Hello.
New CL user here with a first question / help situation. Let me explain first what exactly a problem. I’m using PC for online streaming, recording with OBS Studio using four usb Elgato video capture cards connected to four SLR cameras giving me four different angles. By experiments I figured that it’s crucial to have capture cards connected to usb ports which is on separate lanes to have a smooth and stable video signal from the cameras. So just to answer some might appearing questions hardware wise. Yes it is exactly same camera models with exactly same settings, exactly same HDMI cables and exactly same capture cards with exactly same OBS setting for each ones.
And after connecting everything and starting streaming everything is fine and as it suppose to be. But after sometime one of the cameras starting occasionally dropping few frames for a 10 - 20 seconds and gets back to normal but because of that cameras is getting out of sync with each other. It’s happening randomly with different cameras, not with some particular ones. So I presume that it is not hardware related. It’s like some buffer gets overflowed or something. Sometimes even for an hour stream is perfect but frame dropping could happen anytime and it is happening unfortunately.
Before Clear Linux I tried other distros, tried different kernels, different governors and Clear Linux giving me the most longest time before lags are occurred. And I really want to stay with CL. Same problem with Macos and Windows 10 and 11. But I’m not a big fan of MS OS’s anyway.
I’m linux user for a past 10 years still can’t call myself an expert, advance user may be. I tried to research this for a while with no working solutions so far. Checked with OBS forum as well and people saying that OBS is just works with whatever signal it’s getting from capture device. Also noticed that under the wayland frame dripping is less because of the smoother desktop animation and between apps switching. X11 is fine unless you are always on OBS app without going to other desktops or windows.
I know that linux is probably the only system where everything is possible. So, is there anything I can do to get rid of this? Somebody with a knowledge how to optimize stability of USB through-output have any idea on that? Will appreciate any advice.
Thank you in advance.
Hi @shrisha
I hope CL works well for you. But as you said, this happens with all the operating systems you tested. It’s probably not related to the operating system.
The best I can do is help you figure out how to identify the problem.
Are you connecting the video capture cards to USB 3.0 ports or higher?
I suggest you test with fewer cameras and switching ports to check which part of your hardware is actually causing the problem. For example: i) Does the problem also happen with 3, 2 or 1 cameras? ii) Does the problem happen if you change the combination of USB ports that are being used?
I hope it helps.
Thank you for your reply Rene.
All capture cards are connected to USB 3.1 gen 2 ports. Means 10Gbps. Some USB A and some USB-C. All USB ports are on a separate pci lanes. I mean even if there is two ports on one lane I’m using only one of them for having all speed of this lane. Yes, it doesn’t matter it is a one or four cards are connected, frame dropping can happen anyway. Yes I tried all possible combinations to find the cause of this. Spent days for finding solution.
Linux is the best so far with my setup. A specially CL. My idea was to find bottleneck and increase the buffer of whatever casing it to fix it. There is a few things I thought about. Like UVC driver, UART of USB, OpenCV, V4L2 has buffer as well. But just few hours ago I found recommendation of one company (Allied Vision) which produce some USB commercial cameras and USB pci cards. So they recommend to increase USBFS buffer, By default it is 16 Mb. They recommend at list 1GB. I tried just with two cameras few hours ago. And was no frame drops for an hour straight in did. So tomorrow I will try with all cameras and will report here if increased USBFS buffer fixed occasional frame dropping.