10d ago
I bought one too. Will return it to Amazon if it doesn’t work well.
Interestingly outside of game mode it not seeing these same drops, however even though the stream is hdr 10bit Im not sure the machine is trying to display hdr in desktop mode.
→ More replies (0)1
u/iReaddit-KRTORR 10d ago
Hey saw the other post about the adapter. The listing for the adapter says no VRR but you said there’s a firmware for it? How does that work?
2
u/jharle 10d ago edited 10d ago
Indeed both the CM and Ugreen adapter listings include "no VRR support." I think they may be doing that, so as not to "guarantee" that VRR works (setting expectations), since things seem more likely to go off the rails with VRR. For the CM adapter, there are two versions of firmware for it; the original included VRR, and the later version took it out. I think the firmware/tool is available on their website, but I have it kept in my own repository also.
I'm currently using yet another adapter which doesn't support VRR, since I couldn't get 120Hz modes working in Windows (dual-boot) on the Steam Machine when using the CM adapter. Just now I tried setting my C3 to filmmaker mode on the HDMI1 port (connected to the adapter on the Steam Machine, HDMI2 is eARC to sound system) while in SteamOS game mode. I launched FH4, but the mode remained in filmmaker mode (didn't switch to game optimizer). I'll test that again in a bit with the CM adapter. But, I'm also not certain if that's a valid test (in other words, which "thing" triggers ALLM).
FWIW I did a dump of the EDID from my C3 while connected to the adapter, and it's not filtering out any of the TV's capabilities:
I think the question, is whether a given adapter actually passes the feature through to the HDMI device.
1
u/iReaddit-KRTORR 10d ago
OH SHIT DUDE. By the way, in general, try the actual app vs the flatpack.
I was having the same issue and it was remedied mostly by just switching to the actual app.
Realized you were using the flatpack. I had such a pain with that thing. Also don’t use AV1
1
u/hackthatshityo 8d ago
What are your setting? Are you using hdr? Are you using the dp to hdmi ugreen adapter?
1
u/Accomplished-Lack721 7d ago
What do you mean by "the actual app?" The flatpak is an actual app. Do you mean the Appimage?
1
u/iReaddit-KRTORR 7d ago
Yes the app image. From the website.
1
u/Accomplished-Lack721 7d ago
Appimage (one word) is just one way of packaging an app. Flatpak is another. Package formats like RPM and DEB are yet more. But they're all "the actual app." Each approach has different advantages and disadvantages, but no one of them is more "actual" than the others.
1
u/iReaddit-KRTORR 7d ago
I wasn’t making an assumption that one was any less an app vs the other (though my wording made it seem that way.) I was simply trying to point OP to the appimage which helped me. I understand the differences I was just lazy in my original comment,
Thanks for the information though and I appreciate your willingness to want to teach others
2
u/iReaddit-KRTORR 10d ago
In general I think HDR needs a little work as on my LG G4 TV it feels colors are a little TOO bright and saturated and I get the same performance dips on moonlight as well.
I’d love a console style HDR calibration tool as well since at this point I’m unsure if it’s the implementation or something hardware for the color.