Logitech C920 Works on ChromeOS, but not on Linux?

Posted by JD 06/02/2016 at 17:00

Logitech C920 Works on ChromeOS, but not on Linux? Huh?

Be certain to read the last paragraph. It started working and has been solid.

For the last 4 months, I´ve had a chromebook running ChromeOS because I hadn´t figured out how to get it to boot Linux with an encrypted SSD off the internal drive. Solved that last week (completely removed the write-protect screw) and was surprised that the Logitech C920 which has been working under ChromeOS perfectly for all these months doesn´t work at all under Ubuntu-Mate 16.04.

Under 16.04, on the chromebook, the webcam is seen and known.

$ lsusb
...
Bus 001 Device 006: ID 046d:082d Logitech, Inc. HD Pro Webcam C920
...

and

$ dmesg |grep -i webca
[ 2003.745906] usb 1-2.3: Product: HD Pro Webcam C920
[ 2003.746473] uvcvideo: Found UVC 1.00 device HD Pro Webcam C920 (046d:082d)
[ 2003.747715] input: HD Pro Webcam C920 as /devices/pci0000:00/0000:00:14.0/usb1/1-2/1-2.3/1-2.3:1.0/input/input12

So it appears that it should work. Let´s check some permissions …

$ ll /dev/video*
crw-rw----+ 1 root video 81, 0 Jun  2 09:57 /dev/video0
crw-rw----+ 1 root video 81, 1 Jun  2 10:30 /dev/video1

The built-in webcam for the chromebook is working – same permissions, owner, group. The C920 should work too.
Looking a little closer … lshw:

                 *-usb
                      description: Video
                      product: HD Pro Webcam C920
                      vendor: Logitech, Inc.
                      physical id: 3
                      bus info: usb@1:2.3
                      version: 0.11
                      serial: 76B4D93F
                      capabilities: usb-2.00
                      configuration: driver=snd-usb-audio maxpower=500mA speed=480Mbit/s

only audio? Hummmm. The built-in webcam uses the uvcvideo driver. So I need to find and load the correct driver. Need to get ChromeOS booting for this machine so I can steal the driver, I guess.

On 14.04, I got the C920 working for about 20 min at a time. Then the video would get wonky. Not good.

Update a few days later …

So after a reboot of the Ubuntu-mate 16.04 box, the C920 webcam started working. To test the stability, I loaded up Open Broadcaster System and recorded 3 hrs of room activity with audio from the webcam too. The image wasn´t perfect and I didn´t use 1080 resolution since my main goal is to capture presentations – that means muxing 2 audio sources (speaker and crowd) with 2-3 video sources (talking head, presentation slides and perhaps crowd video). The talking head part will likely be a tiny square in the corner with the slides, so resolution doesn´t need to be huge. OTOH, the slides need to be 1080p for readability. I don´t capture that feed in OBS live; use an external capture device for that instead.

Should point out that my $35 USB Sansom Go Mic microphone (WONDERFUL!!!!!) is still working. Also have a $22 20 ft lapel mic working through the headphone jack, but the C920 microphone is only slightly worse, so doubt it will be used much.