The problem

Hi, I have a Sunplus USB Camera (Siri A9 UVC) and I'm trying to use it as a PC webcam. No matter what I try, it is visible in v4l2 however breaks apps using it. Ex., Cheese stalls when I switch to the USB camera.

As a test, i used fswebcam to take a picture. It stalls for a while, then outputs this:

karol@karol-hp2:~$ fswebcam --jpeg 85 -d /dev/video2 web-cam-shot.jpg
--- Opening /dev/video2...
Trying source module v4l2...
/dev/video2 opened.
No input was specified, using the first. (here stalls)
Unable to find a compatible palette format.

On Win10 (on the same laptop), the camera works without any problems. However here, not only does it break apps using it, but it also breaks pulseaudio. When the camera is plugged in, all my audio devices disappear from settings.

System

I'm using Ubuntu 21.04;
Kernel version - 5.11.0-34-generic

Device / Driver specifications:

USB device(lsusb):

Bus 001 Device 008: ID 04fc:6333 Sunplus Technology Co., Ltd Siri A9 UVC chipset

Hardware specs(lshf):

*-usb:1 description: Video product: Mass Storage vendor: iCatchtek Co Ltd physical id: 2 bus info: usb@1:2 version: 1.00 serial: 01.00.00 capabilities: usb-2.00 configuration: driver=snd-usb-audio maxpower=100mA speed=480Mbit/s

v4l2 devices (v4l2-ctl --list-devices):

'OBS (platform:v4l2loopback-000): /dev/video13
Mass Storage (usb-0000:00:14.0-2): /dev/video2 /dev/video3 /dev/media1
HP Wide Vision HD Camera: HP Wi (usb-0000:00:14.0-5): /dev/video0 /dev/video1 /dev/media0

Finally, v4l2 camera details (v4l2-ctl -d 2 -D):

Driver Info: Driver name : uvcvideo Card type : Mass Storage Bus info : usb-0000:00:14.0-2 Driver version : 5.11.22 Capabilities : 0x84a00001 Video Capture Metadata Capture Streaming Extended Pix Format Device Capabilities Device Caps : 0x04200001 Video Capture Streaming Extended Pix Format
Media Driver Info: Driver name : uvcvideo Model : Mass Storage Serial : 01.00.00 Bus info : usb-0000:00:14.0-2 Media version : 5.11.22 Hardware revision: 0x00000100 (256) Driver version : 5.11.22
Interface Info: ID : 0x03000002 Type : V4L Video
Entity Info: ID : 0x00000001 (1) Name : Mass Storage Function : V4L2 I/O Flags : default Pad 0x01000007 : 0: Sink Link 0x02000010: from remote pad 0x100000a of entity 'Extension 3': Data, Enabled, Immutable

1 Answer

Many device access problems can be resolved through group membership changes.

Specifically, if ls -l shows that the group permissions (the second "rwx" triplet) is "rw" (e.g."-rw-rw----"), then, adding oneself to the group that owns the device will grant rw access.

Here's how:

device="/dev/whatever"
sudo adduser $USER $(stat -c "%G" $device)

This allows you membership in the group that can rw the device, but there is one more step.

To make all your processes members of the new group, logout and login. Group memberships are set up at login time.

To create a single process in the new group (for testing, prior to logout/login):

newgrp $(stat -c "%G" $device) 

or, just type the group name. See man newgrp.