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Thread: Elgato Cam Link 4K in Google Meet, Zoom etc

  1. #1
    Join Date
    Jun 2020
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    3

    Elgato Cam Link 4K in Google Meet, Zoom etc

    After a bunch of fiddling I just got this working, so figured I'd post the magic incantation here for posterity, as well as how I cracked it. I have an Elgato Cam Link 4K hooked up to a Panasonic Lumix DSLR, so I get that beautiful soft focus in remote meetings. It worked nicely in MacOS but I didn't have much luck in Ubuntu: programs would detect /dev/video0 and /dev/video1 but it would just never work. FFmpeg said something about corrupted bytes.

    The camera DID work fine in OBS Studio though. So I started OBS from the command line and took note of the stuff it spewed in the log, most notably "50fps", "yuy", and "1920x1080". I googled ffmpeg's various pixel formats and it had one called "yuyv422".

    Next thing I got from another forum: install v4l2loopback. This creates a dummy video capture stream that you can pipe stuff to. So the magic incantation is this:

    Code:
    sudo modprobe v4l2loopback
    ffmpeg -f v4l2 -framerate 50 -pix_fmt yuyv422 -video_size 1920x1080 -i /dev/video0 -f v4l2 -vcodec rawvideo -pix_fmt yuv420p /dev/video2
    This makes ffmpeg read from the /dev/video0 stream with the options I got from OBS, and pipes it to our new dummy stream in the "yuv420p" format (which seems a little bit more standard). Now I can pick that dummy device and use it as expected!

    Hope this helps somebody from the future

  2. #2
    Join Date
    Oct 2020
    Beans
    1

    Re: Elgato Cam Link 4K in Google Meet, Zoom etc

    Thanks for posting the solution -- this helped me out!

    In case anyone else is running into this problem, I made a Python script to automate launching the relevant ffmpeg command in the background here.

  3. #3
    Join Date
    Jul 2013
    Beans
    2

    Re: Elgato Cam Link 4K in Google Meet, Zoom etc

    There is a bug in the Cam Link 4K firmware which breaks all pixel formats except the first one. I developed a quirk to fix the buggy firmware and submitted it to the upstream Linux: https://lore.kernel.org/lkml/2021032...ung@posteo.de/

    So once this patch is accepted, backported to older kernel released, and included in the Ubuntu kernel this workaround is not needed any more.

  4. #4
    Join Date
    Jul 2013
    Beans
    2

    Re: Elgato Cam Link 4K in Google Meet, Zoom etc

    The fix was accepted upstream: commit 4c6e0976295add7f0ed94d276c04a3d6f1ea8f83

    This fix was also backported to the stable releases. The fix is included
    in:

    • 4.4.276
    • 4.9.276
    • 4.14.240
    • 4.19.198
    • 5.4.134
    • 5.10.52
    • 5.12.19
    • 5.13.4
    • 5.14-rc1

    This bug tracks the backport in Ubuntu: https://bugs.launchpad.net/ubuntu/+s...x/+bug/1932367

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